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Application of metal injection moulding (MIM) to Ti alloys
PM
PRODUCTS: Metal injection moulding
LITERATURE
REVIEW
O P T I M I Z A T I O N OF METAL INJECTION MOULDING (MIM): EXPERIMENTAL DESIGN
I lrl
DISTORTION DURING WICK DEBINDING OF INJECTION MOULDED COMPACTS R.M. German, et al, (Rensselaer Polytechnic Institute, Troy, New York, USA), Int J. Powder Metallurgy., Vol 26, No 3, 1990, 217-230. The paper draws a t t e n t i o n to the importance of dimensional control in the production of PM parts. An analytical and e x p e r i m e n t a l s t u d y of d i m e n s i o n a l distortion during debinding of metal injection moulded (MIM) parts, with a multicomponent binder, is described. The following observations are reported. During heating, gravitational stresses cause viscous flow which continues until the binder content has dropped to a critical level which d e p e n d s on powder size a n d particle shape. Minimization of distortion requires a maximum initial solid fraction and controlled heating rates. Good shape preservation is reported on heating at I°C/ min below l l0°C. A conceptual model is used to illustrate the use of non-isothermal heating to minimize distortion. INJECTION MOULDING OF CERAMICS MJ. Edirisinghe (Brunel University, Uxbridge, UK), Metals and Materials, Vol 6, No 6, 1990, 367-370 The application of injection moulding to ceramics is described. The four stages, blending, moulding, binder removal and sintering are discussed. Processing defects are tabulated. PROPERTIES AND STRUCTURE OF Ag-Sn COMPACTS DURING LIQUID PHASE SINTERING T. Piszcek, S. Stolarz (Inst. Metali Niezel, Griwice, Poland), Metalu~gia Proszkow, Vol 23, No 1, 1990, 3-7. In Polish The compacts were sintered at various temperatures and various times. First stages of sintering below tin melting point, may be analysed based on the mechanism of sintering in solid state. In the second stage, the capillary flow takes place followed by AgaSn phase formation. That phenomena is accompanied by a strong increase of the electrical resistivity value and decrease of the sintered material density. Sintering in thetemperature above 490°C results in the AgaSn phase formation accompanied by a strong densification of material, decrease of electrical resistivity and increase of density.
54 MPR February 1991
R.T. Fox, D. Lee, (Rensselaer Polytechnic Institute, Troy, New York, USA), Int J. Powder Metallurgy., Vol 26, No 3, 1990, 233-243 MIM of metal powder mixed with a plastic binder was optimized. The process parameters investigated were barrel and die temperatures, injection speeds and profiles, packing pressures and profiles, and packing and cooling times. The methods of Taguchi were used to improve control of green part dimensions and integrity. Additionally, the optimization procedures predicted the conditions under which void formation d u r i n g injection, as detected by Xradiography, was avoided. Specimens were debound and sintered and mechanical properties measured. The defect free specimens were found to have improved properties. REVIEW OF METAL INJECTION MOULDED (MIM) MATERIALS STANDARDS P. Bhave, (MIMA Standards Committee, Wilsonville, Oregon, USA), Int J. Powder Metallurgy, Vol 26, No 3, 1990, 277-280 The paper draws attention to the need for revised testing procedures for materials. It is recommended that (a) a new standard is drawn up, (b) that the results of testing are published and (c) that a programme of impact and fatigue testing is undertaken. SINTERING BEHAVIOUR AND MAGNETIC PROPERTIF_~ OF METAL INJECTION MOULDED (MIM) Fe-Co ALLOYS Y. Kiyota, H. Ohtsubo, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No 5, 1990, 601-604, In Japanese Specimens of Fe-5%Co were prepared by MIM from carbonyl Fe and reduced Co powders and the sintering behaviour investigated. It was found that sintering in the a region was effective in densifying the alloys but in the 7-phase region pore s p h e r o i d i z a t i o n and grain growth occurred. Two stage sintering first in the and then in the 7 phase region enabled high flux density to be attained and also high permeability.
APPLICATION OF METAL INJECTION MOULDING (MIM) TO Ti ALLOYS Y. Kaneko, et al, J. Japan Soc., Powder and Powder Metallurgy, Vol 37, No 5, 1990, 605607. In Japanese
Samples of Ti-5%Co and Ti-6%Al-4%Vwere produced by MIM. A wax-acrylate-atactic polypropylene mixture was used as the binder, C and O contents were lower when a two stage de-binding process was used. Two phase structures were observed in the alloys. Sintering at 1300°C, in vacuum, gave 95% relative density. EFFECT OF DEBINDING CONDITIONS ON SINTERING OF INJECTION MOULDED STAINLESS STEEL POWDERS J. Tatekawa, J. Japan Soc., Powder and Powder Metallurgy, Vol 37, No 5, 1990, 608611. In Japanese The d e b i n d i n g p r o c e s s a n d t h e relationships between % residual binder and the sintering characteristics of 316L stainless steel were investigated. It was found that (a) % binder removal is proportional to the specific surface, (b) the relative density of the sintered compact increases with increased binder removal and (c) low binder removal resulted in grain growth and grain b o u n d a r y precipitation of carbides.
Refractory metals Ir
I
I
EFFECT OF HEAT TREATMENT OF STRUCTURE AND PROPERTIES OF W ALLOYS I~ B. Pavarova, E.I~ Zararzina, Russian Metallurgy, 1989, No 5, 112-119. Structure and properties of W alloyed with Y and Hf oxide (for dispersion strengthening), Mo and Re (for solid solution strengthening) and Hf and Zr carbides (for precipitation hardening) were investigated. Strengthening mechanisms analysed and property values reported.
BUBBLE FORMATION IN HIPED, DOPED Mo WIRE J. Choi, et al, (Korea Inst. of Science and Technology, Seoul, Korea), Metallurgical Truns A, Vol 21A, No 4, 1990, 919-923 Materials entrapped in bubbles formed in K and Si doped Mo wire were analysed by SEM with energy dispersive spectroscopy. These were found to be leucite type (A1-SiK). On heating to 1900°C particles showed partial volatilization leaving a mullite type of residue. Deduced that the formation of b u b b l e s i n Mo w i r e d u e to t h i s volatilization. EFFECT OF TEMPERATURE ON HARDNESS OF Mo-Ni ALLOYS V~A. Goncharuk, et al, Poroskovaya Metallurgia, 1989, No 10, 93-97. (In Russian)
PRODUCTS: Metal injection moulding
LITERATURE
REVIEW
O P T I M I Z A T I O N OF METAL INJECTION MOULDING (MIM): EXPERIMENTAL DESIGN
I lrl
DISTORTION DURING WICK DEBINDING OF INJECTION MOULDED COMPACTS R.M. German, et al, (Rensselaer Polytechnic Institute, Troy, New York, USA), Int J. Powder Metallurgy., Vol 26, No 3, 1990, 217-230. The paper draws a t t e n t i o n to the importance of dimensional control in the production of PM parts. An analytical and e x p e r i m e n t a l s t u d y of d i m e n s i o n a l distortion during debinding of metal injection moulded (MIM) parts, with a multicomponent binder, is described. The following observations are reported. During heating, gravitational stresses cause viscous flow which continues until the binder content has dropped to a critical level which d e p e n d s on powder size a n d particle shape. Minimization of distortion requires a maximum initial solid fraction and controlled heating rates. Good shape preservation is reported on heating at I°C/ min below l l0°C. A conceptual model is used to illustrate the use of non-isothermal heating to minimize distortion. INJECTION MOULDING OF CERAMICS MJ. Edirisinghe (Brunel University, Uxbridge, UK), Metals and Materials, Vol 6, No 6, 1990, 367-370 The application of injection moulding to ceramics is described. The four stages, blending, moulding, binder removal and sintering are discussed. Processing defects are tabulated. PROPERTIES AND STRUCTURE OF Ag-Sn COMPACTS DURING LIQUID PHASE SINTERING T. Piszcek, S. Stolarz (Inst. Metali Niezel, Griwice, Poland), Metalu~gia Proszkow, Vol 23, No 1, 1990, 3-7. In Polish The compacts were sintered at various temperatures and various times. First stages of sintering below tin melting point, may be analysed based on the mechanism of sintering in solid state. In the second stage, the capillary flow takes place followed by AgaSn phase formation. That phenomena is accompanied by a strong increase of the electrical resistivity value and decrease of the sintered material density. Sintering in thetemperature above 490°C results in the AgaSn phase formation accompanied by a strong densification of material, decrease of electrical resistivity and increase of density.
54 MPR February 1991
R.T. Fox, D. Lee, (Rensselaer Polytechnic Institute, Troy, New York, USA), Int J. Powder Metallurgy., Vol 26, No 3, 1990, 233-243 MIM of metal powder mixed with a plastic binder was optimized. The process parameters investigated were barrel and die temperatures, injection speeds and profiles, packing pressures and profiles, and packing and cooling times. The methods of Taguchi were used to improve control of green part dimensions and integrity. Additionally, the optimization procedures predicted the conditions under which void formation d u r i n g injection, as detected by Xradiography, was avoided. Specimens were debound and sintered and mechanical properties measured. The defect free specimens were found to have improved properties. REVIEW OF METAL INJECTION MOULDED (MIM) MATERIALS STANDARDS P. Bhave, (MIMA Standards Committee, Wilsonville, Oregon, USA), Int J. Powder Metallurgy, Vol 26, No 3, 1990, 277-280 The paper draws attention to the need for revised testing procedures for materials. It is recommended that (a) a new standard is drawn up, (b) that the results of testing are published and (c) that a programme of impact and fatigue testing is undertaken. SINTERING BEHAVIOUR AND MAGNETIC PROPERTIF_~ OF METAL INJECTION MOULDED (MIM) Fe-Co ALLOYS Y. Kiyota, H. Ohtsubo, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No 5, 1990, 601-604, In Japanese Specimens of Fe-5%Co were prepared by MIM from carbonyl Fe and reduced Co powders and the sintering behaviour investigated. It was found that sintering in the a region was effective in densifying the alloys but in the 7-phase region pore s p h e r o i d i z a t i o n and grain growth occurred. Two stage sintering first in the and then in the 7 phase region enabled high flux density to be attained and also high permeability.
APPLICATION OF METAL INJECTION MOULDING (MIM) TO Ti ALLOYS Y. Kaneko, et al, J. Japan Soc., Powder and Powder Metallurgy, Vol 37, No 5, 1990, 605607. In Japanese
Samples of Ti-5%Co and Ti-6%Al-4%Vwere produced by MIM. A wax-acrylate-atactic polypropylene mixture was used as the binder, C and O contents were lower when a two stage de-binding process was used. Two phase structures were observed in the alloys. Sintering at 1300°C, in vacuum, gave 95% relative density. EFFECT OF DEBINDING CONDITIONS ON SINTERING OF INJECTION MOULDED STAINLESS STEEL POWDERS J. Tatekawa, J. Japan Soc., Powder and Powder Metallurgy, Vol 37, No 5, 1990, 608611. In Japanese The d e b i n d i n g p r o c e s s a n d t h e relationships between % residual binder and the sintering characteristics of 316L stainless steel were investigated. It was found that (a) % binder removal is proportional to the specific surface, (b) the relative density of the sintered compact increases with increased binder removal and (c) low binder removal resulted in grain growth and grain b o u n d a r y precipitation of carbides.
Refractory metals Ir
I
I
EFFECT OF HEAT TREATMENT OF STRUCTURE AND PROPERTIES OF W ALLOYS I~ B. Pavarova, E.I~ Zararzina, Russian Metallurgy, 1989, No 5, 112-119. Structure and properties of W alloyed with Y and Hf oxide (for dispersion strengthening), Mo and Re (for solid solution strengthening) and Hf and Zr carbides (for precipitation hardening) were investigated. Strengthening mechanisms analysed and property values reported.
BUBBLE FORMATION IN HIPED, DOPED Mo WIRE J. Choi, et al, (Korea Inst. of Science and Technology, Seoul, Korea), Metallurgical Truns A, Vol 21A, No 4, 1990, 919-923 Materials entrapped in bubbles formed in K and Si doped Mo wire were analysed by SEM with energy dispersive spectroscopy. These were found to be leucite type (A1-SiK). On heating to 1900°C particles showed partial volatilization leaving a mullite type of residue. Deduced that the formation of b u b b l e s i n Mo w i r e d u e to t h i s volatilization. EFFECT OF TEMPERATURE ON HARDNESS OF Mo-Ni ALLOYS V~A. Goncharuk, et al, Poroskovaya Metallurgia, 1989, No 10, 93-97. (In Russian)