Transverse rupture, yield stress, strain at fracture, ductile-brittle transitions and strain hardening parameters were determined. It is shown that very high strain hardening occurs in WC-Co alloys. The dominant mechanism at 1000°C, for submicron grades and deformation rates of 7xl0-Ssec-1 was shown to be grain boundary sliding, which is typical of superplastic deformation.
Effects of grain size on corrosion resistance of tungsten carbide-cobalt Y.Hayashi et al. (Kyushu University, Fukuoka, Japan.) J.Japan Soc Powder/Powder Metall., Vo148, No 7, 2ool, 6o9-615. In Japanese. Properties of WC-Co were discussed with reference to effects of WC grain size. Investigation of corrosion resistance of WC-15%Co, with regard to effects of WC grain size, is described. Immersion and polarisation tests were used. Aqueous 3%NaCI-0.1N H2SO4 leached more Co than 3%NaCI. Dissolution of metal decreased with decrease in WC grain size and C content. In polarisation tests both W and Co were dissolved. It is deduced that reduction in WVC grain size increased corrosion resistance.
Cemented carbide with an iron aluminide binder K.Ozaki et al. (National Inst. for Advanced Industrial Science and Technology, Nagoya, Japan.) J.Japan Soc Powder/Powder Metall., Vol 48, No 7, 2001, 616-620 .In Japanese. Structure
properties of WClOwt%(Fe-25at%Al), WC-10wt%(F e22.Sat%AI-5%B) and WC-20wt%(Fe25at%A1) were investigated. Sample preparation is described. Use was made of mechanical alloying and wet or dry mixing. Density and hardness of WC-10%(FeA1-B) were higher than WC-10%(Fe-AI) but both had low transverse rupture strength due to high O content. Rockwell hardness of WC-10% (Fe-AI) was 93A and of WC-20% (Fe-AI) 90.5A.
Structural evolution and properties of novel tungsten carbide-cobalt hardmetal K.Hayashi et at. (University of Tokyo, Tokyo, Japan.) J.Japan Soc Powder/Powder Metall., Vo148, No 7, 20ol,621-628 .In English
It is noted that WC-Co, made from WCo-C powders rather than WC and Co, had triangular prismatic WC grains, higher transverse rupture strength and fracture toughness than conventional WC-Co. Production of WC-Co from a complex WCoC precursor and graphite was described, k, W9Co3C 4 and q, W4Co2C phases were used with additional graphite. Structures were similar to samples made from W-Co-C powders. Fracture toughness was higher and transverse rupture strength was similar to conventional WC-Co materials.
Synthesis of monocarbonitrdes of tungsten molybdenum and tungsten-molybdenum heated in methane-nitrogen K.Tanaka, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J.Japan Soc Powder/Powder Metall., Vo148, No 7, 2ool,629-635. In English. It is reported that W(C,N), Mo(C,N) and (W,Mo)(C,N) had been synthesised by heating W, Mo and W-Mo powders at 1100°C to 1300°C in CH4-N2. It is shown that carbides or nitrides are formed before synthesis of the carbonitrides. Possible mechanisms are suggested.
Effects of boron content on properties of boron carbide-(tungsten, molybdenum) boride hardmetal M.Yokouchi. (Kanagawa Industrial Technology Research Inst, Ebina, Japan.) J.Japan Soc Powder/Powder Metal[., Vo[ 48, No 7, 2ool,66o-664 .In Japanese. It is noted that needle-like crystals of (W,Mo)B 2 had been found in samples of B4C-(W, Mo)B 2. These are shown to increase bend strength and fracture toughness. It was found that C deposited during processing reduced strength and additional B powder was added to counteract this. Effects of %B on properties were investigated. Addition of B powder inhibited deposition of C, increased Vickers's hardness but reduced bend strength and fracture toughness.
IntermetalUc materials High-temperature mechanical properties of two-phase nickel aluminides reinforced with titanium carbide particles K.Matsuki et al. (Toyama University, Toyama, Japan.) j.Japan Soc Powder/Powder Metall.,
V 0[ 48, No 7, 20ol,648-654. In Japanese. Two-phase Ni aluminides, gNi3Al-b NiA1, with and without TiC particle reinforcements, were prepared by wet mechanical alloying and vacuum hot pressing. Effects of two types of heat treatment on structure and properties were investigated. The change sought was from fine to coarse structure for strengthening after superplastic deformation, which requires a fine structure. The heat treatment was 1350°C for 12hours and increased grain size from 1.2mm to 14mm, without TiC and 0.9mm to 8mm with TiC. A lamellar structure was attained by oil quenching from 1350°C and tempering at 700°C or ll00°C. Effects of the heat treatments on properties are described.
Metal !njection moulding Metal injection moulding in Japan Y.M.Li et al. (Central South University of Technology, Changsha, China.) PM Industry, Vo111, No 4, 2ool, 33"37. In Chinese. The current status of MIM in Japan is reviewed. Processes, products and economics are discussed with regard to a number of commercial companies.
PM components Porous sintered bearings T,Watanabe. (Waseda University Tokyo, Japan.) J.Japan Soc Powder/Powder Metall., Vo[ 48, No 9, 2ooi, 769-776. In Japanese. Porous sintered bearings are discussed with regard to porosity and the incorporation of lubricant in pores. An outline of sintered bearing materials is presented. The author's researches are reviewed and future trends are indicated.
Production of PM gears by cold extrusion H.H.Wang. (Qingdao PM Plant, Shandong, Qingdao, China.) PM Industry, Vo111, No 4, 2001, 22-24. In Chinese. Experimental production of PM gears by cold extrusion is described. Equipment, tooling and parts precision are considered. Causes of component failure are indicated.