Sintering structure and properties of submicron cemented carbide

Sintering structure and properties of submicron cemented carbide

STRUCTURE TWO-PHASE ALLOYS AND PROPERTIES OF NICKEL ALUMINIDE S.Ochiai et al. (Teikyo University of Science and Technology, Yamanashi, Japan.1 J. Jp...

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STRUCTURE TWO-PHASE ALLOYS

AND PROPERTIES OF NICKEL ALUMINIDE

S.Ochiai et al. (Teikyo University of Science and Technology, Yamanashi, Japan.1 J. Jpn. Sot. Powder Powder Metall., Vol 43, No 11, 1996, 1361-1367. (In Japanese.) It is reported that two-phase, NiAlN&Al, intermetallic alloys had been made from mixed elemental powders or from prealloyed NiAl and Ni powders. Mechanical alloying and HIP were used. Alloys made from elemental powders had a fine microstructure and were near full density. Materials made from prealloyed NiAl had higher density which was increased by increased HIP temperature. Structures and mechanical properties are described and compared.

with reduced WC particle size. Dilatometry studies indicated that initial densification was by grain boundary diffusion. The activation energy for sintering was less for finer particle sizes. CEMENTED CARBIDES BASED ON SUBMICRON AND ULTRAFINE POWDERS R.Porat et al. (ISCAR Ltd, Tefen, Israel.) The attainment of a good combination of high toughness and wear resistance in carbide materials was discussed. It was shown that this can be achieved by the use of submicron, 0.5 to 1.0 pm, or ultrafine, 0.1 to 0.5 urn, WC powders. A study of effects of WC grain size, Co content and presence of growth inhibitors was described.

EFFECT OF PALLADIUM ON SINTERING AND TRANSFORMATIONS IN IRON SILICIDE

VALIDITY OF RATE-CONTROLLED SINTERING OF DENSE NANOCRYSTALLINE MATERIALS

K.Hayashi et al. (University of Tokyo, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 12, 1996, 1473-1478. (In Japanese. 1 Synthesis of FeSi,, 8, by peritectoid between FeSi, c, and Fe,%,, o, is discussed with regard to the low reaction rate. It is reported that the reaction is enhanced by a small amount of Pd. Time for sintering to near full density is also reduced.

A.V.Ragulya, V.V.Skorokhod. (Inst. for Problems of Materials Science, Kiev, Ukraine. 1 Rate controlled sintering and its application to dense and fine grained materials was discussed. The method is based on careful study of pore and grain structure evolution during non-isothermal sintering. Recrystallization was shown to occur at densities above 90 to 92% owing to minimization of closed porosity. Studies of TiN-Ni were discussed. Rate controlled and conventionally sintered materials were compared. Relationships between hardness, porosity and sintering method were analysed.

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14TH INTERNATIONAL PLANSEE SEMINAR. The Abstracts which follow are of papers presented at the Seminar, which was held in Reutte, Austria, in May 1997.

NANOSTRUCTURED COMPOSITION OF DIAMOND-TUNGSTEN CARBIDECOBALT

A.Bukov et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) It was reported that diamond-WCCo materials had been produced. The process, starting with scrap hardmetal fragments, was described and involved oxidation, reduction and carburization. Diamond was formed in situ by a highly energetic process. SINTERING STRUCTURE AND PROPERTIES OF SUBMICRON CEMENTED CARBIDE

A.Rosen et al. (Technion, Haifa, Israel.) Effects of initial particle size on sintering structure and properties of WC6%Co, with growth inhibitors VC and Properties Cr,C,,, were investigated. were superior to those of larger grained WC materials. Shrinkage was increased

EFFECT OF SINTERING ATMOSPHERE AND STRUCTURE ON PROPERTIES OF CEMENTED CARBIDES M.Rosso, A.Geminiani. (Politecnico di Torino, Torino, Italy.) Properties of hardmetals were discussed with reference to properties of the constituents and interaction between binder and hardmetal. Adjustment of composition and powder characteristics to meet specified requirements was considered. An investigation of micrograin WC, with addition of TaC and NbC, and of the effects of process conditions was described. It was shown that TaC and NbC inhibit grain growth but increase shrinkage and lower transverse rupture strength. Presintering in cracked NH, was shown to be beneficial. EFFECT OF GROUP III ELEMENTS ABRASION RESISTANCE OF SPUTTERED TITANIUM NITRIDE COATINGS

ON

V.Brozek et al. (Inst. of Chemical Technology, Prague, Czech Republic.)

Investigations into the effects of additions of group III elements on the properties of magnetron sputtered TiNTiC coatings on cemented carbide substrates were described. It is reported that small concentrations of Al or SC improve the structure and increase the hardness. Effects of B and Y were also studied. RESIDUAL STRESSES AND HARDNESS OF TITANIUM NITRIDE COATINGS

H.W.King et al. (University of Victoria, Victoria, Canada. 1 Residual stresses in TIN coatings on 316L stainless steel were measured by an X-ray method in the range 15 to 800°C. At ambient temperature compressive stresses of about 4 GPa were found. These decreased on heating to zero at 5OO”C, which was the temperature of deposition. Stresses were tensile above 500°C reaching about 8 GPa at 800°C. On cooling to room temperature the residual compressive stress was 3 GPa. This was attributed to loss of N and stress relief and was accompanied by a drop in hardness. SYNTHESIS OF SPUTTERING TARGETS AND PROPERTIES OF THIN PHYSICALLY VAPOUR DEPOSITED FILMS

J.J.Moore et al. (Colorado School of Mines, Golden, USA.) Composition and microstructures of thin Ti-B-N, Ti-Si-B-N, Ti-Si-C-N and Ti-Al-C-N films, deposited on high speed steel by sputtering, were investigated. The substrate was sputter cleaned and Ti and TIN interlayers deposited before deposition of the multicomponent film. Orientation relationships between substrate and interlayers were established. Corrosion and oxidation properties of the coatings were studied. USE OF ENERGY FILTERING ELECTRON MICROSCOPY FOR CHEMICAL CHARACTERIZATION HARDMETALS

OF

W.Grogger et al. (Technological University of Graz, Graz, Austria.) The use of transmission electron microscopy for measurement of distribution of elements in metals and alloys, at nanoscale resolution, was discussed. Application of a modified microscope to nanochemical characterization of oxide dispersion strengthened alloys, hardmetals and hardmetal coatings was reported. ROLLING

M.L.Smith University,

OF RHENIUM

METAL

et al. (Loyola Marymount Los Angeles, USA.)

MPR July/August

1998 45