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Synthesis of vanadium and chromium carbide grain growth inhibitors
to be free of internal defects. In Mo-Si only MoSi, was detected. In Mo-Si-Nb, Ni,Si,, MosSi, and unreacted Nb were found in addition. Nb addition resulted in reduction in Young’s modulus and bend strength. DEFORMATION OF TITANIUM ALUMINIDE CONTAINING TITANIUM NITRIDE PARTICLES
SOchiai et al. (Teikyo University of Science and Technology, Yamanashi, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 6, 1997, 577-581. (In Japanese.) TiAl-AlN composites were prepared by mechanical alloying and HIP from Ti, Al and TIN powders. Microstructure and elevated temperature mechanical properties were determined. There was some amorphization during MA. As the %TiN was increased the structure was refined. Ti,AlN and T&Al were detected as well as TiAl. Flow stress was increased by increased %TiN and strength did not decline with increased temperature. Superplasticity was found in the material.
Powder injection moultfing CONSIDERATION OF FINE POWDERS FOR INJECTION MOULDING OF CERAMICS AND HARDMETALS
L.Nyborg et al. (Chalmers University of Technology, Goteborg, Sweden.) Powder Metall., Vo141, No 1, 1998,41-45. It is noted that particle agglomeration occurs to an increasing extent, in ceramic and hardmetal powders, as particle size is reduced and that this increases injection moulding feedstock viscosity. Additives can be used to minimize agglomeration and a model for this is presented. The object is to reduce van der Waals forces by a thin adsorbed film on the particles without increasing particle size, thereby reducing viscosity. Additives are shown to be short molecules such as stearic acid. INJECTION MOULDING OF ELECTROLYTIC COPPER POWDER
N.Wada et al. (Ritsumeikan University, Kusatsu, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 6, 1997, 596603. (In English.) A comparative study of parts made from water atomized Cu-Ni alloy powder and from elemental electrolytic Cuwater atomized Ni powders is described. Cu content of each was 69.4%, the feedstock 56% solids and the binder was a polybutylmethacrylate-ethylene vinyl acetate copolymer-paraffin wax mix-
ture. Samples made from the prealloyed powder sintered to the lower density in N but had higher density on vacuum sintering.
ores and processing, scrap and stockpiling were discussed. Demand and prices for W and Co were considered in the light of traditional and novel applications.
COMPARISON OF INJECTION MOULDED PARTS MADE FROM PREALLOYED AND ELEMENTAL POWDERS
PRODUCTION AND PROPERTIES HIGH QUALITY SUBMICRON
N.Wada et al. (Ritsumeikan University, Kusatsu, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 6, 1997, 604611. (In English.) Production of parts sintered from electrolytic Cu powders is discussed. A study of the effect of particle size, 11.27, 18.89 and 26.83 pm respectively, is described. The 18.89 pm powder is shown to be the most suitable for MIM. For attainment of high density the requirements of the Cu powder are low 0 and C contents and treatment in H at 700°C for 2 hours. A density of 95.6% was attained using a feedstock with a 57.5% solids content. PM
components
DEVELOPMENT OF PM GEAR TOOTH AND BEARING SURFACES FOR HIGH STRESS APPLICATIONS
K.Buckley-Golder et al. (Stackpole Ltd, Mississuaga, Canada.) Znt. J. Powder Metal, Vol 34, No 1, 1998,26-33. It is noted that long term growth in the use of PM parts in automotive powertrain applications will depend on raising all the characteristics of PM steels to those of heat treated low alloy conventional steels. Factors which determine durability of PM parts are reviewed with particular reference to surface endurance. Test data is presented for alloys sintered at high temperatures selectively densified to full density Test methods are discussed in the context of production of high performance gear parts.
TUNGSTEN
CARBIDE
The following Abstracts are
of papers that were presented at the 1998 International Conference on Powder Metallurgy and Particulate Materials held in Las Vegas, NV, USA, in June 1998.
Cemented
carbides
COBALT AND TUNGSTEN AND DEMAND
SUPPLY
K.B.Shedd. (US Geological Survey, USA.) Supply of W and Co were reviewed with regard to differences and similarities between the two commodities. Mining of
POWDERS
C.L.Connor. (Dow Chemical Co, USA.) Manufacture of fine WC powders, in three size grades, superfine, ultrafine and fine, was discussed with reference to applications and capabilities of the three grades. Finer WC and solid solution grades were considered. NEW INTERMEDIATES
FOR HARD
METALS
B.Gries, J.Bredthauer. (H.C.Starck AG, Germany) Trends in hardmetal production, use of fine WC particle sizes and size distribution, morphology of the hard phase and replacement of the Co binder were discussed. It was suggested that characteristics of submicron powders do not allow production of hardmetals in the same way as is the case with micron sized powders. SYNTHESIS
OF VANADIUM
CHROMIUM
CARBIDE
GROWTH
AND
GRAIN
INHIBITORS
B.H.Kear et al. (Rutgers University, New Jersey, USA.) It was reported that a new method had been developed for production of C and Cr carbides. The process involves gas phase carburization of V or Cr metals instead of a solid phase method. The gas phase method works at 900°C lower than is required for the solid phase process. Characteristics of the gas phase carburized V and Cr carbide powders were described. DEVELOPMENTS IN NAN’O- AND MICRO-GRAIN TUNGSTEN CARBIDECOBALT COMPOSITE
PM*TEC’98.
OF
POWDERS
L.Gao, P.Seegopaul. (Nanodyne Inc, USA. 1 The importance of control of particle size and %C in cemented carbides was emphasized. Addition of grain growth inhibitors and mechanical powder mixing were noted. Mechanical mixing may leave powders with segregation of partiand inhomogeneous cles by size inhibitor distribution. It was reported that inhibitors had been deposited from solutions onto the WC and Co particles and this was shown to overcome the latter problem. Processing methods with emphasis on grain growth and C balance were reviewed.
MPR December
1998
39
SOchiai et al. (Teikyo University of Science and Technology, Yamanashi, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 6, 1997, 577-581. (In Japanese.) TiAl-AlN composites were prepared by mechanical alloying and HIP from Ti, Al and TIN powders. Microstructure and elevated temperature mechanical properties were determined. There was some amorphization during MA. As the %TiN was increased the structure was refined. Ti,AlN and T&Al were detected as well as TiAl. Flow stress was increased by increased %TiN and strength did not decline with increased temperature. Superplasticity was found in the material.
Powder injection moultfing CONSIDERATION OF FINE POWDERS FOR INJECTION MOULDING OF CERAMICS AND HARDMETALS
L.Nyborg et al. (Chalmers University of Technology, Goteborg, Sweden.) Powder Metall., Vo141, No 1, 1998,41-45. It is noted that particle agglomeration occurs to an increasing extent, in ceramic and hardmetal powders, as particle size is reduced and that this increases injection moulding feedstock viscosity. Additives can be used to minimize agglomeration and a model for this is presented. The object is to reduce van der Waals forces by a thin adsorbed film on the particles without increasing particle size, thereby reducing viscosity. Additives are shown to be short molecules such as stearic acid. INJECTION MOULDING OF ELECTROLYTIC COPPER POWDER
N.Wada et al. (Ritsumeikan University, Kusatsu, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 6, 1997, 596603. (In English.) A comparative study of parts made from water atomized Cu-Ni alloy powder and from elemental electrolytic Cuwater atomized Ni powders is described. Cu content of each was 69.4%, the feedstock 56% solids and the binder was a polybutylmethacrylate-ethylene vinyl acetate copolymer-paraffin wax mix-
ture. Samples made from the prealloyed powder sintered to the lower density in N but had higher density on vacuum sintering.
ores and processing, scrap and stockpiling were discussed. Demand and prices for W and Co were considered in the light of traditional and novel applications.
COMPARISON OF INJECTION MOULDED PARTS MADE FROM PREALLOYED AND ELEMENTAL POWDERS
PRODUCTION AND PROPERTIES HIGH QUALITY SUBMICRON
N.Wada et al. (Ritsumeikan University, Kusatsu, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 6, 1997, 604611. (In English.) Production of parts sintered from electrolytic Cu powders is discussed. A study of the effect of particle size, 11.27, 18.89 and 26.83 pm respectively, is described. The 18.89 pm powder is shown to be the most suitable for MIM. For attainment of high density the requirements of the Cu powder are low 0 and C contents and treatment in H at 700°C for 2 hours. A density of 95.6% was attained using a feedstock with a 57.5% solids content. PM
components
DEVELOPMENT OF PM GEAR TOOTH AND BEARING SURFACES FOR HIGH STRESS APPLICATIONS
K.Buckley-Golder et al. (Stackpole Ltd, Mississuaga, Canada.) Znt. J. Powder Metal, Vol 34, No 1, 1998,26-33. It is noted that long term growth in the use of PM parts in automotive powertrain applications will depend on raising all the characteristics of PM steels to those of heat treated low alloy conventional steels. Factors which determine durability of PM parts are reviewed with particular reference to surface endurance. Test data is presented for alloys sintered at high temperatures selectively densified to full density Test methods are discussed in the context of production of high performance gear parts.
TUNGSTEN
CARBIDE
The following Abstracts are
of papers that were presented at the 1998 International Conference on Powder Metallurgy and Particulate Materials held in Las Vegas, NV, USA, in June 1998.
Cemented
carbides
COBALT AND TUNGSTEN AND DEMAND
SUPPLY
K.B.Shedd. (US Geological Survey, USA.) Supply of W and Co were reviewed with regard to differences and similarities between the two commodities. Mining of
POWDERS
C.L.Connor. (Dow Chemical Co, USA.) Manufacture of fine WC powders, in three size grades, superfine, ultrafine and fine, was discussed with reference to applications and capabilities of the three grades. Finer WC and solid solution grades were considered. NEW INTERMEDIATES
FOR HARD
METALS
B.Gries, J.Bredthauer. (H.C.Starck AG, Germany) Trends in hardmetal production, use of fine WC particle sizes and size distribution, morphology of the hard phase and replacement of the Co binder were discussed. It was suggested that characteristics of submicron powders do not allow production of hardmetals in the same way as is the case with micron sized powders. SYNTHESIS
OF VANADIUM
CHROMIUM
CARBIDE
GROWTH
AND
GRAIN
INHIBITORS
B.H.Kear et al. (Rutgers University, New Jersey, USA.) It was reported that a new method had been developed for production of C and Cr carbides. The process involves gas phase carburization of V or Cr metals instead of a solid phase method. The gas phase method works at 900°C lower than is required for the solid phase process. Characteristics of the gas phase carburized V and Cr carbide powders were described. DEVELOPMENTS IN NAN’O- AND MICRO-GRAIN TUNGSTEN CARBIDECOBALT COMPOSITE
PM*TEC’98.
OF
POWDERS
L.Gao, P.Seegopaul. (Nanodyne Inc, USA. 1 The importance of control of particle size and %C in cemented carbides was emphasized. Addition of grain growth inhibitors and mechanical powder mixing were noted. Mechanical mixing may leave powders with segregation of partiand inhomogeneous cles by size inhibitor distribution. It was reported that inhibitors had been deposited from solutions onto the WC and Co particles and this was shown to overcome the latter problem. Processing methods with emphasis on grain growth and C balance were reviewed.
MPR December
1998
39