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MAY.JUNE.2010.IJPM cover.2_July_August IJPM cover 4/27/2010 2:23 PM Page 1
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SHOW ISSUE
May/June 2010
Focus Issue: Microminiature Powder Injection Molding—Part II
46/3 Nanopowder Agglomerate Sintering of PIM Iron–Nickel Computer Simulations in PIM Characterization and Simulation of Mold-Filling Defects in µPIM Sintering of PIM 316L Stainless Steel Annual Technology Review: PM’s New Growth Engine
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EDITORIAL REVIEW COMMITTEE P.W. Taubenblat, FAPMI, Chairman I.E. Anderson, FAPMI T. Ando S.G. Caldwell S.C. Deevi D. Dombrowski J.J. Dunkley Z. Fang B.L. Ferguson W. Frazier K. Kulkarni, FAPMI K.S. Kumar T.F. Murphy, FAPMI J.W. Newkirk P.D. Nurthen J.H. Perepezko P.K. Samal D.W. Smith, FAPMI R. Tandon T.A. Tomlin D.T. Whychell, Sr., FAPMI M. Wright, PMT A. Zavaliangos INTERNATIONAL LIAISON COMMITTEE D. Whittaker (UK) Chairman V. Arnhold (Germany) E.C. Barba (Mexico) P. Beiss, FAPMI (Germany) C. Blais (Canada) G.F. Bocchini (Italy) F. Chagnon (Canada) C-L Chu (Taiwan) O. Coube (Europe) H. Danninger, FAPMI (Austria) U. Engström (Sweden) O. Grinder (Sweden) S. Guo (China) F-L Han (China) K.S. Hwang (Taiwan) Y.D. Kim (Korea) G. L’Espérance, FAPMI (Canada) H. Miura (Japan) C.B. Molins (Spain) R.L. Orban (Romania) T.L. Pecanha (Brazil) F. Petzoldt (Germany) G.B. Schaffer (Australia) L. Sigl (Austria) Y. Takeda (Japan) G.S. Upadhyaya (India) Publisher C. James Trombino, CAE
[email protected] Editor-in-Chief Alan Lawley, FAPMI
[email protected] Managing Editor James P. Adams
[email protected] Contributing Editor Peter K. Johnson
[email protected] Advertising Manager Jessica S. Tamasi
[email protected] Copy Editor Donni Magid
[email protected] Production Assistant Dora Schember
[email protected] Graphics Debby Stab
[email protected] President of APMI International Nicholas T. Mares
[email protected] Executive Director/CEO, APMI International C. James Trombino, CAE
[email protected]
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46/3 May/June 2010
2 Editor’s Note 5 Consultants’ Corner David Whittaker 9 PM’s New Growth Engine—Technology Development Peter K. Johnson
17 Exhibitor Showcase: PowderMet2010 FOCUS: Microminiature Powder Injection Molding—Part II 27 Full-Density Nanopowder Agglomerate Sintering of Injection Molded Iron–Nickel J.-S. Lee, B.-H. Cha and W.-K. You
37 A Review of Computer Simulations in Powder Injection Molding S.J. Park, S. Ahn, T.G. Kang, S.-T. Chung, Y.-S. Kwon, S.H. Chung, S.-G. Kim, S. Kim, S.V. Atre, S. Lee and R.M. German
49 Characterization and Simulation of Macroscale Mold-Filling Defects in Microminiature Powder Injection Molding S.G. Laddha, C. Wu, S.-J. Park, S. Lee, S. Ahn, R.M. German and S.V. Atre
61 Sintering of Powder Injection Molded 316L Stainless Steel: Experimental Investigation and Simulation X. Kong, T. Barriere, J.C. Gelin and C. Quinard
73 75 76 78 79 80
DEPARTMENTS PM Industry News in Review Meetings and Conferences Instructions for Authors APMI Membership Application PM Bookshelf Advertisers’ Index Cover: SEM of feedstock after mixing stage. Photo courtesy Thierry Barriere, FEMTO-ST Institute.
The International Journal of Powder Metallurgy (ISSN No. 0888-7462) is a professional publication serving the scientific and technological needs and interests of the powder metallurgist and the metal powder producing and consuming industries. Advertising carried in the Journal is selected so as to meet these needs and interests. Unrelated advertising cannot be accepted. Published bimonthly by APMI International, 105 College Road East, Princeton, N.J. 08540-6692 USA. Telephone (609) 4527700. Periodical postage paid at Princeton, New Jersey, and at additional mailing offices. Copyright © 2010 by APMI International. Subscription rates to non-members; USA, Canada and Mexico: $100.00 individuals, $230.00 institutions; overseas: additional $40.00 postage; single issues $55.00. Printed in USA. Postmaster send address changes to the International Journal of Powder Metallurgy, 105 College Road East, Princeton, New Jersey 08540 USA USPS#267-120 ADVERTISING INFORMATION Jessica Tamasi, APMI International 105 College Road East, Princeton, New Jersey 08540-6692 USA Tel: (609) 452-7700 • Fax: (609) 987-8523 • E-mail:
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FRONT MATTER_ FRONT MATTER 4/27/2010 2:26 PM Page 2
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EDITOR’S NOTE
T
he Show Issue of the Journal is a clear reminder that PowderMet2010, to be held in Hollywood (Ft. Lauderdale), Florida, is fast approaching on the calendar. This international event has attracted authors from 30 countries, participating in a technical program projected to consist of 34 Technical Sessions, six Special Interest Programs, and a Poster Session. All facets of PM science and technology will be addressed—from basic research to parts fabrication. The Exhibitor Showcase, included in this issue, provides profiles of all the participating companies. In the second of the Journal’s two-part coverage of microminiature powder injection molding (μPIM), the four in-depth contributions focus on full-density nanopowder agglomerate sintering and modeling/simulation. Collectively, the coverage in Parts I and II clearly demonstrates the advantages and growth of μPIM in the high-volume fabrication of small, complex-shaped components in which individual features are measured in microns. Kudos to Rand German for coordinating these two focus issues, which respectively preceded and followed MIM2010, the successful International Conference on Injection Molding of Metals, Ceramics, and Carbides, sponsored by the Metal Injection Molding Association (MIMA). The Annual Technology Review, compiled by Peter Johnson and based on input from MPIF-member companies, cites developments in PM technology that are expected to open up new opportunities for growth. Examples include advances in metal powders, PM equipment trends, and high-density parts and products. The key to this optimistic view of, and forecast for, the industry is a sustained investment in new PM technologies. In the “Consultants’ Corner,” David Whittaker, chairman of the Journal’s International Liaison Committee, again offers counsel on readers’ questions. The four diverse topics he addresses are: developments in pressing lubricants; the Global PM Property Database (GPMPD) as a source of information in fatigue design of PM components; availability of continuous cooling transformation (CCT) curves for PM steels; and expected trends for new/ expanding PM parts-fabrication plants in Asia.
Alan Lawley Editor-in-Chief
In a lighter vein, a recent New York Times Op-Chart (2/26/10) by Ben Schott cites numerous proverbs and advice for Morphean moments under the intriguing title “On the Timing and Duration of Sleep.” For your enjoyment and possible benefit I have culled the following from Schott’s collection: • Nature requires five, custom gives seven, laziness takes nine, and wickedness eleven • Eight hours work, eight hours play, eight hours sleep, eight shillings a day • To rise at five, and dine at nine, to sup at five, and bed at nine, will make a man live ninety-nine • Age can doze, youth must sleep • An hour before midnight is worth two after • He that too much loved his bed will surely scratch a poor man’s head. But he that early doth rise is on his way to win the prize. As a “morning” person, I am up and about before dawn but fade early and have frequently been accused of “resting the eyelids” during cocktails before dinner! Clearly, I can benefit from the wisdom offered by these proverbs.
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Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
FRONT MATTER_ FRONT MATTER 4/27/2010 2:26 PM Page 3
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Stain Free Solutions for PM Components The leading producer of metal powders, North American Höganäs, has introduced a series of products that address an increasingly problematic issue in component manufacturing: Stains. By the way, these products also facilitate improved lubrication, enhanced machinability, increased productivity and scrap reduction.
SM3 t4UBJO'SFF Superior machinability t Improved machinability t No detrimental effect on mechanical properties or additive corrosion resistance t4UBJO'SFF Starmix® Boost High performance t Improved ejection properties bonded mix t Excellent fill characteristics t4UBJO'SFF Intralube®E Advanced t Improved lubrication properties lubricant t;JOD'SFF
PowderMet 2010 – Booth 400 www.nah.com
FRONT MATTER_ FRONT MATTER 4/27/2010 2:26 PM Page 4
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AMETEK
AMETEK
AMETEK’s
AMETEK
WWWAMETEKMETALSCOM
Visit Visit us at BOOTH # 301
CONSULTANTS' CORNER_ CONSULTANTS' CORNER 4/27/2010 2:27 PM Page 5
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CONSULTANTS’ CORNER
DAVID WHITTAKER* Q A
How important a role have developments in pressing lubricants played in enhancing PM products? For many years, manufacturers of PM parts had a love–hate relationship with admixed pressing lubricants. The benefits of lubricants in the compaction stage are well recognized in the vital protection of: the forming tooling against damage; the reductions in forming and ejection pressures and, in part, green-density variations arising from reduced levels of friction between the “workpiece” material and the tooling surfaces; and the contribution to enhancing surface finish in the formed green part. However, personnel involved in operating a sintering furnace will often have wished that the lubricant was never there in the first place, as removing it effectively from the part prior to sintering might arguably cause them more problems than any other factor. Over the years, these problems have been a major source of the stimulus for efforts to develop viable diewall-lubrication technology. Die-wall-lubrication systems are now utilized in production, but are not a complete substitute for the use of an admixed lubricant since, except for simple product shapes, some of the relevant tooling element surfaces are not accessible for direct lubrication at the fill stage. Also, admixing of lubricant is a foolproof system, as long as one remembers to make the addition. A diewall-lubrication system has only to fail once to deliver the lubricant and the tooling is damaged. Thus it seems inevitable that admixing of pressing lubricant is bound to remain with us as a mainstay of PM technology. Given this scenario, the need to include an admixed lubricant has, in fact, been turned to impressive advantage by the major powder suppliers over the last two decades. Indeed, a strong argument can be mounted that developments in this technology have enhanced PM part capabilities as much as any
other advances. Whatever other competitive advantages PM can claim to offer, the ability to accurately control final part dimensions, and consequently eliminate the need for many machining operations, is where it all starts. It has been the use of bonded premixes, based on the development of binder-lubricant systems, that has made a major impact on this issue. Although diffusion alloying can be an effective means of eliminating the segregation of certain alloying elements in a powder mix, other additions such as graphite and lubricant cannot be attached to the base-iron powder particles by diffusion alloying. Also, these additions are low-density materials prone to dusting in powder handling and in die fill. Bonded premixes, in which such additions are held in place using an “adhesive” binder, were first introduced in the late 1980s and delivered, as expected, reduced dusting and a decreased tendency for segregation. As a result, improved consistency of sintering response and dimensional control was achieved and more consistent powder-flow characteristics were also derived. However, the original generation of bonded premixes was seen as sacrificing some degree of compressibility in exchange for these benefits. This was because the binder content added to that of the normal pressing lubricant and therefore the total organic content (and volume fraction occupied by the organic constituents in the pressed part) increased. This limitation was overcome in the second generation of bonded premixes, in which alternative organic material additions were made that were capable of acting both as a binder and a lubricant. Grades are now available in which all alloying additions are bonded to the base iron, as an alternative to diffusion alloying. These grades can show benefits over their diffusion-alloyed counterparts in terms
*Consultant, David Whittaker & Associates, 231 Coalway Road, Merryhill, Wolverhampton WV3 7NG, UK; Phone: 44 1902 338498; E-mail:
[email protected]
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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CONSULTANTS’ CORNER
of higher apparent density and improved flow characteristics. The second area where lubricant developments have made an important contribution to pressing has been in deriving higher green-density levels, and ultimately higher as-sintered strength levels, in pressedand-sintered parts. Whatever compaction technology is employed, one factor that limits maximum achievable green density is the volume fraction occupied by the relatively low-density pressing lubricant (and the graphite addition made to many ferrous powder mixes). A number of developments have appeared in recent years that have focused on reducing the required levels of admixed lubricant. Some of these developments have been particularly relevant to the introduction of warm-die compaction, as a variant on the original warm-compaction process. Hoeganaes Corporation’s introduction of this process has been based on the use of a new binderlubricant, AncorMax®200. The use of this binderlubricant allows parts to be pressed to green density levels up to 7.4 g/cm3, without heating the powder and with the tooling heated to ~93°C (200°F). This tooling temperature is marginally above the level reached by frictional heating during conventional cold compaction, but the superior control over tooling temperature through thermostatic heating contributes to the observed significant benefit in part-weight consistency. The key to the higher density response is that this system employs specialized lubricants that allow a lower total amount of lubricant than in conventional systems (0.40 w/o). Because of this reduced lubricant content, however, the system is currently recommended only for part lengths <32 mm. More recent lubricant developments have allowed warmdie-compaction tooling temperatures to be extended to 110°C and warm-compaction process temperatures to be increased to 175°C. North American Höganäs has also reported on a new lubricant, Intralube®, that can be used at lower addition levels in combination with elevated die temperatures.
Q A
How have recent developments in the Global PM Property Database (GPMPD) enhanced the support for fatigue design of PM components? The design of “real” components always involves the consideration of the effects of stress-raising notches. Also, most applications involve fatigue-loading modes other than fully reversed loading (R = -1). To apply local stress or strain-fatigue-design concepts, fatigue curves derived with notched test pieces
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(Kt values >1) and with R at values other than –1, must be available. On the basis that the primary PM targets in morehighly stressed applications (e.g., automotive engines and transmissions) are not likely to experience macroscopic plasticity in service, local-stress concepts can be applied and designers are content to rely on load-controlled S-N data in their design methodologies for such applications. Prior to the advent of the GPMPD, the most likely collated sources of fatigue information on PM materials were the typical values given in standards such as MPIF Standard 35 and ISO 5755. This information fell short of what designers needed in two respects: • The data related only to unnotched test pieces (Kt = 1) and fully reversed loading conditions (R = 1). Indeed, most of the fatigue data presented in the standards are based on rotating bend testing, necessarily at R = -1 and Kt = 1. • Only fatigue-endurance limits were quoted, rather than displaying full fatigue curves. Initially, the fatigue data in the GPMPD could be criticized on similar grounds, as the basic search options offered access only to fatigue-endurance limit values, determined at R = -1 and Kt = 1. However, the latest extension of capability, introduced in 2009, has involved making full S-N fatiguecurve pages (comprising S-N curves and details of individual test points) accessible to searchers. The initial content comprises over 130 S-N curve pages, covering a range of iron–copper–carbon grades, on the basis that they constitute at least half of the current PM structural-parts market. In addition, their fatigue properties have already received significant attention in published research. This published information has been analyzed and collated by the group led by Professor Paul Beiss, Technical University of Aachen. The collated S-N curves cover a range of material-processing conditions and density levels and a range of fatigue-testing conditions (fatigue-loading mode, mean stress level, and notch factor). A further shortcut button has been added to the menu on the opening page of the GPMPD Web site which allows access to a tabulation of all S-N fatigue curves in the database. From this tabulation, the searcher can select a link for any material/condition of interest, which displays the relevant S-N curve as a pdf file that can be viewed online or downloaded. Links also exist from relevant grade report pages, which access tabulations restricted to S-N curve pages for the particular grade only. As a supplement to these S-N fatigue curves, a number of endurance-limit values have been added to Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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CONSULTANTS’ CORNER
the database, to cover a range of material grades and density levels plus a range of fatigue-testing conditions. The values for R other than –1 and Kt other than 1 can be accessed using the “Advanced Search” facility and by entering the relevant values of axial or plane bend R and Kt on the property-selection page. To access this enhanced fatigue information, take another look at the GPMPD. If you have not previously used the database, register at www.pmdatabase .com—it is free of charge.
Q A
Are CCT (Continuous Cooling Transformation) diagrams available for PM materials? CCT diagrams for some PM material grades are available, although during my research on this question I came to the conclusion that there is no single, collated source of this type of information—unless Google or I have missed it! In light of the growing interest in sinter hardening and the development of new grades tailored to the use of this technology by the major powder suppliers, I felt sure that the derivation of CCT information would have been relevant to these efforts. So, I started my search on the Web sites of these powder suppliers. Generally, it was possible to go from the home pages of these sites to a technical paper library page.
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
In most cases, by using a keyword search, it was then possible to access copies of relevant papers presented at recent international conferences and, hence, the CCT information. In some cases, the powder suppliers present information directly in the form of the CCT diagrams. In other cases, information is available as plots of percentages of the various transformation products in the final microstructure as a function of the pre-transformation cooling rate. For the PM practitioner, such plots are probably more useful than the original CCT diagrams. Given the apparent absence of an independent, collated source of this CCT information, perhaps this could be a future project for the GPMPD.
Q A
What is the expected trend for new or expanding PM parts-fabrication plants in Asia? Although my crystal ball is not good enough to give a fully quantified answer to this question, there are many indicators that the forthcoming expansion of PM capacity in Asia will be strong. The general rule with PM technology is that an analysis of trends in the automotive sector is always a good starting point for assessing future demand. In his excellent global market review (International Powder Metallurgy Directory, 2010–2011 Edition),
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Bernard Williams has reported an increasing shift in automotive production to non-OECD (Organization for Economic Co-operation and Development) countries in recent years. This trend also exists in other regions such as Latin America and Eastern and Central Europe, but it is particularly strong in the rapidly growing economies in Asia. OECD information indicates that, between 2000 and 2007, the share of the non-OECD areas in global vehicle production increased from 1 in 10 to 1 in 5. While the distorting effects of the “credit crunch” make analysis of production figures for the past couple of years problematic, it is clear that the emerging economies in Asia have continued that strong growth in vehicle production levels, in contrast to the situation in the OECD countries. The largest of the growing Asian economies, China, produced 9.345 million vehicles in 2008 and it is likely that China will have overtaken the U.S. as the largest automotive market in the world with sales of over 13 million in 2009. India, the only competitor to China in terms of economic growth potential (forecast by the World Bank to show real GDP growth in 2011 of 8.5%), has already grown its vehicle production by over 40% to over 2.3 million in the period from 2005 to 2008. China’s PM sector, in particular, currently has a low automotive part dependence (~55% in 2008) compared with the OECD regions. However, this automotive dependence would be expected to grow in parallel with the growth of the country’s vehicle production. It seems likely that established PM operations and new entrants to the technology, in both China and India, will be particularly keen to base this growth in automotive business on acquiring the ability to produce those parts currently seen as high-value applications. So, the one piece of good news for North American and European PM companies active in such applications is that there may be interesting jointventure opportunities to be pursued. ijpm Readers are invited to send in questions for future issues. Submit your questions to: Consultants’ Corner, APMI International, 105 College Road East, Princeton, NJ 085406692; Fax (609) 987-8523; E-mail:
[email protected]
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Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Peter Johnson_Zheng et al 4/27/2010 2:29 PM Page 9
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ANNUAL TECHNOLOGY REVIEW
PM’S NEW GROWTH ENGINE—TECHNOLOGY DEVELOPMENT Peter K. Johnson*
The MPIF Technical Board, chaired by Russell A. Chernenkoff, senior project engineer, Metaldyne LLC, is assessing technology issues that affect PM’s future growth. These include single-press-to-full-density, an update on metal injection molding (MIM) trends, and an evaluation of the potential threat of competitive and disruptive technologies. The last cover processes such as forging, stamping, and casting. Hybrid and electric vehicles represent another disruptive technology that could reduce the number of PM applications in vehicles. At the same time they present opportunities for PM, especially for parts made from new materials. The Technical Board is also studying potential PM applications in renewable energy. The Center for PM Technology (CPMT) is working on several issues to move PM technology forward, says William F. Jandeska Jr., program manager. Supported by almost 40 companies, CPMT’s programs are aimed at generating a path to higher density via new tooling concepts and higher-tonnage presses capable of compacting pressures >828 MPa (60 tsi). “We are investigating more-robust tooling materials and construction, and new lubrication advances,” Jandeska says. “CPMT’s programs have achieved single-press final densities >7.45 g/cm3 on complex parts.” CPMT is also developing data for establishing machinability guidelines and life-cycle fatigue data.
While the “new normal” in the North American automotive-parts supplier market may be levelling powder metallurgy’s (PM) growth curve, there are still developments that could open up new opportunities. Based on input from member companies of the Metal Powder Industries Federation (MPIF), metal powder producers, equipment suppliers, and PM parts makers are busy investing in new materials, processes, and technology. This review assesses developments and trends in each of these sectors of the PM industry. Never write off the creative resiliency of PM companies to overcome obstacles.
METAL POWDER ADVANCES Metal powder makers are studying new materials and processes to extend PM’s dynamic properties and competitiveness. “The economic downturn has had an impact on PM to the same extent as it had on competing technologies,” says Sim Narasimhan, FAPMI, vice president, chief technology officer, Hoeganaes Corp., Cinnaminson, New Jersey. “PM continues to be an economic alternate to forging, stamping, castings, and machined parts.” The company offers new products that improve PM’s competitiveness. For example, Ancorsteel® AMH is an atomized powder with a sponge morphology, excellent green strength, and green density, targeted to replace iron-ore reduced sponge iron, Figure 1. Utilizing a heated die and powder, Ancordense® 450 can achieve densities up to 7.55 g/cm3. Seeking to lower alloy content, Hoeganaes has introduced Ancorsteel *Contributing Editor, International Journal of Powder Metallurgy, APMI International, 105 College Road East, Princeton, New Jersey 08501-6692, USA; E-mail:
[email protected].
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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Peter Johnson_Zheng et al 4/27/2010 2:29 PM Page 10
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PM’S NEW GROWTH ENGINE—TECHNOLOGY DEVELOPMENT
Figure 1. Ancorsteel AMH atomized powder with spongy morphology
721SH for sinter hardening and Ancorsteel 30HP for applications requiring heat treatment. North American Höganäs Inc. (NAH), Hollsopple, Pennsylvania, is also concentrating on cost-effective alloys for heat treating and sinter hardening, reports Ian Howe, director of application development. The company has introduced two new alloys that are aimed at highly loaded fatigue applications that are conventionally heat treated. Astaloy CMN provides cost effectiveness and fatigue performance at a density of 7.20 g/cm3 relative to competing materials, Figure 2. D.AQ, a lean diffusion-bonded alloy for conventionally heat-treated parts, is a cost-effective alternative to traditional alloys with higher nickel and molybdenum contents. NAH reports that lean chromium alloys continue to make strides in new high-performance applications because of a combination of cost savings,
Figure 2. Cost–fatigue performance positioning of Astaloy CMN Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
hardness, fatigue properties, and impact resistance. Astaloy CrL, warm compacted and sinter hardened at a high temperature to a density of 7.40 g/cm3, is opening up new demanding applications such as non-automotive transmission gears. It has an HRC 35 hardness, 1,200 MPa (174,000 psi) tensile strength, and an impact strength >40J (>29.5 ft.·lb.). Rio Tinto Metal Powders (QMP), Sorel-Tracy, Quebec, Canada, is focusing its R&D efforts on developing alternative molybdenum, nickel, and copper materials at a lower cost than diffusionbonded powders, reports François Chagnon, principal scientist. The company offers customized organic bonded materials with nickel–molybdenum–copper that optimize chemistry and physical properties to meet specific customer requirements with minimal sensitivity to alloy-price volatility. In addition, Rio Tinto engineers have developed ATOMET 22, a new low-apparent-density powder with improved green strength for low-density applications. Deepak Madan, vice president of technology and new product development, reports that Magnesium Elektron Powders, Manchester, New Jersey, has upgraded the magnesium powder atomizer at its Hart Metals plant in Tamaqua, Pennsylvania. The new upgrades include an energy-efficient furnace, an automated ingot feeding and pre-heating system, and an automated powder handling, screening, and recovery system. The company received a $1.6 million grant from the U.S. Department of Defense to develop new highperformance magnesium alloy powders and composites. Its R&D team is working with the U.S. Army Research Laboratory, Aberdeen Proving Grounds, Maryland, to develop magnesium alloys and composites for manufacturing lightweight parts for weapons systems. New powders and applications offer favorable growth prospects for the copper powder industry. American Chemet Corporation, Deerfield, Illinois, is developing enhanced-performance copper powder and alloys for iron powder additions to reduce or improve dimensional change, says William H. Shropshire, PMT, market development manager. The company is also expanding products in the single-digit micron range. Pierre W. Taubenblat, FAPMI, president of Promet Associates, Highland Park, New Jersey, sees renewed interest in electrolytic copper powder that provides high green strengths up to 69 MPa
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PM’S NEW GROWTH ENGINE—TECHNOLOGY DEVELOPMENT
(10,000 psi). He also sees new opportunities for copper powders in friction products, plastics, greases, biomedical products, foams, welding, plumbing fixtures, and thermal management. For example, copper–tungsten and copper–molybdenum powders are finding increasing application in heat sinks. Another thermal management product use is dispersion-strengthened copper containing insoluble dispersoids that provides unique properties such as stress retention at higher temperatures. Aluminum powder is also on the move, according to Clive Ramsey, president of United States Metal Powders Inc., Flemington, New Jersey, whose subsidiary Ampal, Inc., is a major supplier of the lightweight metal. Ampal will introduce AMB 2800, a new aluminum PM grade providing almost zero shrinkage, minimal part-to-part dimensional variation and good mechanical properties under standard production conditions. The company expects to release a new high-performance series of PM aluminum grades for automotive engine parts that feature excellent mechanical properties. In addition, Ramsey sees demand for aluminum powders increasing in the solar power and electronics markets. Environmentally friendly rocket propellants consisting of aluminum powder and water ice are another innovative use. PM EQUIPMENT TRENDS PM equipment suppliers are pushing the technology envelope. Dorst America, Inc., Bethlehem, Pennsylvania, is working with key players in the industry to raise the capability of the PM process to the next level, reports Gregory D. Wallis, CEO. Dorst is introducing a 100-percent electronically controlled EP series press that provides precision that is equal to or higher than CNC hydraulic models. According to Wallis, the new press will play a significant role in the PM market from 5.4 to 109 mt (6 to 120 st) pressing capability with high output rates and low energy usage. Erowa Technology, Inc., Arlington Heights, Illinois, offers a rapid-tooling-change system (Figure 3) that reduces compacting press set-up times to minutes instead of hours, says Chris Norman, vice president, engineering/technology support. PM tooling pallets and die-plate and punch chucks allow much quicker changes from part to part, the company claims, in addition to position repeatability within two microns. Elnik Systems, Cedar Grove, New Jersey, a sup-
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Figure 3. Rapid-tooling-change system (PM tooling pallet)
plier of metal injection molding (MIM) debinding and sintering furnaces, is focusing on automation, closer temperature tolerances, and the development of new process parameters to reduce processing time in batch furnaces, reports Dori Leonard, marketing department. The company has upgraded its furnace debinder trap and muffler to include automatic cleaning, Figure 4. An automatic flushing system in the vacuum pump permits easier furnace maintenance. Elnik’s affiliate, DSH Technologies, has conducted trial runs in the company’s furnaces to shorten debinding and sintering times. Sunrock Ceramics Co., Broadview, Illinois, is developing new high-temperature alumina ceramics for the PM industry (Figure 5), reports Doug Thurman president. The company has recently introduced HPA-99, a 99.5 percent alumina refractory for hot-face linings and hearths in pusher furnaces. This new product complements the HPACG pusher-plate material for high-temperature furnaces and the finer-grain HPA for setter tiles. TempTabs is a new product offered by The Orton
Figure 4. Muffler and debind-trap cleaning system Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Peter Johnson_Zheng et al 4/27/2010 2:30 PM Page 13
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PM’S NEW GROWTH ENGINE—TECHNOLOGY DEVELOPMENT
Ceramic Foundation, Westerville, Ohio, that monitors and records the effect of temperature and time-at-temperature inside batch and continuous furnaces (Figure 6), reports Jim Litzinger, director business development. The product is made from a blend of materials that exhibit predictable dimensional change over a relatively wide temperature range of 200°C–300°C (392°F–572°F). The product can be used for atmosphere and vacuum furnaces. After firing, TempTabs are measured to the nearest 0.01 mm. The final dimension can be input into Orton’s TempTrak software program where it is converted to a TempTab temperature and graphically displayed. By establishing a scheduled interval furnace monitoring run, companies can determine the natural variation of furnaces and spot temperature trends before they can adversely affect products. Arburg GmbH + Co KG, Lossburg, Germany,
Figure 5. High-performance ceramic refractory parts
Figure 6. TempTab temperature-monitoring system Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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Peter Johnson_Zheng et al 4/27/2010 2:30 PM Page 14
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PM’S NEW GROWTH ENGINE—TECHNOLOGY DEVELOPMENT
Figure 7. PIM feedstock testing system
offers their cost-effective Selogica machine-based powder injection molding (PIM) feedstock testing system (Figure 7), reports Uwe Haupt, sales representative. Prior to production runs, a batch test indicates whether parameter changes must be made for a material batch, which allows production to proceed more smoothly. Collecting and comparing the data over a prolonged time provide information about determining acceptable batch fluctuation ranges without the need for PIM parameter changes. New injection parameters can be designed for batches outside of this range. The Selogica system saves time and eliminates expensive rejects, the company claims. Marketing its high-density crowned gear technology, Capstan Atlantic, Wrentham, Massachusetts, is gaining new business opportunities and a gear-endurance performance edge, says Richard H. Slattery, vice president, engineering. Crowned gears significantly improve the load distribution on gear teeth by eliminating potential “point loading” and reducing noise. Gear crowning is performed as a secondary operation on as-sintered preforms. Field tests on single-pressed, highdensity crowned carburized gears have shown a 100 percent increase in contact fatigue endurance over conventionally manufactured heat-treated PM gears. This is due to the influence of the crown on contact-stress distribution, Figure 8. The company is focusing on stabilizing part distortion through heat treatment to provide more precise gears. Its current technology produces gears at AGMA Q8/9 precision levels. HIGH-DENSITY PM PARTS & PRODUCTS PMG Corporation, Columbus, Indiana, sees the next growth trend in PM automotive applications
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Figure 8. Contact-stress distribution with a crown
coming from increased demand for cost-effective parts and systems in engines and transmissions that improve fuel economy, reports Salvator Nigarura, research & development manager. The company’s DensiForm® proprietary technology improves wear resistance and provides closer tolerances for complex vane-type actuators in engines. It can also replace higher-cost materials with lower-cost ones while achieving similar or higher levels of wear resistance. PMG is making dual-clutch transmission synchronizer hubs and rings as well as clutch cones and sliding sleeves. To increase the market share of synchronizer rings, the company offers a complete synchronizer ring system, Figure 9. During the past five years it has also replaced forged roller one-way clutches with DensiForm® PM parts. New near-net PM applications in oil and gas exploration and land-based turbines are growth markets for the hot isostatic pressing (HIP) business, reports Dennis Poor, president of Kittyhawk Products, Garden Grove, California. Demand for
Figure 9. Dual-cone ring system: PM outer, inner, and intermediate rings Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Peter Johnson_Zheng et al 4/27/2010 2:30 PM Page 15
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PM’S NEW GROWTH ENGINE—TECHNOLOGY DEVELOPMENT
HIPed PM tool steels, titanium, and more-exotic alloys are growing as well. Diffusion bonding for nuclear-energy applications is another growth market. For example, pilot projects involve diffusion bonding of the first wall of a reactor. The densification of MIM parts is still another growing HIP market. There is increased demand for large stainless steel and superalloy near-net-shape products, says Greg Del Corso, manager, Powder Products R&D, Carpenter Powder Products, Reading, Pennsylvania. Additional trends include improved free-machining tool steel and stainless steel bar and wire made from HIPed gas-atomized powder,
and powders for additive manufacturing operations such as laser claddi ng and direct laser sintering. The advantage of energy-efficient and environmentally friendly PM technology is proving itself as a major factor contributing to future cost reduction, particularly in relation to expensive materials like titanium, reports Stanley Abkowitz, CEO, Dynamet Technology, Inc., Burlington, Massachusetts. The introduction and application of new titanium-base components will benefit by recent advances in near-net-shape and mill-product manufacturing developed by the company. ijpm
This is how a Revolution looks nowadays: Compact. Economic. Quiet.
A revolutionary drive concept makes it possible: The new CA-SP 160 Electric features a minimal power consumption. Further advantages are the low noise level and a floor space requirement reduced by three quarters compared to a conventional press. OSTERWALDER AG CH-3250 Lyss/Switzerland Phone +41 32 387 14 00
OSTERWALDER Inc. Cincinnati, Ohio 45242/USA Phone +1 513 936 90 06
OSTERWALDER (Shanghai) Technology Co., Ltd. · Shanghai 200032/China Phone +86 21 64 17 84 26
www.osterwalder.com
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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Peter Johnson_Zheng et al 4/27/2010 2:31 PM Page 16
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EXHIBITOR SHOWCASE 2010_ EXHIBITOR SHOWCASE 2009 4/27/2010 2:41 PM Page 17
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Exhibitor Showcase
Experts from leading PM and particulate materials companies will answer questions about the latest trends in powders, production equipment, process technologies, testing, and QC equipment and products. The exhibition features process equipment and provides a valuable opportunity to meet with current or new suppliers. Receive immediate help with production and materials questions. Arrange appointments now with the companies you want to visit and arrive with your list of technical issues for one-on-one discussions. Take advantage of this valuable opportunity to gain new information from major suppliers and network with industry technical leaders.
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EXHIBITOR SHOWCASE 2010_ EXHIBITOR SHOWCASE 2009 4/27/2010 2:42 PM Page 19
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Exhibitors ABBOTT FURNACE COMPANY St. Marys, PA Abbott specializes in continuous furnaces for sintering, steam treating, quenching, annealing, tempering, and brazing. Silicon Carbide muffles, a Quality Delube Processor, and VariCool are all popular options. Pusher furnaces and ceramic belt models are suitable for higher-temperature applications. Spare parts, fabrications, repairs, and calibrations are offered. ISO/IEC 17025 Accredited. ABTEX CORPORATION Dresden, NY Abtex Corporation manufactures application specific, abrasive filament deburring brushes and automated brush deburring systems. Our latest compact system, a Tri-Ten return-to-operator machine, provides double side deburring of PM parts, includes two highly automated machines developed for a Japanese Auto Supplier. Machine and brush designs for both “green” and sintered parts. AC COMPACTING LLC North Brunswick, NJ AC Compacting LLC carries a line of small and large parts weight sorters, sorting by weight pieces from 50 mg to 30 grams or more, with accuracies to +/- 1 mg. AC also carries industrial rotary presses with 60 ton and 4 inch capacities. ACUPOWDER INTERNATIONAL, LLC. Union, NJ/Greenback TN ACuPowder, with plants in NJ & TN, is a major U.S. producer of metal powders. Products include: Antimony, Bismuth, Brass, Bronze, Bronze Premixes, Copper, Copper Alloys, Copper Oxide, Copper Premixes, Diluted Bronze Premixes, Graphite, High Strength Bronze, Cu Infiltrant, Manganese, MnS+, Nickel, Phos Copper, Silicon, Silver, Tin, Tin Alloys and PM Lubricants. New products include powders for MIM, Thermal Management, "Green" Bullets, Lead Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Free Solders, Plastic Fillers, Cold Casting and most recently Ultra Fine/Ultra Pure Copper Powders for the electronics industry. AMERICAN CHEMET CORPORATION East Helena, MT & Deerfield, IL American Chemet, est. in 1946, manufactures copper powders, dispersion strengthened Cu, and copper and zinc oxides. Chemet’s oxide reduction process allows a high degree of control over particle size and shape in powders ranging from molding grade (150 mesh) to 12 micron median size. AMETEK, INC. Eighty Four, PA Ametek and Reading Alloys produce specialty powders primarily for aerospace, automotive, electronic, hardware and medical industries. Products include Ultra 300 and 400 series stainless powders for PM, MIM, and filter markets, nickel-base thermal spray powders and specialty alloys such as titanium CP and Ti 6/4 powders. Ametek/ Reading Alloys is a world leader in research, development and manufacture of high-grade aerospace master alloys, specialty metals, and coatings materials. AP&C ADVANCED POWDERS & COATINGS Boisbriand, Canada AP&C produces the world’s most spherical metallic powders. AP&C plasma technology can atomize most metals such as titanium, titanium alloys, niobium, zirconium, molybdenum and countless more. AP&C quality powders are ideal for metal injection molding, hot isostatic pressing, laser deposition, rapid manufacturing and most coating applications. The product offers excellent flow ability, few contaminants and a low oxygen levels. For more details regarding these and other AP&C quality products please contact Mr. Bruno Beauchamp by dialing 450.434.1004 256 or via e-mail at
[email protected]
APMI INTERNATIONAL Princeton, NJ APMI International is the professional society for individuals involved in powder metallurgy and particulate materials. Members include metallurgists, engineers, teachers, students and business people. Some of the many benefits include: International Journal of Powder Metallurgy, Who's Who in PM membership directory, full access to PM NEWSBYTES and monthly PM Industry NewsLine. Stop by our booth and learn how APMI can be your professional resource. ASBURY-SOUTHWESTERN GRAPHITE Asbury, NJ For over 100 years the worldwide leader in graphites and carbons for the Powder Metal industry. Our complete line of natural and synthetic graphites for conventional PM applications, specialty materials for forging, bearing, and hard metal applications will be presented. Asbury also supplies a complete line of graphite sintering trays and parts as well as graphite , Moly and other metal working lubricants. Metal sulphides and metal alloy powders are also available from Asbury. AUTOMATED CELLS & EQUIPMENT Painted Post, NY The Spiders Are Coming! ACE will demonstrate vision guided braze pin assembly using a new FANUC robot. ACE is promoting these innovative robots for high speed assembly and material handling. The spider robots are available in two sizes with either a 4 or 6-axis wrist. See the Powder Metal automation experts at booth #521. BASF CORPORATION Evans City, PA Catamold is BASF's ready-to-mold feedstock for MIM and CIM, we offer a diverse portfolio of low-alloy steels, stainless steels, special alloys and ceramics. BASF supports customers with material development, training
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EXHIBITOR SHOWCASE 2010_ EXHIBITOR SHOWCASE 2009 4/27/2010 2:42 PM Page 20
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Exhibitors and technical support based on our extensive experience as the world’s leading feedstock supplier. Contact BASF: 724-538-1378, or at www.basf.com/catamold. BRONSON & BRATTON, INC. Burr Ridge, IL Bronson & Bratton, Inc. has been in the Tool & Die business since 1948, and has been building PM Tooling since 1970. We have the Design (CAD), Manufacturing (CAM), and the experience to design and build the Tooling/ Adapters required to fit your existing Compacting/Sizing Presses. We are ISO 9001:2000 certified. C.I. HAYES INC. A SUBSIDIARY OF GASBARRE PRODUCTS, INC. Cranston, RI Manufacturers of custom-designed sintering and heat-treating furnaces with temperatures to 3,000°F. Hayes' atmosphere furnace designs include, belt, pusher, walking beam. Vacuum furnaces in batch or continuous and feature isolated heating and quenching chambers. Continuous vacuum carburizing. Endothermic, exothermic, and DA generators. Full line of replacement parts. CARPENTER POWDER PRODUCTS INC. Bridgeville, PA Provides prealloyed powders that are tailored to meet customer requirements for thermal surfacing processes, metal injection molding, near net shape hot consolidation technologies, and mill form products (billet, bar, wire, plate, sheet, and strip). Our manufacturing versatility and technical knowledge enable us to provide you with consistent high quality products. CENTER FOR POWDER METALLURGY TECHNOLOGY (CPMT) Princeton, NJ Celebrating its 30th year, the Center for Powder Metallurgy Technology
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(CPMT) is a not-for-profit foundation established by members from the PM community. CPMT funds cooperative technology programs focusing on R&D that bring together the corporate, academic, and research organizations to advance PM technology. Center members benefit from periodic research reports and guide the direction of research activities. Other activities include scholarships and grants provided to industry students.
cold isostatic presses (CIP) and hot isostatic presses (HIP) with large production facilities in North America and Europe. The company offers state-ofthe-art isostatic production lines as turn-key solution for the PM and Ceramics industry as well as know-how and customer service for the operation of these lines. Dieffenbacher is ISO 9001 certified with specialised staff in enginering, design, controls and manufacturing.
CENTORR/VACUUM INDUSTRIES, INC. Nashua, NH High-performance Metal Injection Molding Furnaces for alloy steels, stainless steel, tool steel, hardmetals and ceramics. Laboratory to production size. Temperatures to 2,300°C in vacuum, inert, or hydrogen gas from 10–750 torr. Graphite or refractory metal hot zones with proprietary Sweepgas binder removal systems for injection molded parts.
DORST AMERICA, INC. Bethlehem, PA Continuous innovation, leading technology and outstanding customer service have made Dorst the market leader for CNC Electric and Hydraulic presses in the PM and related industries. Our all-encompassing approach, ranging from products to technological support and after-sales service, enables customers to optimize the most demanding jobs and perform with exceptional capability and productivity.
CINCINNATI INCORPORATED Cincinnati, OH CINCINNATI INCORPORATED manufactures PM Compacting and Restrike Presses. All presses are backed by extensive support services, including reconditioning and upgrading existing equipment to ensure maximum performance and productivity. Video and photographs will be shown highlighting various products and services available.
ELMCO ENGINEERING INC. Indianapolis, IN ELMCO Engineering Inc. is a leading manufacturer of new and rebuilt PM equipment of all makes and sizes. We service all makes of presses, and have an extensive parts inventory. We are North American Representatives for Yoshizuka presses. ELMCO also offers custom engineering for special applications. Visit us in Booth #301.
CM FURNACES, INC. Bloomfield, NJ Fully automated high-temperature continuous pusher furnaces for both traditional powder metal and metal injection molding with inline debinding. These furnaces operate in a hydrogen/ nitrogen atmosphere up to 3,100°F with extremely low dew points. Also being displayed will be our line of high-temperature hydrogen batch furnaces.
ELNIK SYSTEMS/DSH TECHNOLOGIES Cedar Grove, NJ ELNIK SYSTEMS provides Solvent/ Catalytic debinding and ONE-Step Debind and Sinter furnaces for metal injection molded parts. Both systems utilize integrated loading trays which reduces handling and saves times. DSH Technologies, LLC, your partner in MIM, offers trials runs, consulting and R&D, and set up of turn-key project MIM operations.
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DIEFFENBACHER GMBH & CO. KG Eppingen, Germany Dieffenbacher is a major supplier of
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
EXHIBITOR SHOWCASE 2010_ EXHIBITOR SHOWCASE 2009 4/27/2010 2:42 PM Page 21
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ERASTEEL DIVISION OF ERAMET Boonton (NJ) and Chicago/Romeoville (IL) Erasteel: Your flexible powder source With atomization units based in Sweden and 40 years of experience, Erasteel is the world leading producer of highquality gas-atomized metal powders for tooling and components. Alloy types include high-speed steels, tool steels, stainless steels and other alloys. Contact us at
[email protected] EROWA TECHNOLOGY, INC. Arlington Heights, IL “Pulverizing Set Up Times”—EROWA Technology (Arlington Heights, IL) is the world leader in palletization and automation solutions for the manufacturing industry. EROWA’S PM Tooling System palletizes the punches as well as the die/mold; enabling press resetting
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in less than 3 minutes. The 0.002 mm repeatability eliminates punch damage during press set-up. See us at the PowderMet2010 show in booth #404! EUROPEAN POWDER METALLURGY ASSOCIATION Shrewsbury, England In 2010 the European Powder Metallurgy Association (EPMA) will be organising the World PM2010 Congress & Exhibition, 10-14 October 2010, at the Fortezza da Basso Congress Centre, Florence, Italy. This prestigious event will be an international showcase for Powder Metallurgy and associated sectors. Further event information is available at www.epma.com/pm2010 GASBARRE PRESS DIVISION GASBARRE PRODUCTS, INC. DuBois, PA Designers and manufacturers of single-
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level and multi-level Mechanical and CNC Hydraulic Presses—5 to 1,200 Tons for compacting and sizing of structural PM parts. Removable die set presses are available. TOPS Powder Heating Systems, Die Wall Lubrication Units, Fluidized Filler Shoes, Parts Automation, and Powder Handling Systems. Extensive rebuild services and press replacement parts inventory. GEM HI-TECH CO., LTD Shenzhen, China GEM—CHINESE SPECIALIST IN COBALT & NICKEL POWDER GEM (Green Eco-Manufacture) headquartered in Shenzhen, China, founded in 2002 and successfully to be A-shares listed company in Shenzhen on 22nd January, 2010. TEL:(86)755 33386666 FAX:(86) 755 33895777
HOT ISOSTATIC PROCESSING SERVICES FOR PRODUCTION AND RESEARCH PROGRAMS ISO 9001, AS9100 REGISTERED
• CASTING DENSIFICATION • Improved Properties • Reduced Rejection Rate • Reduced Scrape Rate
• POWDER CONSOLIDATION • PRESSURE BRAZING • DIFFUSION BONDING • CERAMICS
KITTYHAWK PRODUCTS
11651 MONARCH ST. • GARDEN GROVE, CA 92841 Tel. (714) 895-5024 Fax (714) 893-8709 www.kittyhawkinc.com E-mail:
[email protected]
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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EXHIBITOR SHOWCASE 2010_ EXHIBITOR SHOWCASE 2009 4/27/2010 2:42 PM Page 22
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Exhibitors GLOBAL TUNGSTEN & POWDERS CORP. Towanda, PA Global Tungsten & Powders Corp. (GTP) located in Towanda, Pennsylvania, and GTP BRUNTAL, located in Bruntal, Czech Republic, combine to create a world leader in the production of APT, tungsten, tungsten carbide, molybdenum, cobalt, and tantalum powder products. GTP features its tungsten carbide powders, POWDER PERFECT thermal spray powders, and offers a diverse selection of tungsten powders. We service the hard materials, energy, automotive, defense, electronics, medical, and aerospace markets.
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GRIPM ADVANCED MATERIALS CO., LTD Beijing, China Largest producer of nonferrous copper
and copper alloy powder in China, annual capacity over 10000 MT, products include electrolytic copper powder, atomized copper and copper alloy powder, cobalt powder, tin powder, thermal spraying wires and powder etc. with professional solution services used in PM, diamond tools, carbon brushes, friction materials, surface engineering etc. applications. HOEGANAES CORPORATION Cinnaminson, NJ Hoeganaes Corporation, world leader in ferrous powder production, has been a driving force within the PM industry’s growth for over 50 years. It has seven manufacturing facilities in the United States, Europe and Asia to meet customers’ needs worldwide. It holds these certifications: ISO 14001, ISO/TS 16949, and QS 9000.
HORSEHEAD CORPORATION Palmerton, PA Horsehead Corporation is a major supplier of zinc and brass powders as well as copper, bronze, infiltrants, phos-copper, and nickel silver powders. Horsehead, formerly New Jersey Zinc Co., makes air-atomized powders at its plant in Palmerton, Pa. This facility has been supplying the PM industry with nonferrous powders for more than half a century. For information contact
[email protected] INDUSTRIAL HEATING MAGAZINE Pittsburgh, PA The metal-powder industry's only fully audited monthly trade journal for metal-powder engineers, part designers, applications engineers, equipment manufacturers, powder producers and suppliers."
Pioneer of Induction o Plasma Materials
Plasma Treated T Powders e for High Performance r Components m Specializing in refractory metals, advanced a ceramics and alternative t materials:
s 3PHERICAL AND 0LASMA $ENSIFIED 0OWDERS A N W s .ANOPOWDERS Z M s #USTOMIZED 0OWDER 4REATMENT 3ERVICES s 0RODUCT $EVELOPMENT $
For more information: +1 819.820.2204 www.tekna.com
[email protected] TEKNA ADVANCED MATERIALS INC. 2895 INDUSTRIAL BLVD SHERBROOKE QC J1L 2T9 CANADA
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INTERNATIONAL SPECIALTY PRODUCTS, INC. Wayne, NJ ISP is the sole U.S. manufacturer of carbonyl iron products, with 65 years experience in R&D, production, QA and global distribution. Distinct characteristics of the MICROPOWDER Iron products include spherical shape, fine micron size, uniform distribution and high purity. ISP markets more than 25 MICROPOWDER Iron grades for MIM, classical PM, microwave absorbers, electronics, pharmaceutical and other applications. INTERNATIONAL TITANIUM POWDER Woodridge, IL International Titanium Powder (ITP) produces high purity commercially pure (CP) titanium and titanium alloy powders using proven proprietary Armstrong Process technology. The powders can be used in direct non-melt consolidation to end product. The Armstrong Process eliminates the need to process sponge reducing supply chain cycle time, energy consumption, manufacturing costs and environmental impact.
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KITTYHAWK PRODUCTS Garden Grove, CA Kittyhawk Products—qualified experts in the field of Hot Isostatic Processing—HIP is a process of unique benefit in solving complex design problems while increasing the strength of properties. Through our sister company, Synertech P/M, Inc., we offer unmatched net-shape capabilities with powder metal parts design and manufacture. Kittyhawk Products holds ISO9001 and AS9100 certification. MAGNESIUM ELEKTRON POWDERS Manchester, NJ Magnesium Elektron Powders is a producer of magnesium powders and specialty niche alloy powders. It has three facilities in North America, producing various types of powders. The company Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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manufactures a wide range of atomized and ground powders to military specification. The company also manufactures powders for steel desulphurization, chemical synthesis, welding applications, powder metallurgy, specialty pyrotechnics, and flameless ration-heater pads. MAKIN METAL POWDERS LTD. Rochdale, United Kingdom Makin Metal Powders (UK) Ltd are a major manufacturer of copper and copper alloy powders. The product range includes Electrolytic copper powder, Atomised copper powder both irregular and spherical, Atomised bronze powder of varying compositions in both irregular and spherical shape, Brass powders and tin powder. These powders and other specialty grades are supplied world-wide through a network of experienced agents. Contact us for further information at: www.makinmetals.com or 44-1706-717333 METAL POWDER INDUSTRIES FEDERATION Princeton, NJ Stop by to learn about membership benefits, programs, association committee activities, and any other topic of interest to you. If you have comments or ideas regarding the Federation and its services, let us know when visiting us at our booth. If your company is not a member of MPIF, you can discuss membership opportunities and benefits with someone from headquarters staff. MICROTRAC INC. Largo, FL Complete line of particle size instrumentation. Highlighting our Nanotrac 150 & 250 analyzer using dynamic light scatter for high concentration nanometer sizing from .0008-6.5 microns also our S3500 laser diffraction based analyzers. Utilizing 3 solid state lasers for easy, accurate particle analysis from .02-3000 microns. Quick wet to dry conversions, Advanced software extremely user friendly.
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NORTH AMERICAN HÖGANÄS, INC. Hollsopple, PA North American Höganäs, Inc., offers metal powder solutions that create new business and profitable growth for partners and customers. Metal powder range includes: Plain Atomized and Sponge Iron, Prealloyed Steel, Diffusion Alloyed, Stainless Steel, Tool Steel, Gas Atomized and Electrolytic Iron. Premixed and bonded Starmix materials. ORTON CERAMIC FOUNDATION Westerville, Ohio Applying more than 100 years of experience developing and producing thermal recording devices the Orton Ceramic Foundation recently introduced a new product for the powder metal industry. TempTABs provide verification of sintering consistency and reproducibility without interrupting production. TempTABs are simple to use and incorporate into SPC/ continuous improvement programs. OSTERWALDER AG Lyss, Switzerland Switzerland OSTERWALDER AG, the leading Swiss manufacturer of high performance powder compacting technology, will present the following highlights: - Servo-electrically driven CA-SP 160 Electric Powder Presses - Cross pressing / split-die technology based on CA-NC II platform - Advanced flexibility, CA-NC II line: custom configurations, multicompacting technology etc. - CA-MP, KPP and UPP: technology for cost-efficient manufacturing of multi-level compacts - Technology & Service products for increased overall equipment effectiveness Visit us at booth #504 to discuss how we can provide production solutions. PLANSEE High Performance Materials Reutte, Austria PLANSEE is the market leader in high performance materials produced by powder metallurgy. The organization
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Exhibitors has established facilities in 16 countries / 34 locations and is a trusted partner in developing material and product solutions for future technologies such as clean energy, medical technology, lighting and electronics. POMETON POWDER Venice, Italy Founded in 1940 and based in Venice, Italy, Pometon supplies its range of ferrous and non-ferrous powders to PM and other industrial clients in over 40 countries worldwide. We produce pure powders such as iron, copper (both electrolytic and atomised), bronze, brass, tin and zinc, and press-ready iron and bronze premixes. POWDER INJECTION MOULDING INTERNATIONAL Shrewsbury, England PIM International is a quarterly publication that provides in-depth industry coverage of the MIM, CIM and carbide injection moulding industries. Each issue features industry news, company reports, exclusive commissioned features and technical papers. The publisher, Inovar Communications, will also be presenting the latest “International Powder Metallurgy Directory 14th Edition 2010-2011”. www.pim-international.com/ www.ipmd.net PROMENT-PROJECT MANAGEMENT INC. Toronto, Canada Proment specializes in the manufacturing of tooling and equipment for automated manufacturing facilities. With over 40 years of experience, with emphasis on the Powder Metallurgy (PM) Industry, we develop and manufacture: CNC Hydraulic Powder Presses, Adaptors/Rigs, Tooling, Robotic Integration, Palletizing, Quality and Packaging station PTX-PENTRONIX, INC. A SUBSIDIARY OF GASBARRE PRODUCTS, INC. Lincoln Park, MI Designers and manufacturers of high-
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speed, mechanical compacting presses, 2 tons to 35 tons. Anvil and opposedram designs available. With speeds up to 300 pcs/min, and multiple cavity capabilities, extremely high production and high precision are achieved on PTX presses. PTX-Pentronix also manufactures automatic, high-speed parts-handling and robotic partspalletizing systems. Distributors for Simac Isostatic Dry Bag Presses. RIO TINTO, METAL POWDERS (QMP) Sorel-Tracy, Canada Rio Tinto, Metal Powders (QMP): registered ISO 9001, ISO 14001, ISO/TS 16949; manufactures a full product line of iron and steel powders including ATOMET standard grades, prealloys, binder treated FLOMET mixes, diffusion bonded ATOMET DB, machinable (sulphur-free) grades, sinter-hardening grades, and soft magnetic composite materials for customers worldwide.
™
RUSSELL FINEX, INC. Pineville, NC Russell vibratory screeners and separators improve particle size control and ensure that your products meet precise specification. The Compact screener is suitable for high-capacity check-screening and grading metal powders. The Vibrasonic deblinding system eliminates mesh blinding and increases screening efficiency, allowing metal powders to be accurately screened down to 20 microns. RYER, INC. Temecula, CA Ryer, Inc., is a Manufacturer, Developer and Supplier of Custom and Standard Feedstocks for the Metal Injection Molding Industry. Ryer manufactures a variety of Standard Feedstocks in addition to our Custom-Formulated Feedstocks to match your current material shrink specifications. For more information visit us on the Web at www.ryerinc.com.
SANDVIK OSPREY LTD. (Powder Group) Neath, United Kingdom United Kingdom Specialist manufacturers of high quality gas atomised powders. The MICROFINE range of pre-alloyed and master alloy powders, specifically designed for Metal Injection Moulding, covers in excess of 500 different alloys. Extensive ranges of powders for Coatings (Thermal and Cold Spray), Rapid Manufacturing, Brazing and HIPping are also offered. SCM METAL PRODUCTS, INC. Research Triangle Park, NC USA Suzhou, China A leading manufacturer of metal powders, pastes, flakes and infiltrating and brazing preforms with manufacturing facilities in the U.S. and China. Our metal powders include copper, bronze, brass, infiltration, friction copper, copper oxide, electrolytic copper, tin and lead. SCM also produces a line of specialty paste products for infiltrating and sinterbrazing PM parts as well as for furnace brazing of steel components. SINTERITE FURNACE DIVISION GASBARRE PRODUCTS, INC. St. Marys, PA Sinterite designs and manufactures continuous-belt and batch furnaces for sintering, steam-treating, annealing, brazing, and heat-treating applications. High-Temperature Pusher Furnaces (over 350 manufactured) in several designs for iron and stainless steel parts (to 3,000°F). VersaCool in-line cooling systems for sinter-hardening; Accelerated De-lubrication Systems (ADS). Alloy or Ceramic muffles available. Replacement muffles, powderhandling equipment, and fabrication products. SINTEZ-CIP, LTD. Nizhny Novgorod, Russia A proven world leader in carbonyl iron powder since 1952, SINTEZ-CIP, Russia offers you its high-quality material for a variety of applications including metal injection molding, Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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diamond tools, inductor cores, magnetorheological fluid, and more. SINTEZ-CIP IS YOUR RELIABLE SUPPLIER! Phone: +7 8313 272364, Fax: +7 8313 266210 www.sintez-cip.ru SMS MEER– A COMPANY OF THE SMS GROUP Moenchengladbach, Germany & Pittsburgh, PA In addition to equipment for pipe and long product rolling mills, forging presses and the NF metal industries, we design and build hydraulic and mechanical powder presses of which we have already sold more than 1,800. For over 50 years, we have been the competent partner for the metal powder, ceramics and tungsten carbide industry. SURFACE COMBUSTION, INC. Maumee, OH Surface Combustion offers a wide array
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of thermal processing equipment for the powder metal industry, including batch and continuous furnace systems for ferrous, non-ferrous, and stainless steel materials. Vacuum carburizing equipment and unique styles of vacuum, atmosphere or direct fired tempering equipment specifically designed for the PM markets along with Surface's wide range of endothermic and exothermic generator products will be featured. THE MODAL SHOP, INC. Cincinnati, OH Ship zero defects. The Modal Shop’s NDT-RAM systems help you deliver fully inspected PM and MIM parts, giving you and your customer confidence in the quality of your parts. NDT-RAM systems detect cracks, voids, variances in dimension, geometry, weight, density, bonding, brazing, and machine
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Exhibitors with interchangeable components to meet a variety of processing requirements, wet or dry. Sizes range from research to production-sized mills. Systems for grinding under inert gases or cryogenic grinding and metal-free grinding are offered. UNITED STATES METAL POWDERS INCORPORATED Flemington, NJ Major global producer of atomized aluminum powders, aluminum alloy premixed powders, pre-alloyed powders in addition to aluminum shot, aluminum flakes and pastes. Manufacturing facilities are operated by wholly owned subsidiaries AMPAL, Inc., located in Palmerton, PA and Poudres Hermillon SARL located in Hermillon, France.
UTRON KINETICS, LLC. Manassas, VA UTRON Kinetics, LLC., is an award winning R&D company with an exemplary history of providing advanced technological innovations to NASA, DOE, NSF, the Army, the Navy, and other organizations. We have pioneered the development and application of Combustion Driven Compaction and developed a set of globally unique technologies that are providing revolutionary improvements in materials and materials processing. VIRTO/ELCAN Mamaroneck, NY Virto/Elcan specializes in advanced screening systems used in the powdered metals industry. Kroosh technol-
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MICROMINIATURE POWDER INJECTION MOLDING—PART II
FULL-DENSITY NANOPOWDER AGGLOMERATE SINTERING OF INJECTION MOLDED IRON–NICKEL Jai-Sung Lee*, Berm-Ha Cha** and Woo-Kyung You***
INTRODUCTION AND MOTIVATION In recent years, microminiature powder injection molding has been evaluated as a shaping technology for the fabrication of microcomponents in applications such as microsystems technology.1–4 Of the several material design requirements, critical surface roughness in the submicron size range and full density are of primary importance in μPIM. These limitations are generally mitigated by using nanopowder feedstock. There are, however, problems associated with the processing of nanopowder PIM products. The most significant issue is the high cost of metal nanopowders and their explosive oxidation under atmospheric conditions. Recently, Lee et al.5,6 have suggested a new technology for fabricating μPIM parts that utilizes cost-effective metal nanopowders. They found that alloy or composite metal nanopowders in agglomerate form, produced by the hydrogen reduction of ball-milled metal oxides,7–10 can be used. By controlling the agglomerate size, it was possible to consolidate the nano-agglomerate powders by means of low-temperature pressureless sintering. The key to full-density nanopowder sintering results from the so-called NAS process in which the kinetics are governed by material transport through the hierarchical interface structures of the nanopowder agglomerates.11–14 From studies of the densification process11–14 and the diffusion process15–17 in iron–nickel nanomaterials, it was concluded that the hierarchical grain boundaries (consisting of nano-grain boundaries and agglomerate boundaries) act as preferred diffusion paths for densification, as illustrated in Figure 1. This experimental finding provides a breakthrough in processing full-density nanopowders by optimal design of the agglomerate microstructure. In this context, a modification of the agglomerated nanopowder resulting from control of the agglomerate size might be a key technology
Understanding the nanopowder agglomerate sintering (NAS) process is essential in the fabrication of small net-shape nanopowder materials and components with complex shapes. The key concept of NAS is to enhance material transport by controlling the powder-interface volume of nanopowder agglomerates. Based upon this concept, we have developed a new approach to full-density processing for the fabrication of microminiature powder injection molded (μPIM) parts using metal nanopowder agglomerates produced by the hydrogen reduction of metal oxide powders. An overview of our investigation on iron–nickel nano-agglomerate powder is presented in which the powder-interface volume is manipulated in order to control the densification process and attendant microstructures.
*Professor, **Postdoctoral Researcher, ***PhD candidate, Department of Metallurgy and Materials Science, Hanyang University, 1271 Sa 3-dong, Sangnok-gu, Kyeonggi-do, Ansan, 426-791, Korea; E-mail:
[email protected]
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FULL-DENSITY NANOPOWDER AGGLOMERATE SINTERING OF INJECTION MOLDED IRON–NICKEL
Figure 1. (a) microstructure of nanocrystalline iron–nickel alloy determined by optical and transmission electron microscopy, (b) model of hierarchical microstructure consisting of nano-grain and agglomerate boundaries16
in achieving smaller and narrower pore size distributions. In this contribution, an overview is given of our recent investigations on the full-density processing of PIM iron–nickel nano-agglomerate powders by controlling the powder-interface volume in relation to the densification process and microstructures. OPTIMAL PROCESSING OF FE-8 w/o Ni NANOPOWDER AGGLOMERATES Figure 2 is a schematic of the experimental procedure utilized for the net-shaping process of the iron–nickel nanoalloy powder.5 The process
involves a two-step procedure consisting of nanoalloy-powder synthesis by the hydrogen reduction of oxide precursors, followed by full-densification processing of the PIM nanopowder by pressureless sintering. To control the agglomerate size and size distribution, two methods were evaluated: the wet-milling of as-reduced Fe-8 w/o Ni nanopowder in a dispersant solution (stearic acid) and the crushing of agglomerates during mixing of the nanopowder with the binder material in the PIM feedstock. From our preliminary study, wetmilling proved to be more efficient than the mixing process in controlling the agglomerate structure.
Figure 2. Experimental procedure for synthesis and net-shape fabrication of metal nanopowders produced by hydrogen reduction of ball-milled oxide powder5
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Figure 3. Representative SEM micrographs of (a) as-reduced and (b) wet-milled Fe-8 w/o Ni nanopowder. Inset image in (b) is a TEM
First, Fe-8 w/o Ni nanopowder in the form of 20~30 μm size agglomerates consisting of ~100 nm particles was fabricated by the hydrogen reduction of ball-milled Fe2O3-NiO powder at 450°C for 1 h. Wet-milling to reduce agglomeration of the nanopowder by ball-milling the as-reduced nanopowder was performed in a solution of stearic acid dissolved in ethanol for 9 h. Figure 3 compares the powder morphologies of the wet-milled nanopowder with those of the asreduced powder. It can be seen that after wetmilling, the Fe-8 w/o Ni nano-agglomerate powder had a size distribution of 0.5~5 μm, reflecting a more homogeneous condition than the as-reduced powder. Basically, wet-milling of the nano-agglomerate powder resulted in an increase in the packing density of the agglomerate powder due to an improvement in the uniformity of the particle size. CONSOLIDATION OF PIM FE-8 w/o Ni NANOPOWDER BY NAS PIM of Nano-Agglomerate Powder Fe-8 w/o Ni feedstock was prepared by mixing 50 v/o wet-milled powder and 50 v/o binder Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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Figure 4. Stereo-zoom optical macrographs of PIM Fe-8 w/o Ni double-gear parts5 and three-dimensional AFM18 images of surface roughness of (a) brown part and (b) sintered part (1,000°C/1 h)
Figure 5. Fracture morphologies of (a) and (c) brown, and (b) and (d) sintered nanopowder PIM Fe-8 w/o Ni part. Inset image in (b) shows microstructure after polishing and etching. Black dotted line in (d) denotes agglomerate boundaries. SEM
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(75 v/o paraffin wax and 25 v/o stearic acid). The mixture was injection molded into a small doublegear part at 150°C. The debinding process involved melt wicking and thermal decomposition in a hydrogen atmosphere at a heating rate of 5°C/min up to 500°C and subsequently sintering with a heating rate of 10°C/min in the range 700°C– 1,000°C for various times. Figure 4 shows the shape and surface roughness of the PIM gear after debinding and sintering at 1,000°C for 1 h.18 Clearly, the PIM part keeps its fine-gear shape with a uniform full density and no distortion. This means that isotropic shrinkage occurred during the sintering process. Atomic force microscopy (AFM) confirmed that the sintered part exhibits a surface roughness of 160 nm, which is much finer than that in the brown part (0.8 μm), thereby satisfying the requirement for surface roughness in a μPIM part.
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Densification and Microstructure Figure 5 shows that the wet-milled nanopowder results in a homogeneous part after debinding and sintering. Following debinding, the brown part exhibits a homogeneous and uniform microstructure even though it has a high level of porosity (corresponding to 52% of the pore-free density), as seen in Figure 5(a). Figure 5(c) confirms that the brown part consists of uniform and homogeneous iron–nickel nanoalloy powder particles ~150 nm in size and nano pores. This uniform and homogeneous microstructure in the brown part is attributed primarily to agglomerate-size control in the wet-milling process. After sintering, the part exhibits a fully densified and nano-grain– coarsened microstructure (~1 μm grain size) with no apparent porosity (Figure 5(b)). In terms of the microstructure, full-density sintering is attributed to the uniformity and homogeneity of the brown part, which is characterized by nano-sized powder and intra-agglomerate pores. Conclusively, it should be noted that the full-density processing of nanopowder by pressureless sintering can be achieved by controlling the agglomerate-size distribution in the nanopowder. It is interesting to note that traces of interagglomerate boundaries are observed on the fracture surface of the sintered part, denoted by black dotted lines (Figure 5(d)). The sintered part of the agglomerated nanopowder consists of micron-sized agglomerate boundaries and nano-sized grain boundaries. This is important evidence of the hier-
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It is also seen that the hierarchical structure of the NAS-processed material results in a phase transformation, namely, the precipitation of γ phase in the α-matrix during sintering and s ubsequent cooling. It is clear that a large number of γ phase precipitates are located on agglomerate boundaries. This phenomenon is evidence that agglomerate boundaries are thermodynamically less stable and structurally unrelaxed than the nano-grain boundaries.5,12–17
Figure 6. Representative micrographs of hierarchical structure in PIM Fe-8 w/o Ni. (a) SEM showing agglomerate boundaries. EBSD images of the square: (b) nano-grains in agglomerate and (c) γ-precipitation primarily at agglomerate boundaries18 (sintered at 800°C for 2 h). Dotted lines in (b) and (c) denote agglomerate boundary in the square of micrograph (a)
archical structure of the PIM Fe-8 w/o Ni nanopowder. Densification in iron–nickel nanopowder proceeds by a diffusion process, preferentially along the two high-diffusivity paths, namely, agglomerate boundaries and nano-grain boundaries.12,13,16 Such hierarchical microstructures can be illustrated more clearly by electron backscattered diffraction (EBSD) images.18 Figure 6 confirms a hierarchical structure consisting of large agglomerate boundaries and nano-grain boundaries in the same PIM specimen sintered at 800°C for 2 h.
Low-Temperature-Sintered Properties Significant strengthening by grain-boundary refinement was observed in hot isostatically pressed (HIPed) Ni-20 w/o Fe nanoalloy powder with a grain size of 33 nm and a density 98% of the pore-free value.19–21 Mechanical testing revealed that over the grain-size range examined (33 to 100 nm), the yield stress increased with decreasing grain size, in agreement with the Hall-Petch relation. Can this enhanced strengthening be reproduced in the PIM iron–nickel nanoalloy part? To examine this possibility, the PIM Fe-8 w/o Ni nanopowder was sintered at 700°C for various times.18 As seen in Figure 7, the sintered part retains a fine-scale microstructure with a grain size <500 nm at a density >95% of the pore-free level after sintering for 4 h. The Vickers hardness, measured after various sintering times, is compared with that of conventional PIM Fe-8 w/o Ni with a grain size >30 μm in Table I.22,23 It is seen that the hardness achieved in the present study is significantly higher than the level for conventional PIM Fe-8 w/o Ni. Due to the grain-refinement effect, the PIM nanopowder exhibited strengthening, notwithstanding the absence of carbon. These results are indicative of promising applications for highstrength PIM iron–nickel powder materials.
Figure 7. Representative micrographs of the PIM Fe-8 w/o Ni nanopowders sintered at 700°C for (a) 1 h, (b) 2 h, (c) 4 h. TEM
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FULL-DENSITY NANOPOWDER AGGLOMERATE SINTERING OF INJECTION MOLDED IRON–NICKEL
TABLE I. GRAIN-SIZE DEPENDENCE OF HARDNESS OF PIM Fe-8 w/o Ni Grain Size
Density (% Pore-Free Density)
Hardness (Hv)
300 nm
88
300
350 nm
92
300
500 nm
95
240
1,000°C (1 h)
~1 μm
98
170
Fe-8 w/o Ni-0.9 w/o C
1,200°C (1 h)
>30 μm
98
130
[22]
MPIF Standard 35 Fe-8 w/o Ni-0.1 w/o C
1,200~1,350°C
~50 μm
98
85~130
[23]
Alloy
PIM Nanopowder
Conventional PIM Part
Composition
Fe-8 w/o Ni
Sintering Conditions
700°C (1~4 h)
SUMMARY Optimization of agglomerate-size control by wetmilling of as-reduced agglomerate nanopowders is proposed as a key technology for net-shaping nanopowder materials by PIM. PIM Fe-8 w/o Ni nanopowder exhibits a sound surface structure which satisfies the requirement for surface roughness in μPIM parts. The wet-milled nano-
Reference
This Study
powders result in homogeneous and uniform microstructures during debinding and subsequent sintering. Enhanced sintering to near-full density was achieved in the PIM Fe-8 w/o Ni nanopowder, even at a low temperature of 700°C. This resulted in a retardation of grain growth (<500 nm), leading to significant strengthening, even in the absence of carbon. This enhanced sintering effect at a low
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temperature is evidence of the NAS process which is driven by densification along hierarchical boundaries consisting of high-diffusivity paths in agglomerate and nano-grain boundaries. Such hierarchical microstructures were also found to favor γ-precipitation along agglomerate boundaries in an α-matrix. It is concluded that optimization of agglomerate-size control in nanopowders constitutes a breakthrough in the processing of netshape iron–nickel nanopowder alloys.
10.
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ACKNOWLEDGEMENTS This work has been supported financially by Ministry of Knowledge Economy in Korea through Strategic Technology Development Project (Development of Micro Functional Precision Components Manufacturing Technology— Manufacturing Technology of Micro Moving Control Parts by Powder Injection Molding). The authors are also grateful to the Ministry of Education and Science and Technology for supporting this work through the Brain Korea 21 program. REFERENCES 1. R.M. German and A. Bose, Injection Molding of Metals and Ceramics, 1997, Metal Powder Industries Federation, Princeton, NJ. 2. V. Poitter, T, Benzler, T. Gietzelt, R. Ruprecht and J. Hausselt, “Micro Powder Injection Molding”, Adv. Eng. Mater., 2000, vol. 2, no. 10, pp. 639–642. 3. Z.Y. Liu, N.H. Loh, S.B. Tor, K.A. Khor, Y. Murakoshi and R. Maeda, “Binder System for Micropowder Injection Molding”, Mater. Lett., 2001, vol. 48, pp. 31–38. 4. A. Rota, T.V. Duong and T. Hartwig, “Micro Powder Metallurgy or The Replicative Production of Metallic Microstructures”, Microsyst. Technol., 2002, vol. 8, pp. 323–325. 5. J.S. Lee, B.H. Cha and Y.S. Kang, “Processing of Netshaped Nanocrystalline Fe-Ni Material”, Adv. Eng. Mater., 2005, vol. 7, no. 6, pp. 467–473. 6. E.S. Yoon and J.S. Lee, “Densification and Microstructure of the PIMed W-15wt%Cu Nanocomposite Powder”, Journal Japan Society of Powder and Powder Metallurgy, 1999, vol. 46, no. 8, pp. 898–903. 7. J.S. Lee and T.H. Kim, “Densification and Microstructure of the Nanocomposite W-Cu Powders”, Nanostr. Mater., 1995, vol. 6, pp. 691–694. 8. X.Y. Qin, J.S. Lee, J.G. Nam and B.S. Kim, “Synthesis and Microstructural Characterization of Nanostructured γ-Ni-Fe Powder”, Nanostr. Mater., 1995, vol. 11, no. 3, pp. 383–397. 9. B.S. Kim, J.S. Lee, T. Sekino, Y.H. Choa and K. Niihara, “Hydrogen Reduction Behavior of NiO Dispersoid During
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Acrawax™ C Powder Metal Lubricants – High Performance – Clean Burning ".(110 0 %'%3%0 & %1(1&#%0 1 0 %%30 %0 %3.1( 0 4(0 %.%''%3.%0&30%04#%(0%1'0&3# (0 4(01'4 0 0%1( -0".(110 0(4&#% 0%.%''%30 (%%04&304#%(0&% ,0%1 01(0(%41'0 (40 %0#&%,0'40#&%0%1(,013#0(%#.%#01(0#& 4(&43-0".(1100& 011&'1 '%0 &30101(&%04 0. 401(&.'%0 &2% 0 4(0%04#%(0%1'0&3# (-0/0 1' 40(4&#% 0%.%''%30(%%3013#0 &3%(%#0(4%(&% -0&3.%0".(1100 & 0 **0%1' (%%,0&0& 0.4'%%'0.4 & '%013#0'%1% 0340(% &#%0 430 &3%(%#01( -0 & 0.'%130 (3&30' (&.130%3%(1% 0340%1''&.04(0 .4((4 &%0 (4#. 0&.0.130.43(& %040%3&(43%31'0%& &43 0 13#0 (31.%0.4((4 &43-0 543210/3.-,0+*0)4(4'&3%0$41#,0"''%3#1'%,0! 0* * %'0**0 0 ,010* 0 0++ 0.431.-1''%3#1'%'4321-.4
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MICROMINIATURE POWDER INJECTION MOLDING—PART II
A REVIEW OF COMPUTER SIMULATIONS IN POWDER INJECTION MOLDING Seong Jin Park*, Seokyoung Ahn**, Tae Gon Kang***, Seong-Taek Chung****, Young-Sam Kwon*****, Suk Hwan Chung******, Seong-Gon Kim*******, Seongjai Kim********, Sundar V. Atre*********, Shiwoo Lee*********, and Randall M. German**********
INTRODUCTION Powder injection molding (PIM) builds on the long-recognized success of plastic injection molding by using a high-particle-content thermoplastic as a feedstock. Steps in PIM involve first mixing selected small powders (usually <20 μm) and polymer binders. This mixture is then heated in the molding machine, pressed into a cold mold, and when the binder freezes in the mold, the component is ejected. Next, the binder is removed either thermally or by solvents and the remaining powder skeleton is then sintered to near-full density. The product may be further densified, heat treated, machined, or plated. The PIM process is practiced on a wide range of materials, including most common metals, many ceramics, and cemented carbides. The largest usage is in metal powder injection molding (MIM). Other variants are ceramic injection molding (CIM) and cemented carbide injection molding (CCIM). PIM technology includes mixing, molding, debinding, and sintering. Since PIM is a multiple-step manufacturing process, it is difficult for engineers to understand and control all of the physical phenomena involved and their interactions. A successful approach to this challenge has come from research on new models leading to computer simulation tools. In this contribution, we review the computer simulation tools available for all steps of the PIM process and discuss future trends in their application. For microminiature component manufacturing by PIM (denoted μPIM), the narrow process window will require even tighter process controls. As such, the capability to predict behavior and further optimize component design, process steps, and generally opti-
The powder injection molding (PIM) process is complicated since it is a hybrid technology embracing plastic injection molding, powder metallurgy (PM), and ceramic processing. In developing this technology, engineers have relied heavily on trial-and-error experiments. As a fundamental understanding of the inherent physical phenomena emerges, process modeling has progressed by utilizing new and customized simulation tools. These computational tools allow for parallel design of the component and process via analysis, prediction, and optimization modules. This contribution reviews computer simulation efforts and the future of this methodology.
*Assistant Professor, Mechanical Engineering, POSTECH, San 31, Hyoja-Dong, Pohang, Kyongbuk, 790-784, Korea: E-mail:
[email protected], **Assistant Professor, Mechanical Engineering, The University of Texas-Pan American, 1201 W University Dr., Edinburg, Texas 78539, USA, ***Assistant Professor, School of Aerospace and Mechanical Engineering, Korea Aerospace University, 100 Hanggongdae-gil Hwajeon-dong, GoyangCity, Gyeonggi-do 412-791, South Korea, ****Director, *****President, CetaTech, Inc., TIC 296-3, Seonjin-Ri, Sacheon-Si, Kyongnam, 664-953 Korea, ******Deputy General Manager, Hyundai Steel Co., 167-32, Kodae-Ri, Songak-Myeon, Dangjin-Gun, Chungnam, 343-711 Korea, *******Associate Professor, Dept. of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, USA, ********Associate Professor, CAVS, Mississippi State University, 200 Research Blvd., Starkville, Mississippi 39759, USA, *********Associate Professor, ONAMI, 106 Covell Hall, Oregon State University, OR 97330, **********Associate Dean of Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego California 92182-1326, USA
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mize production via computer simulation tools is even more critical. STATE-OF-THE-ART SIMULATION TOOLS Mixing Mixing is the first process after material selection. The homogeneity of the feedstock is critical to ensure uniform products with the desired properties; these are determined primarily by the mixing process.1 Furthermore, with increasing interest in miniaturized devices made of ceramic and metallic materials, μPIM is an important means for the mass production of complex micro-devices.2,3 To successfully achieve the final goal of the mass production of ceramic or metallic microdevices, it is necessary to overcome several technical barriers. Kang et al.4 developed a computer simulation tool for the Kenics mixer using the concept of chaotic mixing of viscous liquids in laminar flow based on the baker’s transformation.5 The baker’s transformation, so named by analogy with making dough, consists of repeated stretching and cutting or folding as primary mixing mechanisms. Depicted in Figure 1 are a typical geometry of the mixer, composed of a circular pipe and helically twisted rigid plates, and the progress of mixing visualized by particle distributions during the first period. The flow problem in this mixer has been solved using the finite element method (FEM) with the Cross-WLF (Williams-Landel-Ferry) model for the viscosity of the feedstock. The flow in the mixer was assumed to be isothermal Newtonian and governed by viscous force only. For the mixing analy-
sis, a particle-tracking method6 was employed where the kinematics of fluid–particle interactions were taken into account while neglecting the effect of molecular diffusion. A parallel direct solver, PARDISO7 was employed to solve the resulting sparse matrix on a parallel computer with four quad-core Opteron™ processors. A measure of mixing, the information entropy,8 based on the particle distribution was introduced to quantify mixing. The results of mixing in a continuous mixer were examined as an application of the numerical scheme, focusing on the effect of the feedstock viscosity on mixing performance. INJECTION MOLDING Flow Simulation for Filling and Packing Stages In PIM applications, the molten powder–binder feedstock mixture is highly viscous. As a result, the Reynolds number is low and the flow is modeled as a material in creep with lubrication, as treated with the Hele-Shaw formulation. With the Hele-Shaw model, the continuity and momentum equations for the melt flow in the injection molding cavity are merged into a single Poisson equation in terms of pressure and fluidity. Computer simulation is usually based on a 2.5-dimensional (2.5D) approach because of the thin wall and axial symmetry. The Hele-Shaw model has its limitations and cannot accurately describe three-dimensional (3D) flow behavior in the melt front, which is called fountain flow, and special problems arise with thick parts that exhibit sudden thickness changes,
Figure 1. Mixing simulation: (a) shaded image of mixer with 6 helical elements of Kenics static mixer, (b) progress of mixing illustrated by two colors representing fluid–particle mixtures4
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which cause race-track flow. Currently, several 3D computer-aided engineering (CAE) simulations exist that successfully predict conventional plastic advancement and pressure variation with changes in component design and forming parameters.9 For PIM 3D simulation, Hwang and Kwon10 developed a filling simulation with slip using an adaptive mesh refinement technique to capture the large deformation of the free surfaces. However, this is computationally intensive,10–13 so further research is moving toward simplified solution routes.9 For a more rigorous approach during the filling process, a limited number of studies have invoked a full 3D model, and have included fountain flow, viscoelastic constitutive models, slip phenomena, yield phenomena, and inertial effects in governing equations and the interface.9,11–12,14 For 2.5D numerical analysis of filling and packing in PIM, both the pressure and energy equations must be solved during the entire filling and packing cycle. This is achieved using FEM for the Poisson equa-
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
tion and energy equation while a finite difference method (FDM) is used in the thickness direction, called one FDM-FEM hybrid scheme.9 The FEM has excellent flexibility in treating complex geometries and irregular boundaries, which is a key advantage of this method. In μPIM, the powder–binder separation is critical. Basically, the injection molding step in PIM involves the flow of a concentrated suspension (powder/binder mixture) in a closed die. At high shear rates, the powders tend to separate from low-density binders, resulting in a nonuniform powder distribution, accompanied by significant changes in viscosity. Since the filling of a mold cavity depends on the viscosity of the mixture, separation of the powder from the binder is detrimental to uniform component fabrication.15–16 Phillips et al.17 have proposed a particle diffusive model combined with flow equations, which can be applied to solve the flow patterns in PIM, taking into consideration the local deformation rate.
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Heat-Transfer Simulation for Cooling Stage In the PIM mold-cooling process, the convection and dissipation terms in the energy equation are neglected since the velocity of a feedstock melt in the cooling process is almost zero.18–20 Therefore, the objective of the mold-cooling analysis is to solve the temperature profile at the cavity surface to be used as the boundary condition of the feedstock melt during the filling and packing analysis. When the injection molding process is in steady-state, the mold temperature will fluctuate periodically over time due to the interaction between the hot melt and the cold mold and circulating coolant. To reduce the computational time for this transient process, a 3D cycle-average approach is adopted for the thermal analysis to determine the cycleaveraged temperature field and its effects on the PIM component. Although the mold temperature is assumed invariant over time there is still a transient for the PIM feedstock.21 Note that the boundary conditions for the mold and PIM feedstock cooling are coupled. For a more rigorous approach during the cooling process, some researchers have included more than two different mold materials with a flow analysis that includes the cooling channel details. This enables a corresponding heattransfer analysis with any special cooling elements, such as baffles, fountains, thermal pin, or heat pipes.19 For the numerical analysis of the cooling process in PIM, the boundary element method (BEM) is widely used due to its advantage in a reduction of the dimensionality of the solution. The BEM discretizes the domain boundary rather than the interior of the physical domain. As a result, the volume integrals become surface integrals, and the
number of unknowns, computation effort, and mesh generation are significantly reduced.9 Commercial Simulation Tools In the numerical analysis of injection molding, several numerical packages are available for conventional thermoplastics and one may try to apply the same numerical-analysis techniques to PIM. However, the rheological behavior of a powder– binder feedstock mixture is significantly different from that of a thermoplastic. Hence, the direct application of methods developed for thermoplastics to PIM requires caution.10,14 Commercial software packages, including Moldflow (Moldflow Corp., Framingham, Massachusetts), Moldex3D (CoreTech System Co., Ltd., Chupei City, Taiwan), PIMsolver (CetaTech, Sacheon, Korea), and SIMUFLOW (C-Solutions, Inc., Boulder, Colorado) are available for PIM simulation. In addition, several research groups have written customized codes, but generally these are not released for public use. It is well known that powder–binder feedstock mixtures used in PIM exhibit a peculiar rheological feature known as wall slip.14,22 Therefore, a numerical simulation of the PIM process requires a constitutive equation representing the slip phenomena of powder–binder feedstock mixtures.14,21 Figure 2 shows a filling-cooling coupled analysis during PIM, reported with verification and its accuracy.21 DEBINDING The debinding process removes the polymeric binder system from the injection molded compact. There are several different methods for debinding, including solvent debinding, thermal debinding,
Figure 2. Injection molding simulation: (a) cooling channel layout and part geometry for U-shaped specimen, (b) filling pattern21
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catalytic debinding, and wicking. Of these, the most computer simulations have been developed for thermal debinding. The thermal-debinding process is the most time consuming and results in the formation of some defects. The overall removal of the residual polymer involves a complex combination of heat transfer in a porous polymer, pyrolysis, and liquid and gas migration. Several publications describe models for these phenomena with numerical simulations mostly based on FDM.23–33 Computer simulation can help reduce the debinding process time and increase productivity, as well as helping avoid defect formation by calculating the critical gas pressure to initiate cracks. SINTERING Constitutive Relations Continuum modeling of the sintering process is the most relevant approach to modeling grain growth, densification, and deformation. Key contributions have been made by Ashby,34–36 McMeeking and Kuhn,37 Olevsky et al.,38–41 Riedel
et al.,42–43 McHugh and Riedel,44 Bouvard and Meister,45 Cocks,46 Kwon et al.,47–48 and Bordia and Scherer49–51 based on sintering mechanisms such as surface diffusion, grain-boundary diffusion, volume diffusion, viscous flow (amorphous materials), plastic flow (crystalline materials), evaporation–condensation, and rearrangement. For industrial applications, the phenomenological models are used for sintering simulations with the following key physical parameters: • Sintering stress52 is the driving force for sintering due to the interfacial energy of pores and grain boundaries. The sintering stress depends on surface energy, density, and geometric parameters such as grain size when all the pores are closed in the final process. • Effective bulk viscosity is the resistance to densification during sintering and is a function of the material, porosity, grain size, and temperature. Models for the effective bulk viscosity display various forms, depending on the assumed dominant sintering mechanism. • Effective shear viscosity is the resistance to
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deformation during sintering and is also a function of the material, porosity, grain size, and temperature. Several rheological models for the effective bulk viscosity are available. The cited parameters are functions of grain size. Therefore, a grain-growth model is needed for the accurate prediction of densification and deformation during sintering. Typical initial and boundary conditions for the sintering simulations include the following: • Initial condition: mean particle size and grain size of the green compact for grain growth and initial green-density distribution for densification obtained from compaction simulations. • Boundary conditions: surface energy condition imposed on the free surface and friction condition of the component depending on its size, shape, and contact with the substrate support. The initial green-density distribution within the shaped body imposes the necessity to start the sintering simulation with the output from an accurate compaction simulation, since die compaction induces green-density gradients that depend on the material, pressure, rate of pressurization, tool motions, and lubrication. The initial and boundary conditions help to determine the shape distortion during sintering from gravity, nonuniform heating, and from density gradients in the green body.
of simulation tools have selected explicit and implicit algorithms for time advancement, as well as numerical contact algorithms for problems such as surface separation, and remeshing algorithms that are required for large deformations such as those seen in some sintered materials in which up to 25% dimensional contraction is possible. Figure 3 shows a sintering simulation for a tungsten heavy alloy.
Numerical Method Even though many numerical methods have been developed, FEM is most popular for continuum models of the pressing and sintering processes. Many powerful commercial software packages are available for calculating two-dimensional (2D) and 3D thermo-mechanical processes operative during sintering. To increase accuracy and convergence speed for sintering simulations, developers
Multiscale Simulation Numerical methods have been developed not only on a continuum scale but also on other scales such as electronic, atomistic, and meso. In addition, as the need for miniaturization of components increases, simulations on smaller scales become more significant in light of their narrow process window, which requires an understanding of the attendant scientific fundamentals. Figure 5 shows one example of multiscale simulations in PIM including: • Atomistic simulation using the modified embedded atom method (MEAM) originally proposed by Baskes et al.53,54 and development of a two-particle model from the atomistic simulation results55 • Electronic scale quantum mechanical simulation based on density functional theory (DFT)56,57 and development of an activator/ inhibitor model from electronic simulation results58 • Mesoscale simulation using the discrete element method (DEM) by calculating the inter-
Figure 3. Sintering simulation for a tungsten heavy alloy: injection molded part and shape before and after sintering
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FUTURE TRENDS Historical Integration of PIM Simulations As a result of efforts in developing models and simulation tools, it is now possible to simulate numerically most of the individual processes in PIM, not only in academe, but also by means of commercial software. Figure 4 shows one example of how to integrate simulation tools based on continuum mechanics. One advantage of this integration is that the powder concentration prediction during injection molding can be considered as the initial condition for debinding and sintering. As a consequence of this integration, a sensitivity analysis and optimization during the entire PIM process may be possible. The measurement of material properties and their database are critical in this integration and a material informatics concept can be used, as will be discussed.
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Figure 4. Historically integrated modeling, simulation, and optimization
Figure 5. Multiscale modeling and simulation Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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Figure 6. Current research activities on material informatics in PIMMultiscale modeling and simulation
actions between contacting grains modeled by atomistic simulation and development of a continuum-based model from DEM simulation results • Continuum-based macroscale simulation The smaller-scale simulation can be considered as a virtual experiment for obtaining material parameters for higher-scale simulations. Sometimes a lower-scale experiment is impossible, but can be replaced by a lower-scale simulation. In atomistic simulations, the Monte-Carlo (MC) method is frequently used. The fluid–particle interaction can be simulated numerically by DEM. Furthermore, multiscale sensitivity analysis and optimization can be introduced. Material Informatics Informatics is a science in which a new knowledge system is developed by collecting, storing, processing, retrieving, indexing, extracting, exchanging, transmitting, analyzing, studying, and classifying data. Figure 6 shows some examples of current activities in PM material informatics, including PIM. These activities embrace: • Establishing a database of terminology, models and equations, figures, and experimental data
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• A graphic capability to make plots and curvefitting capability to obtain material parameters • A simulation capability based on a material parameter database The concept of the “computational thinking” algorithm from material informatics provides useful information such as the prediction of missing data points, a reduction in the number of experiments for material properties, validation and verification, and generation of material–process–property mapping. SUMMARY A review of state-of-the-art models and simulation tools in PIM based on continuum theory is given, including mixing, injection molding, debinding, and sintering. Due to the complexity of the PIM process and the increasing demand for miniaturization of components, computer simulation tools are becoming more useful and necessary. In the future, integration of developed simulations into multiscale simulations, and the need for organized materials information will be critical. REFERENCES
1. R.M. German, Powder Injection Molding Design & Applications: User’s Guide, Innovative Materials Solutions, State College, PA, 2003.
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2. V. Piotter, N. Holstein, K. Plewa, R. Ruprecht and J. Hausselt, “Replication of Micro Components by Different Variants of Injection Molding”, Microsystem Technologies, 2004, vol. 10, pp. 547–551. 3. Z.Y. Liu, N.H. Loh, S.B. Tor, K.A. Khor, Y. Murakoshi and R. Maeda, “Production of Micro Components by Micro Powder Injection Molding”, Journal of Materials Science Letters, 2001, vol. 20, no. 4, pp. 307–309. 4. T.G. Kang, S. Ahn, S.J. Park, S.V. Atre and R.M. German, “Mixing Simulation for Powder Injection Moulding Feedstock: Quantification and Sensitivity Analysis”, PIM International, 2009, vol. 3, no. 2, pp. 59–62. 5. J.M. Ottino, The Kinematics of Mixing: Stretching, Chaos, and Transport, 1989, Cambridge University Press, Cambridge, UK. 6. T.G. Kang and T.H. Kwon, “Colored Particle Tracking Method for Mixing Analysis of Chaotic Micromixers”, Journal of Micromechanics and Microengineering, 2004, vol. 14, pp. 891–899. 7. O. Schenk and K. Gärtner, “Solving Unsymmetric Sparse Systems of Linear Equations with PARDISO”, Future Generation Computer Systems, 2004, vol. 20, no. 3, pp. 475–487. 8. C.E. Shannon, “The Mathematical Theory of Communication,” Bell System Technical Journal, 1948, vol. 27, pp. 379–423. 9. S. Kim and L. Turng, “Developments of Three-Dimensional Computer-Aided Engineering Simulation for Injection Molding”, Modeling and Simulation in Materials Science and Engineering, 2004, vol. 12, pp. 151–173. 10. C.J. Hwang and T.H. Kwon “A Full 3D Finite Element Analysis of the Powder Injection Molding Filling Process Including Slip Phenomena”, Polymer Engineering and Science, 2002, vol. 42, no. 1, pp. 33–50. 11. K. Mori, K. Osakada and S. Takaoka, “Simplified Three-
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20. S.J. Park and T.H. Kwon, “Thermal and Design Sensitivity Analyses for Cooling System of Injection Mold, Part 1: Thermal Analysis”, ASME Journal of Manufacturing Science and Engineering, 1998, vol. 120, pp. 287–295. 21. S. Ahn, S.T. Chung, S.V. Atre, S.J. Park and R.M. German, “Integrated Filling, Packing, and Cooling CAE Analysis of Powder Injection Molding Parts”, Powder Metallurgy, 2008, vol. 51, no. 4, pp. 318–326. 22. D.M. Kalyon, “Apparent Slip and Viscoplasticity of Concentrated Suspensions”, Journal of Rheology, 2005, vol. 49, no. 3, pp. 621–640. 23. R.M. German, “Theory of Thermal Debinding”, Int. Journal of Powder Metall., 1987, vol. 23, no. 4, pp. 237–245. 24. P. Calvert and M. Cima, “Theoretical Models for Binder Burnout”, Journal of the American Ceramic Society, 1990, vol. 73, no. 3, pp. 575–579. 25. M.R. Barone and J.C. Ulicny, “Liquid-Phase Transport During Removal of Organic Binders in Injection-Molded Ceramics”, Journal of the American Ceramic Society, 1990, vol. 73, no. 11, pp. 3,323–3,333. 26. G.C. Stangle and I.A. Aksay, “Simultaneous Momentum, Heat and Mass Transfer with Chemical Reaction in a Disordered Porous Medium: Application to Binder Removal From a Ceramic Green Body”, Chemical Engineering Science, 1990, vol. 45, no. 7, pp. 1,719–1,731. 27. D.-S. Tsai, “Pressure Buildup and Internal Stresses During Binder Burnout: Numerical Analysis”, AIChE Journal, 1991, vol. 37, no. 4, pp. 547–554. 28. J.R.G. Evans, M.J. Edirisinghe, J.K. Wright and J. Crank, “On the Removal of Organic Vehicle from Molded Ceramic Bodies”, Pro. Royal Society London A, 1991, vol. 432, pp. 321–340. 29. S.A. Mater, M.J. Edirisinghe, J.R.G. Evans, E.H. Twizell and J.H. Song, “Modelling the Removal of Organic Vehicle from Ceramic or Metal Mouldings: The Effect of Gas Permeation on the Incidence of Defects”, Journal of Materials Science, 1995, vol. 30, pp. 3,805–3,810. 30. J.A. Lewis and M.A. Galler, “Computer Simulations of Binder Removal from 2-D and 3-D Model Particulate Bodies”, Journal of the American Ceramic Society, 1996, vol. 79, no. 5, pp. 1,377–1,388. 31. A. Maximenko and O. Van Der Biest, “Finite Element Modelling of Binder Removal From Ceramic Mouldings”, Journal of the European Ceramic Society, 1998, vol. 18, no, 8, pp. 1,001–1,009. 32. A.C. West and S.J. Lombardo, “The Role of Thermal and Transport Properties on the Binder Burnout of InjectionMolded Ceramic Components”, Chemical Engineering Journal, 1998, vol. 71, no. 3, pp. 243–252. 33. Y.C. Lam, S.C.M. Yu, K.C. Tam and Y. Shengjie, “Simulation of Polymer Removal from a Powder Injection Molding Compact by Thermal Debinding”, Metallurgical and Materials Transactions A, 2000, vol. 31, pp. 2,597–2,606. 34. M.F. Ashby, “A First Report on Sintering Diagrams”, Acta Metallurgica, 1974, vol. 22, pp. 275–290. 35. F.B. Swinkels and M.F. Ashby, “A Second Report on Sintering Diagrams”, Acta Metallurgica, 1981, vol. 29, pp. 259–281. 36. A.S. Helle, K.E. Easterling and M.F. Ashby, “Hot Isostatic Pressing Diagrams: New Developments”, Acta Metallurgica, 1985, vol. 33, pp. 2,163–2,174. 37. R.M. McMeeking and L. Kuhn, “A Diffusional Creep Law for Powder Compacts”, Acta Metallurgica Materialia, 1992, vol. 40, no. 5, pp. 961–969. 38. E. Olevsky, V. Skorohod, M. Bohsmann and G. Petzow, “Computer Modeling of Sintering with Phase Transformations”, Sintering and Materials, edited by L. Nan, International Academic Publishers, Wuhan, China, 1995, pp. 9–14. 39. E.A. Olevsky, “Theory of Sintering: From Discrete to Continuum”, Materials Science and Engineering, 1998, vol. R23, pp. 41–100.
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40. V. Tikare, M.V. Braginsky, E.A. Olevsky and R.T. Dehoff, “A Combined Statistical-Microstructural Model for Simulation of Sintering”, Sintering Science and Technology, edited by R.M. German, G.L. Messing and R.G. Cornwall, Pennsylvania State University, State College, PA, 2000, pp. 405–409. 41. V. Tikare, E.A. Olevsky and M.V. Braginsky, “Combined MacroMeso Scale Modeling of Sintering. Part II, Mesoscale Simulations”, Recent Developments in Computer Modeling of Powder Metallurgy Processes, edited by A. Zavaliangos and A. Laptev, ISO Press, Ohmsha, Sweden, 2001, pp. 94–104. 42. H. Riedel, D. Meyer, J. Svoboda and H. Zipse, “Numerical Simulation of Die Pressing and Sintering—Development of Constitutive Equations”, Int. J. of Refractory Metals and Hard Materials, 1994, vol. 12, no. 2, pp. 55–60. 43. T. Kraft and H. Riedel, “Numerical Simulation of Die Compaction and Sintering”, Powder Metallurgy, 2002, vol. 45, no. 3, pp. 227–231. 44. P.E. McHugh and H. Riedel, “A Liquid Phase Sintering Model: Application to Si3N4 and WC-Co”, Acta Metallurgica Materialia, 1997, vol. 45, no. 7, pp. 2,995–3,003. 45. D. Bouvard and T. Meister, “Modelling Bulk Viscosity of Powder Aggregate During Sintering”, Modeling and Simulations in Material Science and Engineering, 2000, vol. 8, no. 3, pp. 377–388. 46. A.C.F. Cocks, “The Structure of Constitutive Laws for the Sintering of Fine Grained Materials”, Acta Metallurgica Materialia, 1994, vol. 42, no. 7, pp. 2,191–2,210. 47. Y.S. Kwon and K.T. Kim, “High Temperature Densification Forming of Alumina Powder—Constitutive Model and Experiments”, Journal of Engineering Materials and Technology, 1996, vol. 118, no. 4, pp. 448–455. 48. Y.S. Kwon, Y. Wu, P. Suri and R.M. German, “Simulation of the Sintering Densification and Shrinkage Behavior of PowderInjection-Molded 17-4 PH Stainless Steel”, Metallurgical and Materials Transactions A, 2004, vol. 35, pp. 257–263. 49. R.K. Bordia and G.W. Scherer, “On Constrained Sintering—I. Constitutive Model for a Sintering Body”, Acta Metallurgica Materialia, 1988, vol. 36, no. 9, pp. 2,393–2,397. 50. R.K. Bordia and G.W. Scherer, “On Constrained Sintering—II. Comparison of Constitutive Models”, Acta Metallurgica Materialia, 1988, vol. 36, no. 9, pp. 2,399–2,409. 51. R. K. Bordia and G. W. Scherer, “On Constrained Sintering— III. Rigid Inclusions”, Acta Metallurgica Materialia, 1988, vol. 36, no. 9, pp. 2,411–2,416. 52. R.M. German, Sintering Theory Practice, John Wiley & Sons, Inc., New York, NY, 1996. 53. M.I. Baskes, J.S. Nelson and A.F. Wright, “Semiempirical Modified Embedded-Atom Potentials for Silicon and Germanium,” Physical Review B, 1989, vol. 40, no. 9, pp. 6,085–6,100. 54. M.I. Baskes, “Modified Embedded-Atom Potentials for Cubic Materials and Impurities”, Physical Review B, 1992, vol. 46, no. 2, pp. 2,727–2,742. 55. A. Moitra, S. Kim, J. Houze, B. Jelinek, S.J. Park, R.M. German and S.G. Kim, “Melting Tungsten Nanoparticles: A Molecular Dynamics Study”, Journal of Physics D: Applied Physics, 2008, vol. 41, pp. 185,406–185,412. 56. W. Kohn and L.J. Sham, “Self-Consistent Equations Including Exchange and Correlation Effects”, Physical Review, 1965, vol. 140, no. 4A, pp. A1,133–A1,138. 57. G. Kresse and J. Furthmüller, “Efficient Iterative Schemes for ab initio Total-Energy Calculations Using a Plane-Wave Basis Set”, Physical Review B, 1996, vol. 54, no. 16, pp. 11,169–11,186. 58. J. Houze, S. Kim, S.J. Park, R.M. German, M.F. Horstemeyer and S.G. Kim, “The Effect of Fe Atoms on the Adsorption of a W Atom on W(100) Surface”, Journal of Applied Physics 2008, vol. 103, no. 10, pp. 106,103–106,105. ijpm
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Serving the world of powder metallurgy MPIF is the world’s largest PM trade association, growing the powder metallurgy industry for the benefit of its member companies and the greater PM industry through: • Annual PowderMet conference & trade exhibition • Educational seminars and e-learning courses • Development and promulgation of standards • Market development and public relations • The world’s most extensive PM publications department • Dissemination of information via a family of Web sites SINCE 1944, THE VOICE OF PM Metal Powder Industries Federation 105 College Road East Princeton, New Jersey 08540-6692 U.S.A. E-mail:
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2011 International Conference on Powder Metallurgy & Particulate Materials May 18–21 • Marriott Marquis • San Francisco, California NEW DATES & LOCATION
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MICROMINIATURE POWDER INJECTION MOLDING—PART II
CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLDFILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING Sachin G. Laddha*, Carl Wu**, Seong-Jin Park*****, Shiwoo Lee***, Seokyoung Ahn****** Randall M. German*******, and Sundar V. Atre****
INTRODUCTION Microsystem technologies have influenced the development of microand multiscale manufacturing techniques during the last decade.1,2 This contribution addresses the net-shaping of miniaturized components from metals and ceramics by PIM. This technology offers advantages in shape complexity, materials utilization, energy efficiency, low-cost production, and mass manufacturing.3–5 A major area of application is in microfluidic systems.6–12 Other applications are foreseen in diverse areas such as microelectronic and MEMS packaging, optical transmission networks, telecommunication systems, minimally invasive surgical tools, circuit-board micro-drills, and automotive sensors. In some miniature devices, ceramics (carbides, nitrides, borides, oxides) are the material of choice because of density, wear-resistance, radio-opacity, arcresistance, inertia, stiffness, hardness, strength, biocompatibility, thermal expansion coefficient, or vapor-pressure considerations. An experimental platform with complimentary modeling is used in research on the PIM of ceramic microchannel arrays (MCAs). The main objective is to investigate the issue of material heterogeneity through the development of the μPIM process for MCAs such as those illustrated in Figure 1. MCAs were selected since they are widely used in microsystems applications; examples include microfluidics, microoptics, microheat exchangers, microtransducers, and medical devices. Shrinking component sizes taxes our fabrication abilities. Micromolding with polymers has met with some success,13,14 but material
While micromolding with polymers has met with success, material homogeneity remains a critical issue in powder injection molding (PIM) because separation of the powder and binder results in defects in metal or ceramic microparts. Material heterogeneity, or an inhomogeneous particle distribution, in green parts is related to inhomogeneous feedstock mixtures and to powder/binder separation occurring in melt flow. This is a major issue in microminature powder injection molding (μPIM) because of the small particle sizes and high mold-flow velocities in filling. Also, small and irregular-shaped particles tend to agglomerate in the feedstock and fast mold filling may enhance particle migration because of the increased shear-rate gradient in the cavity. These issues prompted this study on the influence of material, processing conditions, and component geometry in the evolution of problems due to homogeneity in microparts such as microchannel arrays (MCAs). The present work focuses on characterization and application of simulation techniques to understand the origin and evolution of macroscale mold filling defects during μPIM.
*Scientist, Pacific Northwest National Laboratory, Richland, Washington, USA; **R&D Engineer, Hewlett Packard, ***Assistant Professor, ****Associate Professor, Oregon Nanoscience and Microtechnologies Institute, Oregon State University, 106 Covell Hall, Corvallis, Oregon, USA; E-mail:
[email protected], *****Assistant Professor, Department of Mechanical Engineering, Pohang University of Science & Technology (POSTECH), Pohang, Republic of Korea; ******Assistant Professor, Department of Mechanical Engineering, The University of Texas-Pan American, Edinburg, Texas, USA; *******Associate Dean of Engineering, College of Engineering, San Diego State University, San Diego California, USA
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CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLD-FILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING
(a)
(b)
Figure 1. (a) PIM MCA, (b) 50 μm channel in MCA (magnified view)
homogeneity is critical in PIM because it results in various molding defects in metal or ceramic microparts.15,16 These issues have resulted in a focus on the influence of material processing conditions and component geometry on the evolution of molding defects in microparts such as microchannel arrays (MCAs), as shown in Figure 2. Computer simulations of mold-filling behavior in MCAs were analyzed using Moldflow Plastic Insight (MPI) software. This is a commercial tool used by the plastics-processing industry, particularly for plastic injection molding. By using Moldflow, the
injection molding process simulations can be carried out on a single solid model in which the bulk and microcavities are meshed with solid elements of differing resolution to achieve the required precession and simulation efficiency. The tool is able to predict melt-flow behavior and potential defects under simulated processing conditions. MCA features in the study were designed with a specific geometry and dimensions in terms of different channel wall width, thickness, channel width, and channel length. The flat circular pad at the end of the component was designed to locate
Figure 2. Mold-filling defects in MCA, (a) optical microscopy, (b) laser surface profilometry
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CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLD-FILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING
the thermal-sensor tip in the model cavity for process monitoring. The bulk size of the small parts with 50 μm ribs was ~2.5 × 8 × 1.5 mm (width × length × thickness), with a volume ~48 mm3 and weight of 0.12 g. The small part was designed with an aspect ratio of 2:1 for the microchannel walls and a large flow-path ratio of 80 (length:thickness). Figure 3 shows the progressive filling of the microchannels from Moldflow simulations using alumina feedstock (BASF Catamold AO-F) at a
melt temperature of 190°C. It can be observed that only after the bulk is filled halfway do the microchannels begin to fill. The microchannels are filled last which causes uneven filling of the part and results in uneven cooling and stress generation in the MCA, accompanied by molding defects. Based on these observations, the present study examined the primary factors that influence microchannel-cavity filling. To meet this objective, various feedstock properties were evaluated in conjunction with changes in process parameters and component geometry for MCAs. The material properties included rheological behavior, pressure–volume–temperature (PVT) behavior, and thermal properties (specific heat, thermal conductivity, coefficient of thermal expansion, transition temperature). The process parameters included melt temperature and mold temperature, injection speed, injection pressure, and packing pressure. Geometric variables included bulk thickness and gate size. RESULTS & DISCUSSION Material Properties Rheology The rheological characteristics of the feedstock were examined by means of a capillary rheometer (Gottfert Rheograph 2003) at different shear rates and temperatures in accordance with ASTM D 3835. The temperatures were between the highest melting temperature and the lowest degradation temperature of the binder system. A 1 mm dia. barrel and die length of 20 mm were used. The feedstock viscosity decreases with increasing shear rate. Normally, feedstocks that exhibit shear-thinning flow behavior during molding facilitate mold filling and minimize jetting. Figure 4
Figure 3. Progressive filling of microchannels using alumina feedstock at a melt temperature of 190°C based on Moldflow simulations Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Figure 4. Relationship between viscosity, temperature, and shear rate for alumina feedstock
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CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLD-FILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING
shows the relation between viscosity, shear rate, and temperature. The rheological data were fitted to a modified Cross-WLF equation: η0 (T,P ) η (T,γ,P ) = –––––––––––––––––– η0 (T ) × γ (1–n) 1+ –––––––––– τ*
[
{
]
–[A1 (T–T *)] T ≥ T*, η0(T,P ) = D1 x e ––––––––––––– [A2 + (T–T *)] T < T*, η0 (T,P ) = ∞ where A2 = A2 + D3 × P T = D2 + D3 × P
}
}
(1)
η0 is the zero-shear-rate viscosity, γ is the shear rate, T is the temperature, p is the pressure, and n, τ*, D1, D2, D3, A1, and A2 are model constants. Most feedstocks exhibit two regimes of flow behavior: Newtonian and shear thinning. Newtonian behavior occurs at low shear rates when the shear stress–to–shear rate relationship is linear. At highTABLE I. ALUMINA FEEDSTOCK PARAMETERS Coefficient
Definition
Value
n
Power-law index
0.48
τ* (Pa)
Constant with Weissenberg– Rabinowitsch correction at user’s specification during data fit; this value is used for material database
D1 (Pa-s)
Scale factor for viscosity
D2 (K)
Glass transition temperature at zero gage pressure
A1
WLF temperature-shift factor
30.72
A2 (K)
WLF temperature-shift factor
51.6
24820
1.27E+14 263
er shear rates, viscosity decreases as the shear rate increases; this behavior is termed shear thinning. In the Cross-WLF equation, the transition between the Newtonian and shear-thinning regimes is characterized by the parameter τ*, which represents the shear stress at which the onset of shear-thinning behavior occurs. The value of (1 – n) represents the slope of the shear-thinning curve where n is a power-law coefficient in the model. The remaining constants are used to model the zero-shear rate viscosity, η0. The parameter Tb characterizes the temperature sensitivity of η0; it depends on temperature, especially near Tg. Table I gives the values and definitions of these constants for the alumina feedstock. For simulation, the values of the rheological constants were varied in Moldflow to examine the effect of individual parameters/constants on the filling of microchannels. Figure 5 shows the change in viscosity as a function of shear rate by changing the value of n from 0.48 to 0.88. In a similar manner, other fitting parameters were varied. It was observed that increasing the values of n and τ* increases the Newtonian behavior of the feedstock. However, increasing the value of D1 decreased the Newtonian behavior of the feedstock. The other parameters showed no significant sensitivity towards mold-filling behavior. Hence, the mold filling studies were carried out on alumina feedstock to see the effect of changes in these parameters on flow in the microchannels. Figure 6 shows the effect of changes in n and τ* on filling behavior of the microchannels. Increasing the values of n and τ* increased the flow of feedstock into the microchannels. Thus, the feedstock exhibiting Newtonian behavior shows a higher flow in the microchannels
Figure 5. Influence of viscosity constant (n) and temperature on rheological behavior, (a) n = 0.48, (b) n = 0.88
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CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLD-FILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING
Figure 6. Effect of a change in viscosity constants on flow in microchannels. Mold temperature = 150°C, melt temperature = 220°C, (a) τ* = 24,820, (b) n = 0.48
than a feedstock exhibiting non-Newtonian behavior. A possible reason for this difference in response is the build-up in cavity pressure with Newtonian behavior that forces the feedstock to flow into the thin microchannels. PVT The pressure–volume–temperature relation helps in understanding compression and temperature effects during a typical injection molding cycle. The hold pressure should be selected by reference to the PVT diagram such that the residual cavity pressure is near atmospheric pressure before demolding. A PVT apparatus (Gnomix) was used to characterize the feedstock in accordance with ASTM D 792. Measurements involved isothermal heating and constant rate heating at ~3°C/min. The PVT behavior of the alumina feedstock is shown in Figure 7 for the specific volume change of the melt expected in the cavity as a function of cavity pressure and temperature. Table II gives the values of
PVT feedstock coefficients. Data analysis was performed using a modified Tait two-domain empirical model that defines two domains above and below a transition temperature Tt:
[
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
)
]
where υ is the specific volume in cm3/g, T is the temperature in °C, P is the pressure in MPa, C is a dimensionless constant, B(T) is a temperaturedependent parameter with the same dimension as pressure, υ0 and υf are the specific volumes at room temperature and at temperatures above the TABLE II. PVT FEEDSTOCK COEFFICIENTS Coefficients
Definition
b5 (K)
Crystallization temperature
4.360 E+02
b6 (K/Pa)
Pressure sensitivity of b5
6.000 E-08
b1m (m3/kg)
Tait constant for melt
3.827 E-04
b2m (m3/kg-K) Tait constant for melt
1.258 E-07
b3m (Pa)
Tait constant for melt
3.970 E+08
b4m (1/K)
Tait constant for melt
2.174 E-03
b1s (m3/kg)
Tait constant for solid
3.692 E-04
b2s (m3/kg-K) Tait constant for solid
8.316 E-08
b3s (Pa)
Tait constant for solid
7.000 E+08
b4s (1/K)
Tait constant for solid
5.947 E-03
b7 (m3/kg)
Transition of specific volume from solid to melt
1.347 E-05
Transition of specific volume from solid to melt
2.702 E-01
Transition of specific volume to melt
1.926 E-08
b8 (1/K) Figure 7. Feedstock PVT relationships
(
P ) +υ (T,P ) -1 (2) υ(T,P )= υ0(T )×(1–C×1n 1+ –––– f B(T )
b9 (1/Pa)
Value
53
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CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLD-FILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING
transition temperature, respectively. The specific volume at temperatures higher than the transition temperature is given by: T ≥ Tf, υ0(T ) = b1m + b2m × T*
function of time for different values of specific heat. A decrease in specific heat of the feedstock reduced flow in the microchannels.
(3)
where T* is any specific temperature above the transition temperature. B(T ) can be expressed as: B(T ) = b3m × e (–b4n × T*)
(4)
However, the specific volume at the transition temperature is considered to be zero while heating the feedstock. It is represented by the equation: υf (T,P ) = 0
(5)
The specific volume at temperatures lower than the transition temperature is given by: T < Tf, υ0 (T) = b1s + b2s × T*
Figure 8. Specific heat as a function of feedstock temperature
(6)
where the feedstock is in the solid and semi-solid states. B(T ) can be expressed as: B(T ) = b3s × e (–b4s × T*)
(7)
where T* is any specific temperature below the transition temperature. During cooling the specific volume is given by the relation: υf (T,P) = b7 × e(b8 x T * –b9 × P )
(8)
The subscripts m and s refer to the melt and solid, respectively. An extensive sensitivity analysis study was conducted on the parameters in Table II. No significant change in the microchannel-filling behavior was observed by changing these constants by 10% from the experimental values for both the feedstocks. Specific Heat Specific-heat measurements were made by differential scanning calorimetry (PerkinElmer DSC-7) in accordance with ASTM E 1269. The cooling rate was 20°C/min. Figure 8 shows the variation in specific heat with the temperature of the feedstock The effect of a change in specific heat on the mold-filling behavior of the feedstock was determined. Figure 9 shows the comparison of the percentage fill in microchannels vs. bulk filling as a
54
Figure 9. Comparison of fill in microchannels to bulk as a function of time for different values of specific heat for feedstock. Mold temperature 150°C
Figure 10. Thermal conductivity data for feedstock Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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Figure 11. Effect of melt temperature of feedstocks on filling of microchannels, bulk, and complete fill of the μPIM part, (a)melt temperature 190°C, (b) melt temperature 170°C
Thermal Conductivity The thermal conductivity of the feedstock was determined (K-System II) in accordance with ASTM D 5930. The initial temperature was 190°C and the final temperature was 30°C. The probe voltage was kept at 4 V with an acquisition time of 45 s. Figure 10 shows the variation of thermal conductivity with temperature for the feedstock. It was found that increasing the value of thermal conductivity by 10% resulted in more rapid filling of the mold, corresponding to a decrease in the total fill time by 20.1%, which in turn reflects a faster filling of the microchannels. Process Parameters The following process parameters were studied to analyze the microchannel-filling behavior: 1. Injection Speed An increase in the injection speed increased the amount of feedstock flowing into the microchannels. However, a lower injection speed would be preferred in order to avoid powder–binder separation. 2. Packing Pressure Different packing pressure profiles were evaluated using Moldflow to determine the effect of this process variable on feedstock flow into the microchannels. It was concluded that the pressure profiles did not affect the microchannels flow to any significant extent. 3. Melt Temperature A higher melt temperature resulted in faster feedstock flow into the microchannels. Figure 11 shows the effect of changing melt temperature on Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
filling of the microchannels, bulk, and complete fill of the μPIM part. Part Geometry To avoid defects such as incomplete mold filling, further studies were conducted on component geometry effects. The percentage of microchannel fill vs. bulk fill was quantified using Moldflow for different bulk thicknesses. Parts with various thicknesses relative to the bulk were studied using Moldflow. Decreasing the bulk thickness led to an increase in the amount of feedstock flow into the microchannels. A possible reason for this observation is that decreasing the bulk thickness increases the cavity pressure and forces the feedstock flowing into the microchannels. The feedstock was observed to move faster into the microchannels for thinner bulk sections, as shown in Figure 12.
Figure 12. Effect of bulk thicknesses on feedstock fill of microchannels
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CHARACTERIZATION AND SIMULATION OF MACROSCALE MOLD-FILLING DEFECTS IN MICROMINIATURE POWDER INJECTION MOLDING
TABLE III. RESULTS OF SENSITIVITY ANALYSIS Increase (or Decrease) in Total Mold-Filling Time (%) No. Property 1 2 3 4 5 6
Decreasing Experimental Value of Property by 10%
Increasing Experimental Value of Property by 10%
0.0 -20.3 -40.2 -19.9 -80.7 15.2%
20.1 0.0 20.1 20.1 0.2 -10.8%
Thermal Conductivity Specific Heat A1–WLF Temperature-Shift Factor Melt Temperature, 190°C Mold Temperature, 150°C Bulk Thickness of Part, 1.5mm
Sensitivity Analysis Each of the material parameters (viscosity, PVT, thermal conductivity, specific heat), processing parameters (melt and mold temperature), and part geometry were varied by ±10% from their experimental values to study their effect on the filling of the microchannels. The six primary parameters identified after this sensitivity analysis are given in Table III. Negative values in the table show the % increase in the mold-filling time of the experimental part, compared with the mold-filling time when the parameters are not changed. Positive values denote the % decrease in the total fill time of the cavity, compared with the mold-filling time when the parameters are not changed. Increasing the thermal conductivity by 10% appears to result in faster filling of the mold (a decrease in the total fill time by 20.1%), which in turn fills the microchannels faster. If the specific heat of the feedstocks is decreased by 10%, then the total fill time is observed to increase by 20.3%. This increase in total fill time leads to slower filling of the microchannels. Similarly, further decreasing the mold temperature below 150°C by 10%, increases the total fill time by 80.7%. This means
that the microchannels fill more slowly at 150°C. However, increasing the mold temperature by 10% above 150°C does not change the total fill time of the cavity. Similarly, the other parameters can be interpreted. A1 and melt temperature have a significant effect (decrease in the flow in the cavity or increase in the total fill time) by a decrease in their experimental value by 10%. However, if the bulk thickness of the part is decreased by 10%, flow in the microchannels increases rapidly by 15%. Table IV summarizes recommendations to make an effective MCA part based on the results of this study. Experimental validation of these observations using computer simulations is the focus of ongoing and future work. CONCLUSIONS Three parameters of the μPIM of MCAs minimize mold-filling defects, namely, material properties, processing parameters, and part geometry. • Material-Related Parameters: - Feedstock viscosity plays an important role. Newtonian behavior (power-law index, n ~ 1) is important for improved and faster filling of microchannels.
TABLE IV. RECOMMENDATIONS TO MINIMIZE DEFECTS IN MCAS Properties/Parameters/ No. Geometry
56
1
Thermal Conductivity
2
Specific Heat
3
Power-Law Index, n
4
Melt Temperature, 190°C
5
Mold Temperature, 150°C
6
Bulk Thickness of Part, 1.5 mm
Input (Increase or Decrease from Experimental Value)
Output (Flow in Microchannels as a Function of Fill Time)
Variable
Material Properties
Processing Parameters
Part Geometry Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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- Sensitivity analysis showed that the thermal conductivity, if increased by 10% of the experimental value, increases the flow of feedstock in the microchannels by ≥20%. - A decrease in the specific heat by 10% decreases the flow of feedstock into the microchannels by 20%, based on the sensitivity analysis. • Processing-Related Parameters: - Control of the melt temperature and mold temperature were the most crucial in avoiding defects. A higher melt temperature gives improved flow into the microchannels. Mold temperatures up to 150°C increase the flow of feedstock in the microchannels. Further increases in mold temperatures do not have any significant effect. - A high injection pressure and clamp force are required to produce MCAs. As a result, there is an increased tendency to form defects such as short shots, jetting, powder–binder separation, and flashing due to the sub-optimal selection of process parameters or feedstock material choice. • Design is important to molding success for MCA components: - A thinner bulk section is better for feedstock flow in the microchannels. - Any modifications in part design that will help to decrease the number of defects can be done using Moldflow Plastic Insight. An experimental understanding of mold-filling behavior and material-homogeneity issues and models for microsystem design significantly contribute to the technological foundation and future development of PIM for microscale applications. ACKNOWLEDGEMENT These data and observations are primarily based on research sponsored by Hewlett-Packard. Additional funding was provided by the Air Force Research Laboratory under agreement number FA8650-05-1-5041. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, by the Air Force Research Laboratory or the U.S. Government. REFERENCES 1. K.F. Ehmann, D. Bourell, M.L. Culpepper, T.J. Hodgson, T.R. Kurfess, M. Madou, K. Rajurkar and R.E. DeVor, “WTEC Panel Report on International Assessment of
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
2.
3.
4.
5. 6.
7.
8.
Research and Development in Micromanufacturing”, Micromanufacturing: International Assessment of Research and Development, 2005, Springer, Dordrecht, The Netherlands. R.S. Wegeng, M.K. Drost and D.L. Brenchley, “Compact Fuel Processors for Fuel Cell Powered Automobiles Based on Microchannel Technology”, Fuel Cells Bulletin, 2001, vol. 3, no. 28, pp. 8–13. R.M. German, Powder Injection Molding Design & Applications: User’s Guide, 2003, Innovative Material Solutions, State College, PA. R.M. German and A. Bose, Injection Molding of Metals and Ceramics, 1997, Metal Powder Industries Federation, Princeton, NJ. R.M. German, Powder Metallurgy Science, 2nd edition, 1994, Metal Powder Industries Federation, Princeton, NJ. R.A. Saravanan, L. Liew, V.M. Bright and R. Raj, “Integration of Ceramics Research with the Development of a Microsystem”, Journal American Ceramic Society, 2003, vol. 86, pp. 1,217–1,219. V. Piotter, L. Merz, R. Ruprecht and J. Hausselt, “Current Status of Micro Powder Injection Molding,” Materials Science Forum, 2003, vol. 426–432, pp. 4,233–4,238. V. Piotter, N. Holstein, K. Plewa, R. Ruprecht and J. Hausselt, “Replication of Micro Components by Different Variants of Injection Molding”, Microsystem Technologies, 2004, vol. 10, pp. 547–551.
Quality Parts? Tools! Quality
CAD + CAM = *CIT
*COMPUTER INTEGRATED TOOLING 220 Shore Drive Burr Ridge, IL 60527 TEL (630) 986-1815 FAX (630) 570-4866
[email protected]
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9. V. Piotter, T. Benzler, T. Hanemann, H. Woellmer, R. Ruprecht and J. Hausselt, “Innovative Molding Technologies for the Fabrication of Components for Microsystems”, Proceedings of SPIE—The International Society for Optical Engineering, 1999, vol. 3,680, no. 1, pp. 456–463. 10. V. Piotter, T. Gietzelt and L. Merz, “Micro Powder-Injection Moulding of Metals and Ceramics”, Sadhana—Academy Proceedings in Engineering Sciences, 2003, vol. 28, pp. 299–306. 11. Z.Y. Liu, N.H. Loh, S.B. Tor, K.A. Khor, Y. Murakoshi and R. Maeda, “Production of Micro Components by Micro Powder Injection Molding”, Journal of Materials Science Letters, 2001, vol. 20, no. 4, pp. 307–309. 12. L. Merz, S. Rath, V. Piotter, R. Ruprecht, J. RitzhauptKleissl and J. Hausselt, “Feedstock Development for Micro Powder Injection Molding”, Microsystem Technologies, 2002, vol. 8, pp. 129–132.
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13. E. Kim, Y. Xia and G.M. Whitesides, “Polymer Microstructures Formed by Moulding in Capillaries”, Nature, 1995, vol. 376, pp. 581–582. 14. J.L. Wilbur, E. Kim, Y. Xia and G.M. Whitesides, “Lithographic Molding: A Convenient Route to Structures with Sub-micrometer Dimensions”, Adv. Mater., 1995, vol. 7, pp. 649–656. 15. R. Urval, C.L. Wu, S.V. Atre, S.J. Park and R.M. German, “CAE-Based Process Design for Microfluidic Components”, Powder Injection Moulding International, 2007, vol. 1, no. 1, pp. 53–58. 16. C.L. Wu, S.G. Laddha, S.V. Atre, S. Lee, K.L. Simmons, S.J. Park, R.M. German and D. Whychell, “Microscale Heterogeneity in Powder Injection Molded Ceramic Microarrays”, Powder Injection Moulding International, 2008, vol. 2, no. 2, pp. 68–73. ijpm
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MPIF Standard 35 MATERIALS STANDARDS FOR PM SELF-LUBRICATING BEARINGS, 2010 Edition ISBN #: 978-0-9819496-3-5 ~ 28 pages
The first revision to the standard in over 10 years. The 2010 edition includes: NEW Material Section (data property table) Diffusion-Alloyed Iron-Bronze Bearings—FDCT-1802K Revised footnotes for Bronze Bearings and new footnote for the CTG-1004-K10 material Data-table-column heading revisions Data tables now listed in alphabetical order by material system Revised verbiage throughout the standard including a new section under EXPLANATORY NOTES on Oil Impregnation Efficiency ENGINEERING INFORMATION (Inch–Pound and SI Units)—Verbiage and data table modifications New edition includes a 2-part index displaying alphabetical listings & guides to material systems and designation codes used in MPIF Standard 35 • Part 1: for the MPIF Standard 35, Materials Standards for PM Self-Lubricating Bearings document • Part 2: for the other MPIF Standard 35 publications METAL POWDER INDUSTRIES FEDERATION 105 College Road East, Princeton, NJ 08540-6692 Phone: (609) 945-0009 Fax: (609) 987-8523 Order Online: www.mpif.org
The U.S. Department of Commerce has identified PM as one of the nation’s “growth” technologies capable of enhancing the productivity of America’s manufacturing community. The Center for Powder Metallurgy Technology was founded in 1980 in order to foster the growth and vitality of PM. Since its inception as a “non-profit, cooperative technology foundation,” CPMT has been advancing PM technology through the collaborative research efforts of its member organizations: end users, parts fabricators, powder producers, and equipment & service providers. In addition, CPMT provides funding to academic institutions and students to help meet the industry’s need for scientifically trained personnel. Learn more about CPMT and its research projects and educational efforts at www.cpmtweb.org.
cpmtweb.org FOSTERING RESEARCH AND EDUCATION IN SUPPORT OF PM’S FUTURE Celebrating 30 years in R&D ~ Join us today
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MICROMINIATURE POWDER INJECTION MOLDING—PART II
SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION Xiangji Kong*, Thierry Barriere**, Jean-Claude Gelin** and Cédric Quinard**
INTRODUCTION μPIM is a key technology in the manufacture of microcomponents to generate microstructured surfaces.1 Due to the increasing demands in different fields of application, such as sensors and medical devices2, this process opens up a wide variety of markets with possible sustained growth. μPIM involves four stages: feedstock production by mixing of fine metallic powders and thermoplastic binders; injection of powder/ binder mixtures in the mold microcavity; thermal/catalytic or solvent debinding; and sintering by solid-state diffusion.1 The availability of commercial feedstock with fine powders is limited. 316L stainless steel gas-atomized prealloyed powder (D50 = 3.4 μm) was selected in our study since the sintered strength using the prealloyed powder is higher than that achieved using a master alloy.3 Currently there are many choices for the binder and it is important (but difficult) to select an appropriate one. In our case, a multicomponent system composed of a primary binder, a secondary binder, and a surfactant has been selected. Both monoinjection and bimaterial injection were attempted with the optimal feedstock. The binder is used as a fluid to carry the powder particles to the mold cavities in injection molding, so that in the debinding stage the binder becomes disposable. The determination of the debinding cycle is important in order to fully control the evolution of the component shape. After debinding, the focus shifts to the sintering stage involving solidstate diffusion in which the component shrinks to the required dimensions. The shrinkage must be isotropic to ensure that the required final geometry of the component can be achieved. Different models have been proposed for the simulation of sintering.
Adapted from powder injection molding (PIM), microminature powder injection molding (μPIM) technology meets the increasing demands for smaller parts and miniaturization. Research in this area has focused on 316L stainless steel powders with a D50 of 3.4 μm and polymer binders. Formulations with different binders have been evaluated in order to optimize the process. Rheological characterization of the feedstock was performed utilizing the selected powder and polymers from the selected formulations. Tensile and bend specimens were manufactured from the formulations with different powder loading contents. The μPIM equipment used was capable of processing either one or two different materials since it comprised two injection devices. Thus different bimaterial microcomponents have been fabricated and characterized in terms of part geometry and physical properties. Viscosity and shrinkage during sintering of the feedstock have been measured for different powder loadings and process kinetics. Useful behavior-law parameters have been determined in order to develop numerical sintering simulations by means of this finite element method (FEM).
*PhD Student, **Professor, FEMTO-ST Institute, Applied Mechanics Department, 24 rue de l’Epitaphe, 25000 Besançon, France; E-mail:
[email protected]
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
TABLE I. CHARACTERISTICS OF 316 L STAINLESS STEEL POWDER Powder Size and Density Powder
Size
D10
D50
D90
Density
316L Low Ni—Osprey
5 μm
1.8 μm
3.4 μm
6.0 μm
7.9 g/cm3
Powder Chemical Composition Element
Cr
Ni
Mo
Mn
Si
C
P
S
Fe
Content (w/o)
17.4
10.9
2.5
1.2
1.64
0.021
0.015
0.006
Bal.
A thermo-viscoplastic model has been utilized in our study. Before application of the finite element model to predict shrinkage and density during and after the sintering stage, several parameters have to be identified: feedstock formulation, powder, and selection of feedstock formulation. Feedstock Formulation Design of the feedstock formulation depends on numerous factors, such as mixture fluidity, feedstock homogeneity, adequacy of the debinding process, and debinding time. Thus, the choice of binder and its proportions should be thoroughly investigated before finalizing the mixtures. For example, Omar et al.4 have investigated the debinding stage for 316L stainless steel feedstock composed of polyethylene glycol (PEG), but this binder is better suited to solvent debinding. Binders based on polypropylene (PP), paraffin wax (PW), and stearic acid (SA) are compatible with thermal debinding. Powder At present, 316L stainless steel is a frequently used alloy in PIM because of its ability to sinter to high densities, accompanied by corrosion resistance.3 Imbaby et al.2 have studied the manufacturing of microparts with 316L stainless steel powders (D50 = 1.8 μm). Liu et al.5 have carried out analyses on mixing and characterization for micropowder injection molding with 316L stainless steel feedstock (D50 = 2.37 μm). Barriere et al.6 used a commercial 316L stainless steel feedstock (16 μm) for injection and sintering simulations. Quinard et al.7 have investigated the development and identification of 316L stainless steel feedstock loaded at 60 v/o (D50 = 5 μm and 16 μm). Recently spherical 316L stainless steel powders (D50 = 3.4 μm) were selected to prepare new feedstocks. Table I cites the powder-size distribution and the chemical composition. Figure 1 is a representative scanning electron micrograph (SEM) of this powder.
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Selection of Feedstock Formulation Different feedstocks with the same 316L stainless steel powder (D50 = 3.4 μm, loaded at 60 v/o), but with different binders and proportions were tested for maximal fluidity. Results of the characterization of the binders and formulations are given in Table II. The primary polymer binder PP was used to retain component shape after injec-
Figure 1. Representative images of 316L stainless steel powder (D50 = 3.4 μm). SEM Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
TABLE II. (a) CHARACTERIZATION OF BINDERS, (b) CONSTITUENTS AND FEEDSTOCK CONTENT Binder Type Designation Melting Temperature Degradation Temperature (°C) (°C) 1 1 2 3 3
Primary Primary Secondary Surfactant Surfactant
Polypropylene (PP) Polyethylene (PE) Paraffin Wax (PW) Stearic Acid (SA) Oleic Acid (OA)
140 130 58–60 70.1 16.7
400 400 300 395 350
Density g/cm3 0.90 0.91 0.91 0.94 0.91 (a)
Formulation Type 1 v/o w/o
Powder Stainless Steel 316L 60 92.90
Primary Binder PE 16 2.90
Secondary Binder PW 24 4.20
Surfactant -
2
Type v/o w/o
Stainless Steel 316L 60 92.90
PP 16 2.80
PW 22 3.90
SA 2 0.40
3
Type v/o w/o
Stainless Steel 316L 60 92.81
PE 38 6.84
-
OA 2 0.35 (b)
tion molding and debinding. The main effect of the secondary polymer binder PW was to decrease the feedstock viscosity and increase the replicating ability of the feedstock. The surfactant SA was used to facilitate powder wetting.5 The feedstock quality varied significantly with the properties of the binder, so it was necessary to determine the appropriate one. Three different mixtures were prepared at 160°C in a twin-screw mixer. The measured mixing torques are given in Figure 2(a); the final mixing torque corresponding to formulation 2 is about 0.3 N·m, compared with 16 N·m and 5 N·m for formulations 1 and 3, respectively. Formulation 2 gives the lowest torque and stabilizes more rapidly than the two others. The viscosities of the three feedstocks are given in Figure 2(b). Formulation 2 (PP + PW + SA) exhibits the smallest shear viscosity. From SEMs (Figure 3) of both feedstocks developed according to formulation 2, it is seen that the stainless steel powder particles are uniformly distributed between the binders. Thus, this formulation was utilized in the subsequent tests. DETERMINATION OF CRITICAL POWDER LOADING General Aspects of Critical Powder Loading In PIM, a higher level of powder loading is beneficial in relation to the resulting properties of the component. However, the powder loading cannot be increased without limit.8 Too high a powder Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Figure 2. (a) Mixing torque as a function of time for three feedstocks (powder loading 60 v/o), (b) shear viscosity as a function of shear rate for three feedstocks (powder loading 60 v/o)
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Mixing Tests: Continuously Increasing Powder Loading For the first test, the powder loading was gradually increased from 50 v/o to 78 v/o by adding the powder in increments of 2 v/o. This methodology has also been used by Jardiel et al.9 due to its simplicity in determining the critical solids loading using only one test cycle. The mixing torque as a function of powder loading is shown in Figure 4(a). There are three different zones on the curve. In zone 1, there is mainly binder in the mixture and the torque remains at a low level. In zone 2 the torque increases at ~64 v/o, whereas in zone 3 the torque increase rapidly for powder loadings in the range 70 v/o to 78 v/o. Thus, from this incremental test, the critical solids loading has been fixed between 64 v/o and 70 v/o. However, this complete cycle takes about 225 min (including 14 sequential increases in powder content) with intensive shearing that leads to decomposition of the stearic acid. In order to ensure that the final quantity of the
Figure 3. Representative images of feedstock after mixing, formulation 2. (a) 60 v/o powder loading, and (b) 66 v/o powder loading. Mixing temperature 160°C, mixing rotational speed 30 rpm, mixing time 30 min. SEM
content means there is not sufficient binder to fill out the desired geometry with the powder particles. Four different methods were compared in this work. The first two consisted of mixing tests carried out with a continuously increasing powder loading or by incrementally increasing the powder loading in the two-screw mixer using the same conditions as those in the tests to select the feedstock formulation, but with different powder weight. In order to determine the power law for characterizing rheological behavior, a capillary rheometer was used to measure the viscosities of the different feedstocks at 160°C with shear rates from 192 s-1 to 10000 s-1. The capillary die had an orifice 1 mm dia. and a length of 16 mm.
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Figure 4. Mixing torque as a function of powder loading (formulation PP + PW + SA, mixing temperature 160°C, rotational-mixing speed 30 rpm, mixing time 30 min): (a) continuously increasing powder loading, (b) incrementally increasing powder loading
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feedstock will not exceed the maximal content of the mixer, 70 g (about 25% of the maximal content of the mixer of powder) were added to the mixer cavity at the beginning of the test. Thus, the mixing torques (Figure 4(a)) are lower than those in the next test for the same powder loading (especially for loadings <66 v/o). This is because more powder (160 g) is involved in the subsequent test. Mixing Tests: Incremental Increases in Powder Loading Since the critical powder loading was fixed between 64 v/o and 70 v/o, mixtures were prepared one by one (instead of increasing continuously) with powder loadings from 60 v/o to 78 v/o (instead of from 50 v/o to 78 v/o in the first test). Figure 4(b) shows that from 60 v/o to 64 v/o powder loading, the torque remains essentially stable; it begins to increase slowly above 64 v/o. Above 70 v/o, the torque increases rapidly since there in insufficient binder to promote mixing. Thus, the critical powder loading is located in the range of 64 v/o to 70 v/o as in the first test.
viscosities are related in Figure 6(a) corresponding to equation (1). The power-law exponent (n) is plotted in Figure 6(b), as a function of the powder loading. It provides the way to determine a critical pow-
Figure 5. Shear viscosities as a function of shear rate and powder loading for formulation 2 (PP + PW + SA) feedstock
Rheological Tests Feedstocks loading levels from 60 v/o to 72 v/o were tested sequentially for viscosity using a capillary rheometer at 160°C, Figure 5. From 60 v/o to 66 v/o the viscosities vary slowly, but in zone 2 they start to increase progressively; above 70 v/o, an abrupt rise in seen (zone 3). From these rheological measurements, the critical powder loading is located in the range of 66 v/o to 70 v/o. In addition, the viscosities of the feedstocks corresponding to formulation 2 are always <180 Pa·s and these feedstocks are suitable for injection molding. Power-Law Model Tests From the previous tests, the critical powder loading was fixed at 66 v/o to 70 v/o. A complementary test was conducted to more accurately define the critical powder loading, based on the previous rheological results. This approach has been proposed by Aggarwal et al.10 in which the viscosity is expressed by a simple power-law model which includes the effect of temperature:11,12
[ ]
E γ⋅ n–1 (1) η(γ⋅ ,T ) = B exp –––– RT where η, γ⋅ , n, B, E, and R correspond to viscosity, shear rate, the power-law exponent, a material specific reference factor, the flow activation energy for the Arrhenius temperature dependence of the viscosity, and the gas constant, respectively. The Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Figure 6. (a) shear viscosity (power-law model) as a function of shear rate for formulation 2 (PP + PW + SA) feedstock, (b) power-law exponent (n) as a function of powder loading for formulation 2 (PP + PW + SA) feedstock
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der loading zone corresponding to the minimal value of the exponent; thus, 68 v/o has been retained for the critical powder volume solids loading. Based on our tests, the critical solids loading for 316L stainless steel powder (D50 = 3.4 μm) was identified as 68 v/o. INJECTION MOLDING TESTS Equipment Dedicated equipment has been developed for μPIM embracing electric injection molding and systems to check the quality of the components.13,14 The
microinjection Battenfeld Microsystem© 50 is adapted for microparts with weights as low as 0.1 mg. Mold Design and Manufacturing Since the molds are specifically used for μPIM, equipment such as laser micromanufacturing, high-speed micromilling (HSM), and microwire electrical discharge machine(WEDM) have been used to manufacture the molds.15 The microinjection two-plate mold used for tensile and beambending specimens is shown in Figure 7(a); the configuration of the beam-bending specimen is given in Figure 7(b).
Figure 7. Microinjection two-plate molds: (a) micro-monoinjection of tensile specimen and beam-bending specimen, (b) micro bimaterial injection of beam-bending specimen
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
Bimaterial Injection It is widely recognized that the two materials in bimaterial injection molding need to exhibit similar magnitudes of thermal expansion, sintering kinetics, and bonding characteristics.16 Both feedstocks in this test were prepared from the same powder (D50 = 3.4 μm) and the same wax–polymer binder (formulation 2). One feedstock was loaded at 60 v/o and the other feedstocks were loaded at 62 v/o, 64 v/o, and 66 v/o, respectively. After granulating the feedstock bulk into small pieces to facilitate injection, the feedstocks were successfully injected at 220°C. The interface between the two feedstocks was not straight, and its position varied with the injection parameters, Figure 8(c). Accordingly, another mold specially designed for bimaterial injection molding with two separated injection chambers will be developed in the future.
Debinding In the debinding stage, much of the binder in the molded component is removed in the shortest possible time by employing solvent, catalyst, or other techniques that limit the influence of the debinding component.17 In our laboratory, the thermal debinding process has been established with emphasis on simplicity, safety, and minimal environmental impact. In the debinding cycle, the chemical composition of the binders is critical. For the wax–polymer binder, a standard thermal-debinding cycle was utilized in a nitrogen atmosphere. The debinding oven was heated at a ramp speed of 0.1°C/min from ambient temperature to 130°C, which is below the melting temperature of the backbone polypropylene. Then the temperature was increased to 220°C at a heating rate of 0.075°C/min, followed by holding for 120 min at
Figure 8. (a) Beam-bending specimen injected using feedstock loaded at 60 v/o and 64 v/o; formulation 2 (PP + PW + SA), (b) beam-bending specimens injected with two feedstocks (60 v/o for one half and 64 v/o for the other half) after injection, debinding, and sintering Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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this temperature. The components were then cooled over 120 min to ambient temperature. Following this debinding cycle, ~75% of the binders were removed resulting in open pores in the component. The resulting debound components were free of defects such as uneven binder removal, Figure 8(b). The initial shape of the injected components was retained in the porous parts, so that there was only a small dimension change between the injected and the debound specimens. SINTERING TESTS Sintering Stage The purpose of the sintering stage is to bond the metal particles together by solid-state diffusion in order to form a homogenous structure when full densification is achieved.18 The pores inside the debindered components are eliminated in this stage and the components exhibit excellent strength, with properties that are often superior to those resulting from other processes. In the present study, the porous debound material was heated to 1,360°C (slightly lower than the melting point of the 316L stainless steel powders) to activate rapid sintering. Previous investigations19–21 have shown that the primary parameters in the sintering cycle are: heating rate, sintering time, sintering temperature, and sintering atmosphere.20 In some situations, the pores will coarsen due to expansion of the gas in the pores when the sintering is carried out at a high temperature.22 Furnace Sintering Specimens prepared from bimaterial injection have been sintered in vacuum to avoid expansion from the gas in the pores. Different heating rates were evaluated in order to analyze their influence on sintering since the sintering time depends on the heating rate. First the debound components were heated from ambient temperature to 600°C over a 120 min interval, then the temperature was maintained for 30 min, after which the components were heated to 1,360°C at a heating rate of 10°C/min and kept at 1,360°C for 120 min. Finally, cooling at a rate of 10°C/min was applied. This resulted in correctly sintered components, as shown in Figure 8(b), with no obvious faults and no cracks near the interface between the two different feedstocks. Over 12 v/o shrinkage occurred in the components injected with the two feedstocks loaded at 60 v/o and 64 v/o, respectively.
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PHYSICAL AND NUMERICAL MODELING OF SINTERING STAGE Purpose In sintering a rapid heating rate can induce various defects in the sintered components; these include cracks and distortion due to stress and temperature gradients.23 Instead of performing numerous sintering experiments, numerical simulation by the FEM has been proposed to estimate shrinkage, relative density, and variation in the shape of microcomponents during and after sintering.23 Evolution of Constitutive Law With some simplification of the sintering process, various models have been developed.24 Among these models, the phenomenological model based on continuum mechanics uses the FEM to predict the dimensional change in components during the sintering stage.25 Under high-sinteringtemperature conditions, the macroscopic behavior of the material can be simulated as creep deformation.26–28 Thus, the solid-state sintering is described by means of a thermo-elasto-viscoplastic constitutive law, expressed as:23 σ′ tr (σ) – 3σs ε⋅vp = –––– + ––––––––––– I (2) 2Gp 9Kp where ε⋅vp is the viscoplastic strain rate, σ′ is the deviatoric stress tensor, tr (σ) is the trace of the stress tensor, I is the second-order identity tensor, Gp is the shear-viscosity modulus Kp is the bulkviscosity modulus, and σs is the sintering stress. Gp, Kp, and σs refer to the material parameters to be determined. The elastic-viscous analogy is used to define the shear- and bulk-viscosity moduli in the sintering of materials:27 ηp ηp Gp = ––––––––– , Kp = ––––––––– 3(1 – 2vp) 2(1 + vp)
(3)
where ηp and vp are the uniaxial viscosity and the viscous Poisson’s ratio of the porous material. Song et al.23 have defined the following relationship to define the uniaxial viscosity ηPe in the tests:
(
)
PL3s 1 5ρagL4s ηPe = ––– + –––––– (4) ·δ ––––––– 2 32h 4bh3 · where δ is the deflection rate at the center of the specimen, ρa is the apparent density, g is gravity, P is the external load, and Ls, b, and h are respectively the distance between the two supporting rods and the width and thickness of the speciVolume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
men.23 The viscous Poisson’s ratio is determined by the relation:27 –––––––––– ρ (5) vP ≈ –––––––– 3–2ρ
√
where ρ is the relative density which can be calculated by means of expression: ρ0 ρ = ––––––– (1 + λ)3
(6)
where ρ0 is the relative density after presintering and λ is the uniaxial shrinkage defined as: L – L0 λ = ––––––– L0
(7)
where L0 and L refer to the length of the specimen
before and after sintering. The following equation is proposed to determine the sintering stress:29 σs = BρC
(8)
where B and C are the material parameters identified from dilatometric experiments. From the conservation equation, the related parameters can be determined. IDENTIFICATION OF SINTERING PARAMETERS Dilatometric Tests A vertical dilatometer (Figure 9(a)) equipped with probes was used to carry out the identification analysis. Both the beam bending tests and the free sintering tests were carried out to determine δ (equation (4)) and λ (equation (6)). Similar tests
Figure 9. (a) Vertical dilatometer used for beam-bending tests and free-sintering tests in vacuum, (b) set up for beam-bending experiments in vertical dilatometer showing geometry of sintering support, (c) set-up for presintering of cylindrical powder specimen in dilatometer Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
were performed previously in a horizontal dilatometer for feedstocks loaded at 60 v/o.7 The present tests were carried out on the feedstocks with higher loading, namely, 62 v/o, 64 v/o, and 66 v/o. Beam-Bending Tests The beam-bending test was used to identify the viscosity of the sintered parts at high temperature.31 The confirmation is illustrated in Figure 9(b). The distance between the two knife edges of the supporting base was 12 mm, and rectangular specimens 14 mm (length) × 5.5 mm (width) × 1 mm (thickness) were prepared for the tests. A load equal to 5 cN was applied at the center of the specimen via a rod. Three different rates were used to heat the specimens up to 1,360°C: 5°C/min, 10°C/min, and 15°C/min in vacuum. After the heating ramp, a holding time of 120 min was imposed to reduce the level of porosity in the specimen. The specimens were then cooled to ambient temperature at a rate of 10°C/min in order to achieve significant densification and the desired microstructure in the sintered components.
the binder, and the particle size of the powder. 2) The powder materials begin to flow when the temperature is >1,000°C, which is in agreement with results obtained by different authors. 3) The feedstocks exhibit higher uniaxial viscosities at a lower heating rate of 5°C/min. For the feedstock loaded at 62 v/o, the uniaxial viscosity exhibits an abrupt increase at ~1,225°C at a heating rate of 15°C/min. This behavior is not predict-
RESULTS AND DISCUSSION Beam Bending Due to the small magnitude of the defections, the influence of gravity was ignored and equation (1) can be simplified to: 1 PL 3s η Pe = –– –––––– δ˙ 4bh3
(9)
Based on equation (9), the uniaxial viscosities were calculated and plotted as a function of sintering temperature and powder loading in Figure 10. Based on the results obtained from these tests, the following conclusions can be drawn: 1) The uniaxial viscosities are in the range of 0.1–0.3 GPa·s for 316L stainless steel powders. Blaine30 obtained values of uniaxial viscosity in the range of 0.2–0.6 GPa·s for 316L stainless steel powders compacted with boron. Lame31 reported values of uniaxial viscosity in the range of 60–80 GPa·s for iron powder compacts. Vagnon32 reported a uniaxial viscosity for 316L stainless steel powder compacts in the range of 4–50 GPa·s. In our laboratory, Song23 determined values of uniaxial viscosity in the range of 8–10 GPa·s. The differences between the results reported by Blaine30 and Lame31 can be explained primarily in terms of the homogeneity of the feedstock, the content of
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Figure 10. Uniaxial viscosity ηPe (equation (8)) as a function of temperature from beam-bending tests, 316 L stainless steel powders, D50 = 3.4 μm, vacuum. (a) 62 v/o powder loading, (b) 64 v/o powder loading, (c) 66 v/o powder loading Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
ed and additional tests should be preformed to explain/understand this observation. 4) At the same heating rate, the higher the feedstock is loaded, the higher is the uniaxial viscosity at the same temperature. This is related to the fact that the higher the powder loading, the higher is the feedstock viscosity.
Figure 11. Uniaxial shrinkage λ (equation (6)) as a function of temperature in free sintering. 316 L stainless steel powders, D50 = 3.4 μm, vacuum: (a) 62 v/o powder loading, (b) 64 v/o powder loading, (c) 66 v/o powder loading
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
Free Sintering In order to characterize the shrinkage behavior of the sintered components, sintering tests were performed using the same sintering cycle as in the beam-bending tests but without any applied force on the specimen. The end of the rod and the base were flat (Figure 9(c)). Cylindrical specimens 10 mm (length) × 5 mm (dia.) were prepared for these tests. Due to possible distortion and fragility, the cylindrical specimens were presintered. They were heated to 700°C at 10°C/min. After a 120 min holding time the specimens were cooled to ambient temperature at 10°C/min in vacuum. This thermal cycle improved the mechanical properties of the presintered specimens. Shrinkage as a function of sintering temperature in the free sintering tests conducted in vacuum is shown in Figure 11. The following conclusions can be drawn from these experiments: 1) Shrinkage begins at ~1,000°C; at >1,050°C it increases rapidly up to ~1,200°C. Above this temperature and up to 1,360°C shrinkage largely decreases. 2) At the same temperature, a large shrinkages occurs in specimens with a lower powder loading. This is related to the fact that when powder loading is important, more pores are produced, so after sintering the components shrink more. 3) A higher density was obtained using a lower heating rate since greater shrinkage occurred. For the feedstock loaded at 64 v/o, by heating at 5°C/min, 10°C/min, and 15°C/min, the densities of the sintered specimens were 7.618 g/cm3, 7.593 g/cm3, and 7.567 g/cm3, with attendant shrinkage levels of 12.51%, 12.26% and 12.20%, respectively. The increase in density, consistent with the drop in heating rate, is evident. In comparison with the lower heating rate, less time is available for the components to shrink during sintering under rapid heating. CONCLUSIONS AND PERSPECTIVES This contribution summarizes the results of an experimental investigation of the sintering of components obtained by the μPIM of 316L stainless steel. The feedstock based on 316L stainless steel micropowders with different polymers can be readily decomposed by thermal debinding. Approaches to determine the critical powder content are discussed, and the approximate powder loading window is selected. Debinding cycles are proposed that are compatible with μPIM. Sintering tests were investigated with the objective of determining the correct sintering cycle resulting in
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SINTERING OF POWDER INJECTION MOLDED 316L STAINLESS STEEL: EXPERIMENTAL INVESTIGATION AND SIMULATION
components with the desired geometry and mechanical properties. An identification procedure is proposed to determine the kinetics of the viscous behavior associated with isotropic sintering. The results indicate that a lower shrinkage is obtained with high powder loadings. REFERENCES 1. R.M. German and A. Bose, Injection Molding of Metals and Ceramics, 1997, Metal Powder Industries Federation, Princeton, NJ. 2. M. Imbaby, K. Jiang and I. Chang, “Fabrication of 316-L Stainless Steel Micro Parts by Softlithography and Powder Metallurgy”, Materials Letters, 2008, vol. 62, pp. 4,213–4,216. 3. D.F. Heaney, T.J. Mueller and P.A. Davies, “Mechanical Properties of Metal Injection Moulded 316L Stainless Steel Using Both Prealloy and Master Alloy Techniques”, Powder Metallurgy, 2004, vol. 47, no. 4, pp. 367–373. 4. M.A. Omar, R. Ibrahim, M.I. Sidik, M. Mustapha and M. Mohamad, “Rapid Debinding of 316L Stainless Steel Injection Moulded Component”, Journal of Materials Processing Technology, 2003, vol. 140, pp. 397–400. 5. L. Liu, N.H. Loh, B.Y. Tay, S.B. Tor, Y. Murakoshi and R. Maeda, “Mixing and Characterization of 316L Stainless Steel Feedstock for Micro Powder Injection Molding”, Materials Characterization, 2005, vol. 54, pp. 230–238. 6. T. Barriere, J.C. Gelin and B. Liu, “Experimental and Numerical Investigations on Properties and Quality of Parts Produced by MIM”, Powder Metallurgy, 2001, vol. 44, no. 3, pp. 228–234. 7. C. Quinard, T. Barriere and J.C. Gelin, “Development and Property Identification of 316L Stainless Steel Feedstock for PIM and μPIM”, Powder Technology, 2009, vol. 190, pp. 123–128. 8. Y. Li, L. Li and K.A. Khalil, “Effect of Powder Loading on Metal Injection Molding Stainless Steels”, Journal of Materials Processing Technology, 2007, vol. 183, pp. 432–439. 9. T. Jardiel, M.E. Sotomayor, B. Levenfeld and A. Várez, “Optimization of the Processing of 8-YSZ Powder by Powder Injection Molding for SOFC Electrolytes”, International Journal of Applied Ceramic Technology, 2008, vol. 5, no. 6, pp. 574–581. 10. G. Aggarwal, S.J. Park and I. Smid, “Development of Niobium Powder Injection Molding: Part I. Feedstock and Injection Molding”, International Journal of Refractory Metals & Hard Materials, 2006, vol. 24, pp. 253–262. 11. Y. Li, B. Huang and X. Qu, “Viscosity and Melt Rheology of Metal Injection Molding Feedstocks”, Powder Metall. 1999, vol. 42, no. 1, pp.86–90. 12. X. Chen, Y.C. Lam, Z.Y. Wang and K.W. Tan, “Determination of Phenomenological Constant of ShearInduced Particle Migration Model”, Comput. Mater. Sci., 2004, vol.30, pp. 223–229. 13. C.G. Kukla, “Micro Injection Molding”, Int. J. of Forming Processes 4, 2001, vol. 3–4, pp. 253–269. 14. A.C. Rota, F. Petzoldt and P. Imgrund, “Micromolding of Advanced Material Combinations”, Proc. Int. Conf. on Powder Injection Molding of Metals, Ceramics & Carbides, edited by R.M. German, The Pennsylvania State Univ.,
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State College, PA, 2003, pp. 1–18. 15. J.C. Gelin, T. Barriere and B. Liu, “Mould Design Methods by Experiment and Numerical Simulation in Metal Injection Molding”, J. of Engineering Manufacture, 2002, vol. 126, part B, pp. 1,533–1,547. 16. D.F. Heaney, P. Suri and R.M. German, “Defect-Free Sintering of Two Material Powder Injection Molded Components”, Journal of Materials Science, 2003, vol. 38, pp. 4,869–4,874. 17. J. Song, T. Barriere, J.C. Gelin and B. Liu, “Powder Injection Molding of Metallic and Ceramic Hip Implants”, Int. J. Powder Metall., 2009, vol. 45, no. 3, pp. 25–34. 18. R.M. German, Sintering Theory and Practice, 1996, J. Wiley and Sons, New York, NY. 19. H.S. Nayar and B. Wasiczko, “Nitrogen Absorption Control During Sintering of Stainless Steel Parts”, Metal Powder Report, 1990, vol. 45, no. 9, pp. 611–614. 20. L. Cai and R.M. German, “Powder Injection Molding Using Water Atomized 316L Stainless Steel”, Int. J. of Powder Metall., 1995, vol. 31, no. 3, pp. 257–264. 21. J. Rawers, F. Croydon, R. Krabbe and N. Duttlinger, “Tensile Characteristics of Nitrogen Enhanced Powder Injection Moulded 316L Stainless Steel”, Powder Metall., 1996, vol. 39, no. 2, pp. 125–129. 22. R.M. German, Powder Injection Molding, 1990, Metal Powder Industries Federation, Princeton, NJ. 23. J. Song, T. Barriere, B. Liu, J.C. Gelin and M. Gerard, “Experimental and Numerical Analysis on Sintering Behaviours of Injection Moulded Components in 316L Stainless Steel Powders ”, Powder Metallurgy, 2008 in press. 24. R.M. German, “Computer Modeling of Sintering Processes”, Int. J. Powder Metall., 2002, vol. 38, no. 2, pp. 48–66. 25. E. Olevsky, “Theory of Sintering: From Discrete to Continuum”, Mater. Sci. Eng., 1998, vol. R23, pp. 41–100. 26. R.L. Coble, “A Model for Boundary Diffusion Controlled Creep in Polycrystalline Materials”, J. Appl. Phys., 1963, vol. 34, no. 6, pp. 1,679–1,682. 27. R.K. Bordia and G.W. Scherer, “On Constrained Sintering-I Constitutive Model for a Sintering Body”, Acta Materialia, 1988, vol. 36, no. 9, pp. 2,393–2,397. 28. F.R.N. Nabarro, “Creep at Very Low Rates”, Metall. Mater. Trans. A., 2002, vol. 33A, no. 153, pp. 213–218. 29. A. Peterson and J. Agren, “Constitutive Behavior of WCCo Materials with Different Grain Size Sintered Under Load”, Acta Materialia, 2004, vol. 52, pp. 1,847–1,858. 30. D.C. Blaine, R. Bollina, S.J. Park and R.M. German, “Critical Use of Video-Imaging to Rationalize Computer Sintering Simulation”, Computers in Industry, 2005, vol. 56, no. 9, pp. 867–875. 31. O. Lame, D. Bouvard and H. Wiedemann, “Anisotropic Shrinkage Gravity Induced Creep During Sintering of Steel Powder Compacts”, Powder Metall., 2002, vol. 45, no. 2, pp. 181–185. 32. A. Vagnon, D. Bouvard and G. Kapelski, “An Anisotropic Constitutive Model for Simulating the Sintering of Stainless Steel Powders Compacts”, Technology & Applications of Sintering, Proceedings of the 4th International Conference on the Science of Sintering, Grenoble, France, 2005, pp. 232–235. ijpm
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PM INDUSTRY NEWS IN REVIEW The following items have appeared in PM Newsbytes since the previous issue of the Journal. To read a fuller treatment of any of these items, go to www.apmiinternational.org, login to the “Members Only” section, and click on “Expanded Stories from PM Newsbytes.”
Ecka Restructures U.S. Operations In conjunction with restructuring its copper and aluminum divisions in the U.S., Ecka Granulate Velden GmbH, Germany, has appointed EA Metal Powders, LLC, Columbia, S.C., as exclusive sales agent in North America for copper and copper-alloy powders. The new agency company is owned by Nic Veloff, former general manager of sales and technical support of Ecka Granules of America LLC. New Distributor for SinteredFilter Powder TWO H Chem Ltd., Chungcheonbuk, Korea, has retained PolyGroup Inc., Cincinnati, Ohio, as exclusive distributor of specialized polymers in North America. Its product line includes fine polyethylene powders used as a sintering agent in the production of PM stainless steel and bronze filters. GKN PM Businesses Recovering GKN Plc, London, expects its automotive and powder metallurgy businesses to make strong progress in 2010 after a disappointing 2009 when PM sales declined 27 percent to £512 million (about $773 million). PM sales fell sharply in Europe and North America but improved in Asia and South America, supported by a strong second half in India, China, and Brazil. Catalyst Business Sold H.C. Starck, Goslar, Germany, has sold its AMPERKAT catalyst busiVolume 46, Issue 3, 2010 International Journal of Powder Metallurgy
ness to Evonik Degussa GmbH, Essen, Germany. The product line includes activated nickel sponge catalysts and customized catalysts used in the pharmaceutical, food, and fine-chemicals industries. Copper-Powder Plant Resumes Production Improving business conditions have led ACuPowder International LLC, Union, N.J., to resume production at its water-atomized copper-powder plant in Greenback, Tenn., reports Edul M. Daver, president. In response to a decrease in demand in 2009, the company had consolidated atomized-copper-powder production to the company’s main plant in Union, N.J. New Part-Handling Trays Molded Fiber Glass Tray Company, Linesville, Pa., has introduced a new line of highstrength glass-reinforced thermoplastic trays designed for the PM parts-manufacturing process. The trays handle, move, and store PM parts in both pre- and post-sintering operations, including automated and manual handling. Cloyes Sells Rush Metals Cloyes Gear and Products Inc., Forth Smith, Ark., sold its Rush Metals PM parts subsidiary in Billings, Okla., to Melling Engine Parts on March 12. Rush, which has been in business for 45 years making PM gears, sprockets, cams, pulleys, and washers, had been acquired by Cloyes in 1980.
New Powder Metallurgy Directory Inovar Communications Ltd., Shrewsbury, England, has published the 14th edition of the 504-page International Powder Metallurgy Directory 2010–2011. It contains 4,800 entries covering metal powder and equipment suppliers, and companies supplying traditional PM parts, metal injection molding (MIM) parts, hardmaterials/cemented carbides, diamond tools, sintered magnets, and other products and services. German Government Funds Research on Superconductive Tungsten Wire The Ministry of Economic Affairs and Energy of Germany’s federal state of North Rhine-Westphalia is providing 860,000 euros (about $1.15 million) to study methods for manufacturing low-cost superconductive nickel–tungsten wire for wind-power generators, reports ChemEurope.com. Zenergy Power GmbH will collaborate with ThyssenKrupp VDM and three other research partners. Positive MIM Market Outlook Most members (77 percent) of the Metal Injection Molding Association (MIMA) forecast continued growth this year, according to a report by Matt Bulger, MIMA president, to be given at the International Conference on Injection Molding of Metals, Ceramics and Carbides held [March 29–31] in Long Beach, California. The conference has attracted 120 participants from 17 countries.
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PM INDUSTRY NEWS
Titanium Powder Plant Planned International Titanium Powder LLC, Woodbridge, Ill., will begin producing commercial quantities of pure and prealloyed titanium powders later this year at a new plant in Ottawa, Ill., according to . The plant is reported to have an annual capacity of four million pounds when fully operational. New Plant to Meet Growing Demand for PM Fuel-Cell Plates Plansee High Performance Materials, Reutte, Austria, has announced plans to invest in an
automated plant in Towanda, Pa., to make PM metallic plates used in fuel cells to meet growing demand for these products. The ultra-thin PM plates are made from a custom metal alloy designed by Plansee engineers to allow fuel-cell stacks to operate at high temperatures without cracking. Carbide Firm Expands Yillik Precision Carbides, division of PSM Industries, Inc., has moved to a new 13,000 sq. ft. building near its former location in Ontario, Calif. The larger plant supports the company’s recent growth into new minia-
ture carbide products for oilfield-equipment, medical, and sporting-goods industries. Canadian Government Loans Funds for Tungsten Project The Ministry of Economic Development and Trade, Ontario, Canada, is providing a Can$4.14 million loan to H.C. Starck Canada to modernize the company’s tungsten powder plant in Sarnia, Ontario. The loan is funded by the province’s Advanced Manufacturing Investment Strategy repayable loan program, which encourages companies to invest in leadingedge technologies and processes. ijpm
Competence Versatility Innovative
MIM Debind and Sinter Furnaces
for Metal and Ceramic Injection Molded Materials t Metal or graphite hot zones t Sizes from 0.3–12 cu ft. t Pressures from 10-6 torr– 750 torr t Operates in Vac, Ar, N2, and H2 t All binders and feedstocks
Over 6000 units built since 1954 Over 80 different styles of batch and continuous furnaces from 1 cu cm to 28 cu m. Custom sizes available. t Testing available in our Applied Technology Center furnaces to 2800°C t Worldwide Field Service and Spare Parts available for all furnace makes and models. t
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MEETINGS AND CONFERENCES
2010 SMST 2010 THE INTERNATIONAL CONFERENCE ON SHAPE MEMORY AND SUPERELASTIC TECHNOLOGIES May 16–20 Pacific Grove, CA www.asminternational.org INTERNATIONAL SYMPOSIUM ON SURFACE HARDENING OF CORROSION RESISTANT ALLOYS May 25–26 Cleveland, OH www.asminternational.org NANOMATERIALS June 8–10 Bad Gastein, Austria www.nanoconsulting.de AEROMAT 2010 June 20–24 Bellevue, WA www.asminternational.org PowderMet2010: MPIF/APMI INTERNATIONAL CONFERENCE ON POWDER METALLURGY & PARTICULATE MATERIALS June 27–30 Hollywood (Ft. Lauderdale), FL MPIF* BASIC PM SHORT COURSE July 25–28 State College, PA MPIF* 1ST TMS-ABM INTERNATIONAL MATERIALS CONFERENCE July 26–30 Rio de Janeiro, Brazil www.tms.org MICROSCOPY & MICROANALYSIS 2010 August 1–5 Portland, OR www.microscopy.org
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
THE 6TH CHINA (BEIJING) INTERNATIONAL GEAR TRANSMISSION AND EQUIPMENT EXPO 2010 August 5–7 Beijing, China www.bjksexpo.com.cn PRICM 7 7TH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING August 1–5 Cairns, Australia www.materialsaustralia.com.a u/scripts/cgiip.exe/WServic e=MA/ccms.r?PageID=19070 ILASS 2010 23rd Annual Conference on Liquid Atomization and Spray Systems September 6–8 Brno, Czech Republic www.ilasseurope2010.org TSS COLD SPRAY CONFERENCE September 27–28 Akron, OH www.asminternational.org PM SINTERING SEMINAR September TBA MPIF* Titanium 2010 October 3–5 Orlando, FL www.titanium.org PM2010 WORLD CONGRESS October 10–14 Florence, Italy www.epma.com/pm2010
7TH INTERNATIONAL SYMPOSIUM ON SUPERALLOY 718 & DERIVATIVES October 10–13 Pittsburgh, PA www.tms.org FORGING, SHEET METAL FORMING & POWDER METALLURGY – LINKING INDUSTRY & TECHNOLOGY October 20–22 Porto Alegre, Brazil www.senafor.com.br
2011 (NOTE: NEW DATES & LOCATION) PowderMet2011: MPIF/APMI INTERNATIONAL CONFERENCE ON POWDER METALLURGY & PARTICULATE MATERIALS May 18–21 San Francisco, CA MPIF* INTERNATIONAL CONFERENCE ON SINTERING 2011 August 28–September 1 Jeju Island, Korea www.sintering2011.org
2012 PowderMet2012: MPIF/APMI INTERNATIONAL CONFERENCE ON POWDER METALLURGY & PARTICULATE MATERIALS June 10–13 Nashville, TN MPIF* SUPERALLOYS 2012: TWELFTH INTERNATIONAL SYMPOSIUM ON SUPERALLOYS September 9–13 Champion, PA
*Metal Powder Industries Federation 105 College Road East, Princeton, New Jersey 08540-6692 USA (609) 452-7700 Fax (609) 987-8523 Visit www.mpif.org for updates and registration. Dates and locations may change
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INSTRUCTIONS FOR AUTHORS International Journal of Powder Metallurgy Instructions for Authors The Journal reports on scientific and technological developments worldwide in the powder metallurgy and particulate materials industries. Articles cover both the scientific/theoretical and practical aspects of the technology. Subjects addressed include: powder production and characterization; compaction; sintering; consolidation to full density; powder injection molding; consolidation to full density; and hybrid particulate processes such as spray forming and thermal spraying. The Journal also embraces review articles, PM industry news, company profiles, a consultants’ corner, newsmakers, conference reports and book reviews. The Journal’s audience includes: powder metallurgists, engineers, researchers, educators, students, technical managers, and users of powders, PM parts and particulate materials. Manuscript Requirements 1. The primary author should be a member of APMI International. 2. a. All manuscripts must be typewritten, double spaced and on one side of the paper only. Authors should limit manuscripts to 10 printed pages in the Journal. For guidance, this is roughly 30 double-spaced pages—including text, references, figures and tables. b. Authors must submit their manuscript on CD, in Microsoft Word, and include three printed copies of the manuscript. All images should be digital, in jpg or tif format, and at least 300 dpi at 4x6 inches. Please include digital images in separate files, as well as included in the text of the manuscript. c. Micrographs must include a magnification marker in the lower right-hand corner. d. Tables and figures must include complete descriptive captions. e. Equations, tables, references and figures should be numbered separately and consecutively throughout the text. f. Papers must be in English, be original and not be published elsewhere. Translated papers published in other languages will be considered provided the author receives permission and submits a copyright release from the publication involved. Particular attention should be given to grammar/syntax; the Journal is not in a position to assist foreign authors in technical writing. 3. Authors and co-authors must provide complete names, mailing addresses, job titles and affiliations, as they wish them to appear in the Journal. A letter accompanying the manuscript should give the name, complete address, telephone number, fax number and e-mail address of the author to whom correspondence should be sent.
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4.
5.
6. 7.
Each paper must include an abstract of approximately 100 words that summarizes concisely the paper’s objectives, methods, results, observations, mode of analysis and conclusions. Système International (SI) units are mandatory. If industrial practice dictates the use of other systems of units, such units must be included in parentheses. As a guide for authors, frequently used SI units and the corresponding conversion factors are provided overleaf. Weight percent, atomic percent and volume percent should be given as w/o, a/o and v/o, respectively. References must be numbered, placed at the end of the paper, and must adhere to the following format: Journal T. Le, R. Stefaniuk, H. Henein and J-Y. Huôt, “Measurement and Analysis of Melt Flowrate in Gas Atomization”, Int. J. Powder Metall., 1999, vol. 35, no. 1, pp. 51–60. Book R.M. German, Powder Metallurgy Science, Second Edition, 1994, Metal Powder Industries Federation, Princeton, NJ. Article in Book/Conference Proceedings S.H. Luk, F.Y. Chau and V. Kuzmicz, “Higher Green Strength and Improved Density by Conventional Compaction”, Advances in Powder Metallurgy & Particulate Materials, compiled by J.J. Oakes and J.H. Reinshagen, Metal Powder Industries Federation, Princeton, NJ, 1998, vol. 3, part 11, pp. 81–99. Patent I.L. Kamel, A. Lawley and M-H. Kim, “Method of Molding Metal Particles”, U.S. Patent No. 5,328,657, July 12, 1994. Thesis D.J. Schaeffler, “High-Strength Low-Carbon Powder Metallurgy Steels: Alloy Development with Transition Metal Additions”, 1991, Ph.D. Thesis, Drexel University, Philadelphia, PA. Technical Report T.M. Cimino, A.H. Graham and T.F. Murphy, “The Effect of Microstructure and Pore Morphology on Mechanical and Dynamic Properties of Ferrous P/M Materials”, 1998, Hoeganaes Technical Data, Hoeganaes Corporation, Cinnaminson, NJ. Web Site Content J.R. Dale, “Connecting Rod Evaluation”, Metal Powder Industries Federation, http://www.mpif. org/design/conrod.pdf Private Communication P.W. Taubenblat, 1999, Promet Associates, Highland Park, NJ, private communication. Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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INSTRUCTIONS FOR AUTHORS
The author(s) will be sent a copyright form, which must be returned before the paper can be published. A reprint order form will also be sent to the author(s). All manuscripts submitted to the Journal should be sent to the Editor-in-Chief, who will make an initial decision on the paper’s suitability for external review. Papers are then subject to review by two members of the Editorial Review Committee. Papers are accepted with the understanding that they may be returned to the author(s) for revision, based on the reviewer’s
recommendations. They may also be edited by the Journal’s staff for clarity and conciseness. Articles should be submitted to: Dr. Alan Lawley Editor-in-Chief International Journal of Powder Metallurgy 105 College Road East Princeton, NJ 08540-6692 USA Questions may be e-mailed to:
[email protected]
SYSTÈME INTERNATIONAL UNITS (SI) AND CONVERSION FACTORS Adapted from: R.M. German, Powder Metallurgy Science, Second Edition, Metal Powder Industries Federation, Princeton, NJ 1994
Length Conversions: 1 m = 39.4 in. (inch) 1 m = 3.28 ft. (foot) 1 m = 1.09 yd. (yard) 1 cm = 0.394 in. (inch) 1 mm = 0.0394 in. (inch) 1 µm = 39.4 µin (microinch) 1 nm = 10 Å (angstrom) Area and Volume Conversions: 1 cm2 = 0.155 in.2 (square inch) 1 m2 = 1,550 in.2 (square inch) 1 cm3 = 0.061 in.3 (cubic inch) 1 m3 = 35 ft.3 (cubic foot) 1 L = 1,000 cm3 (cubic centimeter) 1 L = 0.264 gal. (gallons) 1 L = 1.06 qt. (quart) Amount of Substance Conversion: 1 mol = 6.022·1023 molecules Density Conversions: 1 Mg/m3 = 1 g/cm3 1 g/cm3 = 0.0361 lb./in.3 (pound per cubic inch) 1 kg/m3 = 10-3 g/cm3 Temperature Conversion: to convert K to °F (fahrenheit), multiply by 1.8 then subtract 459.4°F to convert °C to °F (fahrenheit), multiply by 1.8 then add 32°F Heating and Cooling Rate Conversions: 1 K/s = 1°C/s = 1.8°F/s 1 K/min = 1.8°F/min Mass Conversions: 1 g = 0.035 oz. (ounce) 1 kg = 2.2 lb. (pound) 1 Mg = 1.1 ton (ton = 2,000 pounds) Force Conversions: 1 N = 105 dyne 1 N = 0.225 lbf (pound force) Pressure, Stress and Strength Conversions: 1 Pa = 0.0075 torr (millimeter of mercury)
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
1 Pa = 10 dyne/cm2 (dyne per centimeter square) 1 kPa = 0.145 psi (pounds per square inch) 1 MPa = 9.87 bar (atmosphere) 1 MPa = 145 psi (pounds per square inch) 1 MPa = 0.145 kpsi (thousand pounds per square inch) 1 Gpa = 145 kpsi (thousand pounds per square inch) Energy Conversions: 1 J = 9.48 ·10-4 btu (British thermal unit) 1 J = 0.737 ft.·lbf (foot pound force) 1 J = 0.239 cal (calorie) 1 J = 107 erg 1 J = 2.8 ·10-7 kw ·h (kilowatt hour) 1 J = 6.24 ·1018 eV (electron volt) 1 J = 4.83 hp · h (horsepower · hour) 1 J = 1 W· s (watt second) 1 J = 1 V· C (volt coulomb) 1 kJ = 0.239 kcal (kilocalorie) Power Conversions: 1 W = 0.737 ft.· lb./s (foot pound per second) 1 W = 1.34 ·10-3 hp (horsepower) Thermal Conversions: 1 J/(kg · K) = 2.39 ·10-4 btu/(lb .·°F) (British thermal unit per pound per degree fahrenheit) 1 J/(kg · K) = 2.39 ·10-4 cal/(g ·°C) (calorie per gram per degree celsius) 1 W/(m · K) = 0.578 btu/(ft.· h · °F) (British thermal unit per foot per hour per degree fahrenheit) 1 W/(m · K) = 2.39 · 10-3 cal/(cm · s · °C) (calorie per centimeter per second per degree celsius) Viscosity Conversions: 1 Pa· s = 1 kg/(m · s) 1 Pa· s = 10 P (poise) 1 Pa· s = 103 cP (centipoise) Stress Intensity Conversion: 1 MPa · m1/2 = 0.91 kpsi · in.1/2 (kilopounds per square inch times square root inch) Magnetic Conversions: 1 T = 104 G (gauss) 1 A/m = 1.257· 10-2 Oe (oersted) 1 Wb = 108 Maxwell
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MEMBERSHIP APPLICATION Please type or print legibly.
I hereby apply for membership in APMI International. Name (First, Middle Initial, Last) Company
ANNUAL DUES: G United States, Canada and Mexico .............$105.00 G Overseas.......................................................$125.00 G Students (Full-Time Only)..................................$25.00 G Overseas Students (Full-Time Only) ..................$40.00 Payments by check or credit card are acceptable, in US Dollars, drawn on a US bank. Make check payable to APMI International. Upon receipt of full payment, membership will be processed.
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PLEASE CHECK APPROPRIATE BOX Level of Education G High School G Associate Degree G Some College G Bachelor’s Degree
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PLEASE CIRCLE APPROPRIATE NUMBERS (ONLY ONE IN EACH CATEGORY) Primary Job Function Company Primary Function 1 Company Management 1 PM Parts Manufacturer 2 Research & Development 2 Metal Powder Supplier 3 Engineering (incl. Design) 3 User of PM Parts or Products 4 Sales/Marketing 4 Equipment Mfg/Supplier (i.e., presses, furnaces, lab equip., 5 Metallurgical/Laboratory belts, atmospheres, services, etc.) 6 Production/Mfg/Maintenance 5 Consulting or Research 7 Technician 6 Educational Institution 8 Educator 7 MIM—Parts and Suppliers 9 Student 8 HIP/Advanced Particulate Products 10 Human Resources 9 Hardmetals 11 Accounting/IT 10 Other ______________________________ 12 Quality Assurance 13 Other ______________________________ APMI International 105 College Road East, Princeton, New Jersey 08540-6692 USA Phone: 609-452-7700 Fax: 609-987-8523
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PM BOOKSHELF
Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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ADVERTISERS’ INDEX ADVERTISER
FAX
WEB SITE
PAGE
ABTEX CORPORATION _________________(315) 536-0280 ________www.abtex.com _______________________________25 AC COMPACTING_____________________(732) 249-6909 ________www.accompacting.com ________________________41 ACE IRON & METAL CO. INC. ___________(269) 342-0185 ______________________________________________________7 ACUPOWDER INTERNATIONAL, LLC______(908) 851-4597 ________www.acupowder.com ___________________________18 ADVANCED METALWORKING____________(317) 843-9359 ________www.advancedmetalworking.com _________________59 AMETEK SPECIALTY METAL PRODUCTS___(724) 225-6622 ________www.ametekmetals.com _________________________4 ASBURY CARBONS ___________________(908) 537-2908 ________www.asbury.com ______________________________29 BRONSON & BRATTON ________________(630) 570-4866
[email protected] _____________________57 CENTORR VACUUM INDUSTRIES ________(603) 595-9220 ________www.centorr.com ______________________________74 DAEWHA PRESS CO. LTD. _____________+82-31-989-1396_______www.daewha.co.kr_____________________________35 DIEFFENBACHER __________________________________________www.dieffenbacher.com_________________________31 ELNIK SYSTEMS _____________________(973) 239-6066 ________www.elnik.com_________________________________8 GLOBAL TITANIUM ___________________(313) 366-5305 ________www.globaltitanium.com ________________________58 HOEGANAES CORPORATION ____________(856) 786-2574 ________www.hoeganaes.com___________INSIDE FRONT COVER INTERNATIONAL TITANIUM POWDER_______________________________________________________________________26 KITTYHAWK PRODUCTS _______________(714) 895-5024 ________www.kittyhawkinc.com__________________________21 LAUFFER PRESSEN ___________________+49 (0) 74 51/902-100 __www.lauffer.de ________________________________10 LONZA _____________________________(201) 785-9973 ________www.lonza.com _______________________________36 MAGNEQUENCH______________________(65) 6415 0670 ________www.mqitechnology.com ________________________45 MOLDED FIBER GLASS TRAY COMPANY __(814) 683-4504 ________www.mfgtray.com______________________________33 NORTH AMERICAN HÖGANÄS INC._______(814) 479-2003 ________www.nah.com__________________________________3 OSTERWALDER ______________________(513) 936-9006 ________www.osterwalder.com __________________________15 RIO TINTO METAL POWDERS/ QUEBEC METAL POWDERS LIMITED ____(734) 953-0082 ________www.qmp-powders.com ________________BACK COVER SCM METAL PRODUCTS, INC. __________(919) 544-7996 ________www.scmmetals.com ____________INSIDE BACK COVER SURFACE COMBUSTION _______________(419) 891-7151 ________www.surfacecombustion.com ____________________16 TEKNA PLASMA SYSTEMS INC. _________(819) 820-1502 ________www.tekna.com _______________________________22 TIMCAL ____________________________+41-91-873-2009_______www.timcal.com_______________________________39 UNION PROCESS _____________________(330) 929-3034 ________www.unionprocess.com _________________________13
ADVERTISER’S REQUEST FOR INFORMATION FAX FORM Need more information on products or services seen in this issue?
Complete the form below and fax to the advertiser(s) of your choice. Fax numbers are listed in the advertisers’ index above.
To:___________________________________ Fax #: ______________________________________ Company: _________________________________________________________________________ Please send me more information on:_____________________________________________________ _________________________________________________________________________________ as advertised in the __________ issue of the International Journal of Powder Metallurgy. Please send information to: Name: Title: ________________________________________________________________________ Company: _________________________________________________________________________ Address:___________________________________________________________________________ City:____________________________ State:_______________ Postal Code: ___________________ Country:___________________________________________________________________________ Phone:___________________ Fax:___________________ E-Mail: ___________________________
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Volume 46, Issue 3, 2010 International Journal of Powder Metallurgy
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A COMMITTED BUSINESS & TECHNICAL PARTNER
Metal Powders
www.qmp-powders.com
