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Development of tough and strong zirconia based composite
The resistance of Ti-G%Al-4%V alloys, with a chemically vapour deposited diamond coating, to solid particle abrasion was compared with materials with physically deposited diamond coatings. The abrasion resistance depended on the CH, content of the deposition gas and 4% gave better abrasion resistance than 1%. PVD coatings had little effect on erosion. The coatings deposited from deposition gases with 1 and 4% CH, differed in failure mechanisms, intergranular and transgranular cracking respectively
7hgsten EFFECT OF NICKEL ACTIVATOR ON DENSITY AND STRUCTURAL DEVELOPMENT IN SINTERED TUNGSTEN A.Radon et al. (Akademia GorniczoHutnicza, Krakow, Poland.) Rudy Metale., Vol43, No 3, 1998,139-144. (In Polish.) Effects of 0.25, 0.5 and lwt% Ni sintering activator on shrinkage and microstructural evolution during sintering of W were investigated. Green compacts of 70% density were sintered at 1050 to 1200°C for 1 to 6 hours.
Hard materials steels
DIAMOND COATINGS FOR SHAFTS DEPOSITED BY INDUCTION PLASMA J.O.Berghaus et al. (McGill University, Montreal, Canada.) Znt. J. Refractory Metals Hard Mater., Vol 16, No 3, 1998, 201-205. Properties of induction plasma torches were discussed with respect to benefits, large area coverage and high deposition rates, in synthesis of diamond layers. Plasma induction deposition of diamond was investigated for growth rates and coating thickness under various conditions without diamond preseeding. A small diameter, 4.76 mm, substrate was used to study diamond quality as a function of position in the much larger diameter plasma. It is shown that gas velocity affects the thickness of the thermal boundary layers and affects the radial diamond growth rate. CHARACTERISTICS OF DC-GLOW DISCHARGE VAPOUR DEPOSITION REACTOR FOR DEPOSITION OF DIAMOND
Ceramic materials
R.Haubner Technology,
PROPERTIES OF ALUMINACHROMIUM NANOCOMPOSITE MADE BY MECHANO-SYNTHESIS
Refractory
A.Mocellin et al. (Laboratory for Metallic Materials, E.M.N., Nancy, France.) Powder Technol., Vol 98, No 3, 1998,257-263. It is reported the A&O,-Cr nanocomposite powders had been prepared by high energy milling. Powder characteristics were determined and correlated with process conditions. It was shown that Cr could be dissolved in the powders if handled in acidic or alkaline conditions and therefore required handling in neutral liquids. DEVELOPMENT OF TOUGH AND STRONG ZIRCONLA BASED COMPOSITE T.Sekino et al. (Matsushita Electric Works Ltd, Kadoma, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 1, 1998,3-12. (In Japanese.) A novel concept in composite ceramic design, interpenetrated intergranular nanostructure, is described. This comprises pm sized particles of one compound reinforced with nm particles of a second compound together with pm particles of the second reinforced with nm particles of the first. This concept has been applied to ZrO, based composites for which structures and properties are described.
and tool
et
(University of Austria.) Znt. J. Hard Mater., Vol 16,
aZ.
Vienna,
Metals
No 3, 1998,207-216. It is reported that diamond films, up to 0.55 mm thick, had been deposited on MO substrates by pulsed DC glow discharge chemical vapour deposition at growth rates up to 30 pm per hour. The films are shown to be crystalline and of high purity. Effects of process conditions, at a constant power input of 6 kW, on characteristics of deposits are described. Suggested applications are tool tips, heat sinks and infrared windows. EFFECT AND MECHANISM OF TITANIUM OXIDE ON GRAIN REFINEMENT OF AMORPHOUS SILICON NITRIDE CKawai et al. (Sumitomo Electric Industries, Itami, Japan,) J. Jpn Sot. Powder Powder Metal, Vol 44, No 10, 1997,963-969. (In Japanese.) Compacts of amorphous S&N,-TiO, were heated at 1490°C for l-10 hours under N pressures of 0.92 to 1000 atmospheres to investigate the effects of pressure on grain structure and the role of TiO, in the grain refining mechanism. Thermodynamics was used to show that high pressure inhibits formation of SiO and allows further synthesis of S&N,. Crystalline phases, cxSisN4, Si,N,O and TiN, were detected after heating. The high pressure enhanced grain refinement.
PRESSURELESS SINTERING AND EVALUATION OF SILICON CARBIDEBORON CARBIDE COMPOSITES K.Nihara et al. (Osaka University, Ibaraki, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, No 12, 1997, 1078-1082. (In Japanese.) Pressureless sintering of Sic-B,C composites was investigated. It is reported that near full density was attained after sintering at 2250 to 23OO”C, in Ar, for 1 hour. From electron microscopy it is deduced that B,C dispersed in the SIC inhibited grain growth. At up to 10~01% B,C the SIC matrix had rod-like grains which became rounded and equiaxed at 20~01% B,C. There were no matrix-B,C interfaces. STRUCTURE AND PROPERTIES OF SINTERED SILICON NITRIDETITANIUM NITRIDE MATERLALS KKishi et al. (Kyushu National Industrial Research Inst., Tosu, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 1, 1998,25-30. (In English.) It is reported that SisN, and Si,N,TiN had been prepared by a vapour phase reaction method and hot pressing to investigate the effects of TIN on the structure and properties of the sintered materials. Hot pressing was at 1800 to 1850°C in N with additions of Also, and Y,O, as sintering aids. At 1800°C SisN, had a fine grained structure. Rod-like grains grew at 1850°C and there was an increase in fracture toughness. In Si,N,TiN rods grew at 1800°C indicating that this is enhanced by TiN. The S&N,-TIN composite is reported to have high fracture toughness. SYNTHESIS OF ALUMINIUM NITRIDE FROM A UREA PRECURSOR K.Uheda et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 1, 1998, 3135. (In Japanese.) Synthesis of AlN from urea, CO(NH,),, and AlCl, is described. AlCl, is introduced into molten urea, at 135”C, under non-aqueous conditions, to make an intermediate, which is pyrolysed at 900°C in N, to yield AlN, without formation of A&O,. The AlN was crystalline. Yield was about 80% of stoichiometric due to loss of Al by formation of a volatile Al compound. The powder was in 30 pm aggregates made up of 1 pm particles. The process is discussed.
Intermetallic
materials
PULSE CURRENT PRESSURE SINTERING OF MECHANICALLY ALLOYED NIOBIUM ALUMINIDE POWDER
MPR May 1999 39
7hgsten EFFECT OF NICKEL ACTIVATOR ON DENSITY AND STRUCTURAL DEVELOPMENT IN SINTERED TUNGSTEN A.Radon et al. (Akademia GorniczoHutnicza, Krakow, Poland.) Rudy Metale., Vol43, No 3, 1998,139-144. (In Polish.) Effects of 0.25, 0.5 and lwt% Ni sintering activator on shrinkage and microstructural evolution during sintering of W were investigated. Green compacts of 70% density were sintered at 1050 to 1200°C for 1 to 6 hours.
Hard materials steels
DIAMOND COATINGS FOR SHAFTS DEPOSITED BY INDUCTION PLASMA J.O.Berghaus et al. (McGill University, Montreal, Canada.) Znt. J. Refractory Metals Hard Mater., Vol 16, No 3, 1998, 201-205. Properties of induction plasma torches were discussed with respect to benefits, large area coverage and high deposition rates, in synthesis of diamond layers. Plasma induction deposition of diamond was investigated for growth rates and coating thickness under various conditions without diamond preseeding. A small diameter, 4.76 mm, substrate was used to study diamond quality as a function of position in the much larger diameter plasma. It is shown that gas velocity affects the thickness of the thermal boundary layers and affects the radial diamond growth rate. CHARACTERISTICS OF DC-GLOW DISCHARGE VAPOUR DEPOSITION REACTOR FOR DEPOSITION OF DIAMOND
Ceramic materials
R.Haubner Technology,
PROPERTIES OF ALUMINACHROMIUM NANOCOMPOSITE MADE BY MECHANO-SYNTHESIS
Refractory
A.Mocellin et al. (Laboratory for Metallic Materials, E.M.N., Nancy, France.) Powder Technol., Vol 98, No 3, 1998,257-263. It is reported the A&O,-Cr nanocomposite powders had been prepared by high energy milling. Powder characteristics were determined and correlated with process conditions. It was shown that Cr could be dissolved in the powders if handled in acidic or alkaline conditions and therefore required handling in neutral liquids. DEVELOPMENT OF TOUGH AND STRONG ZIRCONLA BASED COMPOSITE T.Sekino et al. (Matsushita Electric Works Ltd, Kadoma, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 1, 1998,3-12. (In Japanese.) A novel concept in composite ceramic design, interpenetrated intergranular nanostructure, is described. This comprises pm sized particles of one compound reinforced with nm particles of a second compound together with pm particles of the second reinforced with nm particles of the first. This concept has been applied to ZrO, based composites for which structures and properties are described.
and tool
et
(University of Austria.) Znt. J. Hard Mater., Vol 16,
aZ.
Vienna,
Metals
No 3, 1998,207-216. It is reported that diamond films, up to 0.55 mm thick, had been deposited on MO substrates by pulsed DC glow discharge chemical vapour deposition at growth rates up to 30 pm per hour. The films are shown to be crystalline and of high purity. Effects of process conditions, at a constant power input of 6 kW, on characteristics of deposits are described. Suggested applications are tool tips, heat sinks and infrared windows. EFFECT AND MECHANISM OF TITANIUM OXIDE ON GRAIN REFINEMENT OF AMORPHOUS SILICON NITRIDE CKawai et al. (Sumitomo Electric Industries, Itami, Japan,) J. Jpn Sot. Powder Powder Metal, Vol 44, No 10, 1997,963-969. (In Japanese.) Compacts of amorphous S&N,-TiO, were heated at 1490°C for l-10 hours under N pressures of 0.92 to 1000 atmospheres to investigate the effects of pressure on grain structure and the role of TiO, in the grain refining mechanism. Thermodynamics was used to show that high pressure inhibits formation of SiO and allows further synthesis of S&N,. Crystalline phases, cxSisN4, Si,N,O and TiN, were detected after heating. The high pressure enhanced grain refinement.
PRESSURELESS SINTERING AND EVALUATION OF SILICON CARBIDEBORON CARBIDE COMPOSITES K.Nihara et al. (Osaka University, Ibaraki, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, No 12, 1997, 1078-1082. (In Japanese.) Pressureless sintering of Sic-B,C composites was investigated. It is reported that near full density was attained after sintering at 2250 to 23OO”C, in Ar, for 1 hour. From electron microscopy it is deduced that B,C dispersed in the SIC inhibited grain growth. At up to 10~01% B,C the SIC matrix had rod-like grains which became rounded and equiaxed at 20~01% B,C. There were no matrix-B,C interfaces. STRUCTURE AND PROPERTIES OF SINTERED SILICON NITRIDETITANIUM NITRIDE MATERLALS KKishi et al. (Kyushu National Industrial Research Inst., Tosu, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 1, 1998,25-30. (In English.) It is reported that SisN, and Si,N,TiN had been prepared by a vapour phase reaction method and hot pressing to investigate the effects of TIN on the structure and properties of the sintered materials. Hot pressing was at 1800 to 1850°C in N with additions of Also, and Y,O, as sintering aids. At 1800°C SisN, had a fine grained structure. Rod-like grains grew at 1850°C and there was an increase in fracture toughness. In Si,N,TiN rods grew at 1800°C indicating that this is enhanced by TiN. The S&N,-TIN composite is reported to have high fracture toughness. SYNTHESIS OF ALUMINIUM NITRIDE FROM A UREA PRECURSOR K.Uheda et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 1, 1998, 3135. (In Japanese.) Synthesis of AlN from urea, CO(NH,),, and AlCl, is described. AlCl, is introduced into molten urea, at 135”C, under non-aqueous conditions, to make an intermediate, which is pyrolysed at 900°C in N, to yield AlN, without formation of A&O,. The AlN was crystalline. Yield was about 80% of stoichiometric due to loss of Al by formation of a volatile Al compound. The powder was in 30 pm aggregates made up of 1 pm particles. The process is discussed.
Intermetallic
materials
PULSE CURRENT PRESSURE SINTERING OF MECHANICALLY ALLOYED NIOBIUM ALUMINIDE POWDER
MPR May 1999 39