- Email: [email protected]
Microstructure and sintering of tungsten carbide-copper composites
Molybdenum A study of carburized molybdenumlanthanum cathode material C.Yao et al. (Aerospace Research Inst. for Materials and Technology, Beijing, China,) Int. J. Refractory Metals/Hard Materials, Vo118, No 6, 2000, 261.265. The effects of carburizing on the thermionic emission properties of Mo doped with LazO3 were investigated to optimize process conditions. Carburizing was by exposure to C6H 6 vapour at 8.5 to 9.5 Pa pressure and 1500 °C for 8 minutes. Emission properties were similar to W-ThO 2. The possibility of replacing this radioactive material in electron tubes is considered.
Ceramic materials Effects of process conditions on properties of alumina made by centrifugal compaction H.Y.Suzuki et al. (Hiroshima University, HigashiHiroshima, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 5, 2000, 465-473. (In Japanese.) A120 3 compacts were prepared from a slurry by high speed centrifugal compaction, dried and sintered in dry H or by HIP. The object was elimination of pores. HIP samples were almost free of pores, were translucent and had a bend strength of 750 MPa. Annealing in air caused pores to form with loss of translucence.
Composite materials Powder injection moulding of alumina-titanium carbide composites H.Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 5, 2000, 507-509. (In Japanese.) It is reported that AI203-'l-iC cutting tools had been made by PM methods. Injection moulding was used to assess the feasibility of using this process. Structures and properties were examined with reference to process conditions to optimize processing for good service performance.
Microstructure and sintering of tungsten carbide-copper composites Z.Wang et al. (Tianjin University, T'eanjin, China.) PM Technology, Vol 18, No 4, 2000, 265-269. (In Chinese.) Effects of %WC and sintering temperature and time on structural evolution in WC-Cu composites were investigated. Shrinkage was low, WC inhibited sintering and grain growth. Four stages in the sintering process were identified.
Hard materials and tool steels Functionally graded hardmetals K.Tsuda et al. (Sumitomo Electric Industries Ltd, Itami, Japan.) J. Jpn Soc.Powder/powderMetall., Vol 47, No 5, 2000, 487-495. (In Japanese.)
42
MPR October 2ool
Development of a graded hardmetal, comprising a Ti based ceramic surface layer, a hard cemented carbonitride core and graded intermediate layers, is described. Conditions leading to tool damage were investigated using temperature distribution measurements to determine tool temperatures. Stress distributions are considered. The graded tool materials are reported to show improved performance.
Synthesis of tungsten and molybdenum mono-carbonitrides N.Asada et al. (Tokyo Tungsten Co Ltd, Toyama, Japan.) J. Jpn Soc.Powder/Powder Metall., Vol 47, No 5, 2000, 496.501. (In English.) It is reported that W(C,N), with 1 to 20at%N, had been synthesized by heating WC mixtures in N at 10 to 160 MPa and 1250 to 1400 °C. W(C,N) with 5%N was made by heating in CH4-NH 3 at 1300 °C. Mo(C,N) with 14 to 25at%N was also synthesized. MoN was not synthesized.
Production of cemented carbide with iron-aluminium binder phase M.Fukunaga et al. (MMC Kobelco Tool Co Ltd, Akashi, Japan.) J. Jpn Soc. Powder/powderMetall., Vo147, No 5, 2000, 510-514. (In Japanese.) Studies of structures and properties of a WC10wt% binder phase, Fe-AI or Fe-A1-B, made by pulsed current sintering, are described. B is shown to increase density and hardness. Contamination with O was detrimental, the binder with B oxidized at higher temperatures than conventional WC-Co WC-(Fe-A1-B) had high oxidation resistance at 765 °C.
Particle erosion and microstructure of mechanically alloyed iron-chromium-carbon S.Takaki et al. (Kyusyu University, Kyusyu, Japan.) J. Jpn Soc. Powder/PowderMetall., Vol 47, No 5, 2000, 510-514. (In Japanese.) Elemental Fe-Cr-C powders were mechanically alloyed in Ar for 200 hours and hot pressed at 1000 °C for 3 hours. The structure comprised an 0tFe based phase with M23C 6 carbides. Fe-50wt%Cr-4.8%C was evaluated for erosive wear and is reported to be better than 9%Cr-1%Mo steel with high wear resistance at medium and high impingement angles.
Sintering of molybdenum-nickel boride base hardmetals Y.Yamasaki et al. (Toyo Kohan Co Lid, Kndamatsu, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 5, 2000, 521-525. (In Japanese.) Liquid phase sintering of three Mo-Ni-B alloys was investigated with regard to mechanisms and structural evolution. Mo2NiB 2 may be either tetragonal or orthorhombic depending on alloy composition and process temperature. The orthorhombic form is synthesized by a solid state reaction prior to formation of a quasi-eutectic liquid phase, which gives full
densification. The orthorhombic phase transforms to tetragonal at increased temperature. This is enhanced by addition of Cr and/or V.
Refractory metals Oxidation of refractory metals in air and oxygen at low pressure J.R.DiStefano et al. (Oak Ridge National Laboratory, USA.) Int. J. Refractory Metals/Hard Materials, Vol 18, No 4-5, 2000, 237-243. Oxidation rates and effects of oxidation on mechanical properties of selected V, Nb, Ta and Mo alloys, oxidized in air and O at low pressure, were investigated. It is reported that none of the alloys tested developed protective surface oxide films. Oxidation behaviour and mechanical properties depended on whether external films formed, O dissolved or if there was internal oxidation. Data is presented for oxidation rates, structural evolution and mechanical properties.
Ordering in B2 ternary alloys S.Amancherla et al. (Oak Ridge National Laboratory, USA.) Int. J. Refractory Metals/Hard Materials, Vol 18, No 4-5, 2000, 245-252. Prediction of ordering in B2 alloys, based on Nb-'l-i-A1 and Fe-Ni-A1, was discussed and compared with experimental results. Prediction of ordering was based on the Bmgg and Williams theory of order/disorder. Experimentally, ordering was studied by measurement of sub-lattice compositions using a micro-analysis technique. The predictions are shown to be usefully accurate.
Creep of refractory metal alloys R. W.Buckman. (Refractory Metals Technology, Pittsburgh, USA.) Int. J. Refractory Metals/Hard Materials, Vo118, No 4-5, 2000, 253-257. Creep of Nb, Ta and Mo alloys, under uniaxial and biaxial loading, was investigated at 40 to 50% of the melting point. It is shown that results are influenced by test conditions as well as material parameters. Nb-I%Zr-0.1%C, made by plasma arc melting, showed unexpectedly low creep strength.
Mechanical alloying Amorphization in aluminium-nickelzirconium R. Tsuzuki, E.Yuasa. (Musashi Inst. of Technology Tokyo, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 4, 2000, 400-405. (In Japanese.) A n investigation of mechanical alloying of binary and ternary A1-N-Zr mixtures is described. There was amorphization in Al-(40 to 50)at%Zr, Ni-(35 to 60)%Zr and the ternary mixture. The ternary mixture was more effectively amorphized by mixing milled amorphous binary mixtures followed by further milling. Hardness of the powders was increased by increases in Ni:Zr and AI:(Ni,Zr) ratios.
www.metal-powder.net
Ceramic materials Effects of process conditions on properties of alumina made by centrifugal compaction H.Y.Suzuki et al. (Hiroshima University, HigashiHiroshima, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 5, 2000, 465-473. (In Japanese.) A120 3 compacts were prepared from a slurry by high speed centrifugal compaction, dried and sintered in dry H or by HIP. The object was elimination of pores. HIP samples were almost free of pores, were translucent and had a bend strength of 750 MPa. Annealing in air caused pores to form with loss of translucence.
Composite materials Powder injection moulding of alumina-titanium carbide composites H.Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 5, 2000, 507-509. (In Japanese.) It is reported that AI203-'l-iC cutting tools had been made by PM methods. Injection moulding was used to assess the feasibility of using this process. Structures and properties were examined with reference to process conditions to optimize processing for good service performance.
Microstructure and sintering of tungsten carbide-copper composites Z.Wang et al. (Tianjin University, T'eanjin, China.) PM Technology, Vol 18, No 4, 2000, 265-269. (In Chinese.) Effects of %WC and sintering temperature and time on structural evolution in WC-Cu composites were investigated. Shrinkage was low, WC inhibited sintering and grain growth. Four stages in the sintering process were identified.
Hard materials and tool steels Functionally graded hardmetals K.Tsuda et al. (Sumitomo Electric Industries Ltd, Itami, Japan.) J. Jpn Soc.Powder/powderMetall., Vol 47, No 5, 2000, 487-495. (In Japanese.)
42
MPR October 2ool
Development of a graded hardmetal, comprising a Ti based ceramic surface layer, a hard cemented carbonitride core and graded intermediate layers, is described. Conditions leading to tool damage were investigated using temperature distribution measurements to determine tool temperatures. Stress distributions are considered. The graded tool materials are reported to show improved performance.
Synthesis of tungsten and molybdenum mono-carbonitrides N.Asada et al. (Tokyo Tungsten Co Ltd, Toyama, Japan.) J. Jpn Soc.Powder/Powder Metall., Vol 47, No 5, 2000, 496.501. (In English.) It is reported that W(C,N), with 1 to 20at%N, had been synthesized by heating WC mixtures in N at 10 to 160 MPa and 1250 to 1400 °C. W(C,N) with 5%N was made by heating in CH4-NH 3 at 1300 °C. Mo(C,N) with 14 to 25at%N was also synthesized. MoN was not synthesized.
Production of cemented carbide with iron-aluminium binder phase M.Fukunaga et al. (MMC Kobelco Tool Co Ltd, Akashi, Japan.) J. Jpn Soc. Powder/powderMetall., Vo147, No 5, 2000, 510-514. (In Japanese.) Studies of structures and properties of a WC10wt% binder phase, Fe-AI or Fe-A1-B, made by pulsed current sintering, are described. B is shown to increase density and hardness. Contamination with O was detrimental, the binder with B oxidized at higher temperatures than conventional WC-Co WC-(Fe-A1-B) had high oxidation resistance at 765 °C.
Particle erosion and microstructure of mechanically alloyed iron-chromium-carbon S.Takaki et al. (Kyusyu University, Kyusyu, Japan.) J. Jpn Soc. Powder/PowderMetall., Vol 47, No 5, 2000, 510-514. (In Japanese.) Elemental Fe-Cr-C powders were mechanically alloyed in Ar for 200 hours and hot pressed at 1000 °C for 3 hours. The structure comprised an 0tFe based phase with M23C 6 carbides. Fe-50wt%Cr-4.8%C was evaluated for erosive wear and is reported to be better than 9%Cr-1%Mo steel with high wear resistance at medium and high impingement angles.
Sintering of molybdenum-nickel boride base hardmetals Y.Yamasaki et al. (Toyo Kohan Co Lid, Kndamatsu, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 5, 2000, 521-525. (In Japanese.) Liquid phase sintering of three Mo-Ni-B alloys was investigated with regard to mechanisms and structural evolution. Mo2NiB 2 may be either tetragonal or orthorhombic depending on alloy composition and process temperature. The orthorhombic form is synthesized by a solid state reaction prior to formation of a quasi-eutectic liquid phase, which gives full
densification. The orthorhombic phase transforms to tetragonal at increased temperature. This is enhanced by addition of Cr and/or V.
Refractory metals Oxidation of refractory metals in air and oxygen at low pressure J.R.DiStefano et al. (Oak Ridge National Laboratory, USA.) Int. J. Refractory Metals/Hard Materials, Vol 18, No 4-5, 2000, 237-243. Oxidation rates and effects of oxidation on mechanical properties of selected V, Nb, Ta and Mo alloys, oxidized in air and O at low pressure, were investigated. It is reported that none of the alloys tested developed protective surface oxide films. Oxidation behaviour and mechanical properties depended on whether external films formed, O dissolved or if there was internal oxidation. Data is presented for oxidation rates, structural evolution and mechanical properties.
Ordering in B2 ternary alloys S.Amancherla et al. (Oak Ridge National Laboratory, USA.) Int. J. Refractory Metals/Hard Materials, Vol 18, No 4-5, 2000, 245-252. Prediction of ordering in B2 alloys, based on Nb-'l-i-A1 and Fe-Ni-A1, was discussed and compared with experimental results. Prediction of ordering was based on the Bmgg and Williams theory of order/disorder. Experimentally, ordering was studied by measurement of sub-lattice compositions using a micro-analysis technique. The predictions are shown to be usefully accurate.
Creep of refractory metal alloys R. W.Buckman. (Refractory Metals Technology, Pittsburgh, USA.) Int. J. Refractory Metals/Hard Materials, Vo118, No 4-5, 2000, 253-257. Creep of Nb, Ta and Mo alloys, under uniaxial and biaxial loading, was investigated at 40 to 50% of the melting point. It is shown that results are influenced by test conditions as well as material parameters. Nb-I%Zr-0.1%C, made by plasma arc melting, showed unexpectedly low creep strength.
Mechanical alloying Amorphization in aluminium-nickelzirconium R. Tsuzuki, E.Yuasa. (Musashi Inst. of Technology Tokyo, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 4, 2000, 400-405. (In Japanese.) A n investigation of mechanical alloying of binary and ternary A1-N-Zr mixtures is described. There was amorphization in Al-(40 to 50)at%Zr, Ni-(35 to 60)%Zr and the ternary mixture. The ternary mixture was more effectively amorphized by mixing milled amorphous binary mixtures followed by further milling. Hardness of the powders was increased by increases in Ni:Zr and AI:(Ni,Zr) ratios.
www.metal-powder.net