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

2. 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. Why Injection Moulding?

3. Powder Injection Moulding Process

4. Why PIM and Nanopowders? PIM = P (powder properties) + IM (forming) Rheology; thin details (MST-parts) The general rule is that the minimum feature that can be produced is ten times the particle size Mechanical properties (Drills, cutting tools) Available powders: 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  CEvaporation  C 49 % Parafiin43 - 66230  39 % Polypropylen170350  10 % Carnauba-vax83 - 86280  2 % Stearinic accid70190 

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. Problems with 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 growth during 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