powder produced. Researches aimed at eliminating grinding from the garnet production process, and resultant contamination, are described. IMPROVEMENT IN HIGH TEMPERATURE STRENGTH OF MULLITE BY SILICON CARBIDE PARTICLES
S.Sato et al. (NGK Spring Co Ltd, Yokohama, Japan.) J. Jpn. Sot. Powder Vol 43, No 12, 1996, Powder Metall., 1429-1434. (In Japanese.) Production of a mullite composite containing 20~01% 0.12 to 1.71 pm SIC particles was reported. Compacts were hot pressed at 1650°C and 35 MPa for 4 hours. SIC is shown to increase strength and fracture toughness but these were affected by loading rate. SIC particle sizes of 0.56 to 0.76 pm gave the biggest increases in properties. The finest Sic particles gave the greatest plastic deformation. SINTERING POWDER
H.Masaki et al. (Toyota Research Laboratory, Aichi, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 12, 1996, 1444-1448. (In Japanese.) Sintering of Y-Si-Al-O-N powders, without additives, was investigated during hot pressing. It is reported that the lattice parameters were constant during sintering, indicating that solubility was constant.
HIP SINTERING AND MAGNETIC SATURATION OF IRON NITRIDE
S.Ito et al. (Science University of Tokyo, Tokyo, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 12, 1996, 14151419. (In Japanese.) The decomposition of Fe,N on sintering at 670°C was noted. It was reported that HIP sintering below this temperature had been used to avoid this. Conditions investigated were 450 to 550°C and 50 to 200 MPa for 2 hours. There was decomposition at 550°C. Density of 97% was attained at 550°C and 200 MPa. Magnetic properties were measured and correlated with process conditions. MAGNETIC COBALT
al. (Sumitomo Special Japan.) J. Jpn. Sot. Metall., Vol 43, No 12, (In Japanese.)
Hard materials steels
REACTIVE PLASMA SPRAYING OF COATINGS CONTAINING TITANIUM HARD PHASES SYNTHESIZED IN SITU
L.Zhao et al. (Aachen University of Technology, Aachen, Germany.) Znt. J. Refractory Metals Hard Mater., Vol 15, No 5/6, 1997, 311-315. Coatings of Ti base composites containing carbides and nitrides synthesized in situ were investigated using reactive plasma spraying of Ti powders in CH, and N as reactive gases. Structural analysis showed the presence of carbides and nitrides. The coatings are reported to have good wear and corrosion properties. CHIP MACHINING CARBIDES
M.Kouril et al. (PRAMET A.S., Sumperk, Czech Republic.) Pokroky Praskove Metal., Vol 35, No 2, 1997. 514. (In Czech.) Investigations, aimed at the solution of problems in the use of WC-25%Co cutting tool materials, are described. Conditions and cutting parameters for practical use are suggested. Relationships between wear and cutting conditions are evaluated. Practical use of the results is outlined. CORROSION RESISTANCE OF TITANIUM CARBIDE BASED CERMETS
H.Suzuki et al. (Chiba Inst. of Technology, Narashino, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 11, 1996, 1345-1349. (In Japanese.) Tools for sealing drinks cans are discussed with reference to corrosion by acidic juices and TIC base materials are considered in this application. Use of TX-55wt%(Ni-Cr-Mo) cermets is suggested. The binder was Ni-25wtBMo-3%Xr. This cermet is reported to have high hardness and transverse rupture strength and good corrosion resistance. Properties varied with sintering conditions.
O.Yamashita et Metals, Osaka, Powder Powder 1996, 1449-1454. 44
Applications of Fe-Co alloys are discussed with regard to magnetic properties. Fe-50wt%Co ring samples were prepared from mixed elemental powders, which had been granulated by spray drying with a binder by pressing and sintering. The magnetic properties were reported to be superior to those of Fe-49%Co-2%V.
FORMATION OF TUNGSTEN CARBIDE BY MECHANICAL SOLID STATE REDUCTION
M.S.El-Eskandarany et al. (Al-Azhar University, Cairo, Egypt.) J. Jpn. Sot.
Powder Powder Metall., Vol 43, No 11, 1996, 1368-1373. (In English.) It is reported that nanocrystalline WC had been prepared by high energy ball milling of WO,, Mg and graphite, in Ar. After 24 hours the WO:, had been completely reduced to W metal. At the same time W reacts with C to form WC. After 48 hours the mixture contained only WC and MgO which was removed by chemical leaching. The WC was consolidated in vacuum without binder phase under pressure of 19.6 to 38.2 MPa for five minutes using plasma activated sintering. Density of 99.5% and a grain size of 25 nm were attained. EROSIVE
WEAR OF TUNGSTEN
T.Yamamoto et al. (Dijet Industrial Co, Osaka, Japan.1 J. Jpn. Sot. Powder Powder Metall., Vol 43, No 12, 1996, 1439-1443. (In Japanese.) Erosive wear of WC-Co was investigated as a function of Co content using bombardment with SIC particles, sample weight loss and wear damage profile. Weight loss increased with Co content and decreased with hardness. At 0 to Z.O%Co the weight loss was less than for B,C and SIC at the same hardness. PREPARATION CUTTING
TOOL WITH GRADED
H.Itoh et al. (Centre for Integrated Research in Science and Engineering, Nagoya, Japan.) J. Jpn. Sot. Powder Vol 43, No 12, 1996, Powder Metall., 1455-1460. (In Japanese.) It is reported that diamond coatings had been deposited on S&N, by twostage chemical vapour deposition from CO-H, mixtures. A graded interlayer was prepared before deposition. The coated tool is shown to have a long service in cutting Al-20%Si.
F.Binczyk et al. (Silesian Technical University, Katowice, Poland.) Powder Technol., Vol 94, No 3, 1997, 259-263. It is reported that three-layer composites, substrate, diffusion and sintered layers, had been made from powders prepared by self-disintegration of Fe-36.5wt%Al-1.2r/rC ingots with Fe powder added. The substrate was plain C steel. Hot pressing was used. Bonding was determined by the properties of the sintered and diffusion layers.