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Nanopowders for PIM

Nanopowders for PIM. KE-31.5530 Nanoparticles Arno Lehtonen 4. 5. 2011. Why Injection Moulding ?.

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Nanopowders for PIM

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  1. Nanopowders for PIM KE-31.5530 Nanoparticles Arno Lehtonen 4. 5. 2011

  2. WhyInjectionMoulding? For complex shaped components powder injection moulding (PIM) is the technology of choice since it is capable of producing near-net-shape parts in highly automated serial production. Four manufacturing steps have to be carried out: compounding of feedstock, injection moulding, debinding and sintering.

  3. PowderInjectionMouldingProcess

  4. Why PIM and Nanopowders? • PIM = P (powder properties) + IM (forming) • Rheology; thindetails (MST-parts) • The general rule is that the minimum feature that can be produced is ten times the particle size • Mechanicalproperties (Drills, cuttingtools) • Availablepowders: Copper, iron, tungsten, cobalt, zirconia, alumina, tungsten carbide

  5. General Powder Requirements • Grain size and size distribution • Grain form • No agglomerates • No surface contamination • No closed pores

  6. Formulating and Mixing Feedstock • Most binder systems consist of waxes and polymers • Surface active component • Requirements: Excellent flowability, high solids loading, form retaining ability and easy debinding

  7. Powder Loading

  8. Binder System for Cemented Carbides • Melting range C Evaporation C • 49 % Parafiin 43 - 66 230  • 39 % Polypropylen 170 350  • 10 % Carnauba-vax 83 - 86 280  • 2 % Stearinic accid 70 190 

  9. Vacuum Z-blade mixer

  10. Injection Moulding • Homogenous filling of the mould cavity • Low internal stress • Elimination of weld lines

  11. Flow Patterns and Weld Lines

  12. JSW 50 ton injection moulding unit

  13. Debinding • Vacuum assisted thermal treatment • As wax komponents evaporate, they create chanels for escaping gasses • Rearrangement of particles • Forming of form sustaining sceleton

  14. Debinding Defects

  15. Sintering • Vacuum and / or pressure assisted thermal treatment • High density part; shrinkage • Porosity, chemical balance • Grain growth; inhibitors

  16. Phase diagram of the W–C system

  17. Problemswith IM Nanopowders • Pyrophoricity, working hazards • Large specific surface area and the associated tendency to agglomerate • Effects of storage time to feedstock • Defects can be created in the bebinding stage; capillary forces • Grain growthduring sintering

  18. Grain Growth

  19. References(1/3) • Influence of dispersant, storage time and temperature on the rheological properties of zirconia–paraffin feedstocks for LPIM • Fatih A. Cetinel , Werner Bauer, Marcus Müller, Regina Knitter, Jürgen Haußelt • Journal of the European Ceramic Society 30 (2010) 1391–1400 • Micro powder injection moulding • Rudolf Zauner • Microelectronic Engineering 83 (2006) 1442–1444 • "The smaller they come, the harder they get"; metal-powder.net, December 2005 • Micro powder injection moulding of alumina micro-channel part • Junhu Menga, Ngiap Hiang Loha, Gang Fua, Bee Yen Tay, Shu Beng Tor • Journal of the European Ceramic Society 31 (2011), 1049 – 1056 • RM. Materials for microminiature powder injection molded medical and dental devices • German • Int. J. Powder Metall 2010;46:15–8.

  20. References(2/3) • Powder-binder separation in injection moulded green parts • Anne Mannschatz, Sören Höhn, Tassilo Moritz • Journal of the European Ceramic Society 30 (2010), 2827 – 2832 • Simulation of Micro Powder Injection Moulding: Powder Segregation and Yield Stress Effects during Form Filling • Andreas Greiner et al. • Journal of the European Ceramic Society (2011) • Debinding behaviors of injection molded ceramic bodies with nano-sized pore channels during extraction using supercritical carbon dioxide and n-heptane solvent • Sang Woo Kim • J. of Supercritical Fluids 51 (2010) 339–344 • An experimental study of the sintering of nanocrystalline WC–Co powders • Z. Fang, P. Maheshwari, X. Wang, H.Y. Sohn, A. Griffo, R. Riley • International Journal of Refractory Metals & Hard Materials 23 (2005) 249–257 • Grain growth during the early stage of sintering of nanosized WC–Co powder • Xu Wang, Zhigang Zak Fang , Hong Yong Sohn • International Journal of Refractory Metals & Hard Materials 26 (2008) 232–241

  21. References (3/3) • Sintering of nano-sized WC–Co powders produced by a gas reduction–carburization process • Gwan-Hyoung Lee, Shinhoo Kang • Journal of Alloys and Compounds 419 (2006) 281–289 • Other reading: • Powder Injection Molding • Randall M. German • MPIF, Princeton, New Jersey; 1990, ISBN 0-918404-95-9 • Keraamien ruiskupuristus • Minna-Liisa Vesanen • DI-työ, TTKK:n Konetekniikan osasto, 1988

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