of ZrO, toughness controlled tetragonal
for maximum fracture was 10%. Toughness was by transformation to the form.
EFFECT OF ADDITIONS OF MAGNESIA ON PLATELIKE GROWTH IN SINTERED ALUMINA AND PROPERTIES
A.Tsukuda et al. (Kagawa Industrial Technology Centre, Takamatsu, Japan.) J. Jpn Sot. Powder Powder Metall.,Vol 45, No 11, 1998, 1018-1023. (In Japanese.) Effects of additions of MgO on growth of platelike particles in Also, and on properties were investigated. The presence of the platelike particles is shown to increase fracture toughness. The increase is attributed to a crack deflection mechanism.
EFFECTS OF COPPER PLATED SILICON CARBIDE PARTICLES ON PROPERTIES OF COPPER-SILICON CARBIDE
Y.F.Lee et al. (National Central University, Chung-Li, Taiwan.) Powder Metall., Vol42, No 2, 1999, 147-152. The effect of Cu plated SIC particles in hot pressed Cu-(50 to 8O)vol % SIC particle composites, on densification and properties, was investigated. The Cu coating was deposited by electroless plating. Properties of the composites were summarized with regard to %SiC. Two fracture models are identified: one is cracking at the Cu-Sic interface and the other is pulling out of the particles. The strength of the interface and hot pressing temperature are shown to be the main factors controlling fracture. The presence of the Cu plating improved the properties.
MAGNETIC PROPERTIES OF ‘SENDUST’ ALLOYS MADE FROM SPRAY DRIED GRANULATED POWDERS
Y.Kishimoto et al. (Sumitomo Metal Industries Co Ltd, Amagaski, Japan.) J.
Jpn Sot. Powder Powder Metall.,Vol 45, No 11,1998,1036-1041. (In Japanese.) Applications of Sendust, Fe-Si-Al, alloys are reviewed with respect to properties. The magnetic characteristics of Sendust rings, made from spray dried granulated powders, were investigated. Processing is described. It is shown that the method is suitable for making parts to near net shape.
38 MPR March 2000
Hard materials steels
ANALYSIS OF DIE COMPACTION TUNGSTEN CARBIDE-COBALT POWDER MIXTURES
SRoure et al. (Federal Mogul Sintered Products, Le Pont de Claix, France.) Powder Metall., Vol42, No 2, 1999, 164170. Die compaction of a range of WC-Co powders was investigated using an instrumented industrial ‘press. Upper and lower punch forces, radial die stress and frictional shearing at the powder die-wall interface were determined. Data from the powders was analysed to provide intrinsic stress/density compressibility relationships and the powder/die coefficient of friction. Material and process parameters are discussed. HIGH TEMPERATURE FATIGUE CEMENTED CARBIDES UNDER CYCLIC LOADS
P.Kindermann et al. (University of Erlangen-Nurnberg, Erlangen, Germany.) Int. J. Refractory Metals Hard Mater., Vol 17, No l-3,1999,55-68. Properties, at 25 to 900°C in air, of WC-Gwt%Co and a Ti(C,N) cermet, were investigated under a range of loading conditions including cyclic. Temperature dependent fatigue effects were found by electron microscopy. The Co matrix was affected by the face centred cubic to close packed hexagonal transition. At higher temperatures, oxidation of the binder and a brittle to ductile transition in the hard phases were significant. FRICTION AND WEAR OF SUPERHARD MATERIALS
E.J.Brookes Hull, UK.)
et al. (University Iat. J. Refractory
Metals Hard Mater., Vol 17, No l-3, 1999, 69-77.
Friction and wear of a number of superhard materials were investigated by pin-on-disc tests. These were between like and unlike pairs of materials. In cases where there was a difference in hardness the slider was usually softer than the test sample. Sliding was accompanied by a slip-stick motion. POTENTIAL OF A COMPOSITE WITH TOUGHNESS AND RESISTANCE TO PLASTIC DEFORMATION
T.Viatte et al. (Teledyne Metalworking Products, LaVergne, USA.) Int. J. Refractory Metals Hard Mater., Vol 17, No l-3,1999, 79-89. Mechanical and microstructural studies of materials ranging in
composition from Ti(C,N)-Mo,C-Ni through to WC-Co are described. Structures and properties were correlated. Image analysis was used to measure microstructural parameters. Some of the hybrid materials had fine structures with high contiguity giving high hardness and good high temperature mechanical properties. INFLUENCE OF VANADIUM CARBIDE ON STRUCTURE AND PROPERTIES OF TUNGSTEN CARBIDE-COBALT
F.Arenas et al. (University Inst. of Technology, Caracas, Venezuela.) Int. J. Refractory Metals Hard Mater., Vol 17, No 1-3, 1999,91-97. Investigations of structure and properties of WC-(0. 18, 36, 56, 72 and 90)wt%VC-10%Co are described. Structural parameters measured were contiguity, binder mean free path, carbide grain size and the phases present. Addition of VC inhibited formation of the brittle n(W,Co)C phase. Alloy composition required care in selection to give adequate toughness, of 18 MPa.ml”, coupled with higher hardness. NICKEL-BORON COATED TUNGSTEN AND VANADIUM CARBIDE POWDERS FOR LIQUID PHASE SINTERING
M.VBlez et al. Bolivar (Simon University, Caracas, Venezeula.) Ink. J. Refractory Metals Hard Mater., Vol 17, No l-3,1999,99-102. It is reported that WC and VC powders had been coated with Ni-B, by an electroless process. The coated powders were heated at 400 to 12OO”C, which- crystallized the coating. The powders were mixed with 2% PVA binder, pressed and sintered. When sintering the VC material the liquid phase migrated to the outside of the compact, adversely affecting densification. Sintering WC-Ni-B at 1035 to 1100°C avoided this and gave densities of 91 to 93%.
SYNTHESIS OF TITANIUM SILICIDE BY MECHANICAL ALLOYING AND PRESSURE SINTERING
T.Ogitsu, K.Isonishi. (Shiga University, Ohtsu, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 10, 1998, 1000-1006. (In Japanese.) Ti-375at%Si was mechanically alloyed to give stoichiometric Ti,Si,. T&S& did not form during MA, except after long milling times and heat treatment. After short times and heat treatment TiSi and TiSi, formed in addition to Ti,Si,. Hot pressing gave densities up to 99.7%, Vickers hardness