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Photochemical synthesis of molybdenum carbide for molybdenum and carbon powders
CORROSION OF TUNGSTEN CARBIDE-NICKEL-CHROMIUMIN SODIUM HYDROXIDE SOLUTION Y.Hayashi et al. (Kyushu University, Fukuoka, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 4, 1999,402-408. (In Japanese.) An investigation of corrosion of WCNi-Cr in 1N NaOH solution, by immersion and electrochemical tests is described. In immersion most of the dissolved metal is W, higher at lower %C and lower CrzC,. This is the reverse to acid and neutral solutions. In polarization tests %C was not significant. There was no passivation and corrosion current density decreased with increase in %C and %Cr,C,. Differences are attributed to variations in the %W dissolved in the binder phase. CORROSION OF TITANIUM CARBIDE IN SINTERED !I’ITANIUM CARBIDE-MOLYBDENUM-TITANIUM ALLOYS Y.Hayashi et al. (Kyushu University, Fukuoka, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 4, 1999,409-416. (In Japanese.) Corrosion of Tic, non-stoichiometric Tic (c.s5and0,,5) and the TiC phase in Ti20wt%Mo-33%TiC samples made by PM was investigated by immersion and electrochemical tests. Corrosion resistance is reported to be good in 33%HCl and 3%NaCl solutions. Corrosion was greater in 5%HNO, due to dissolution of Tic. Corrosion of the alloy in HCl and NaCl was due to loss of PTi. STRU!I’UREOF MULTI-LAYER ALUMINA-TITANIUM-NITROGEN/ CARBON COATINGS ON CEMENTED CARBIDES T.Ishii et al. ( Hitachi Metals Ltd, Kumagaya, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 4, 1999,422-426. (In Japanese.) Microstructures of c&1,0,-Ti(C,N)TiN-substrate, cemented carbide cutting tools was investigated. It is shown that the binding layer contains Ti, C, N, and 0 or Ti, C and 0 and that there is crystallographic continuity between grains. Perpendicular projections were found on the surface of the interlayer. These aided adhesion of the Al,O, layer. A crystallographic model is described. EFFECTS OF MOLYBDENUM CONTENT ON SINTERED TITANIUM-MOLYBDENUM-TITANIUM CARBIDE K.Tokumoto et al. (Nippon Tungsten Co Ltd, Saga, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 6, 1999,573-578. (In Japanese.) 46 MPR November 2000
Microstructures and mechanical properties of sintered Ti-(up to 27)vol%Mo-47.4%TiC were investigated. 97% density was attained in Ti-(2.6 to 16.4)%Mo-TiC alloys. a and 8 Ti based phases and TiC were found according to composition. Hardness and transverse rupture strength were affected by %Mo. Ti-(2.6 to 8.5)%Mo-47%TiC are considered to have good corrosion resistance and a useful combination of mechanical properties. POROSITY IN SPRAY DEPOSITED TOOL STEEL E.J.Lavernia et al. (University of California, Irvine, USA.) Int. J. Powder Metall., Vo125, No 2, 1999,47-55. Porosity in spray formed A2 tool steel was investigated and a heuristic model constructed. The model incorporates fluid flow and solidification. Two regimes, fast flow and rapid solidification, are identified. Porosity is expressed as a function of particle size distribution. Effects of process variables on porosity were studied with the object of minimizing porosity under optimum process conditions. HIGH PRESSURE AND TEMFERATURE SYNTIIESISOF DIAMOND WITII NON-METALLICCATALYST H.Sumiya, S.Satoh. (Sumitomo Electric Ind., Hyogo, Japan.) Int. J. Refract. MetalslHard Mater., Vol 17, No 5, 1999, 345-350. It is noted that oxides of Fe with Ti, Si or Y are effective catalysts for synthesis of diamond at high pressures and temperatures and also enhance sintering in production of polycrystalline diamond. It is reported that polycrystalline diamond could be sintered at 1850 “C to high hardness and good heat resistance.
DEPENDENCE OF HARDNESS ON TEMPERATURE AND POROSITY OF SILICON CARBIDE CERAMICS Y.V.Milman et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Int. J. Refract. MetalslHard Mater., Vol 17, No 5,1999,361-368. The effects of temperature, 20 to 900 “C, and porosity, 0,5,16 or 20%, on Vickers microhardness of Sic ceramics were investigated. Athermal regions of hardness were detected at low temperatures, which are attributed to fracturing and not to plastic deformation, which occurs at higher temperatures. A relationship between hardness and porosity is given. Increase in porosity reduced fracture toughness. Temperature dependence of hardness, where there is high Peierls-Nabarro stress, is expressed diagrammatically, hardness being determined by plastic deformation, brittle fracture and phase transformations. TESTING OF COATED CEMENTED CARBIDES WITH TOUGH SURFACE LAYER J.Spacil. (Pramet Tools s.r.o., Sumperk, Czech Republic.) Pokroky Pras. Metal, Vol37, No 2,1999,45-54. (In Czech.) Testing of cemented carbide cutting tools, with tough and hard coatings, is discussed. Tests were carried out on tools with consideration of wear resistance, toughness and thermal stability. Samples studied included functionally gradient substrates and a range of coatings. Comparison is made with conventional materials. The new materials are shown to perform well, in a wide range of conditions, except in heavy cutting and fine finish cutting.
Hot
isostatic
pressing
PHOTOCHEMICAL SYNTHESIS OF _ MOLYBDENUMCARBIDE FOR MOLYBDENUMAND CARBON POWDERS
COST EFFECTIVE HOT ISOSTATIC PRESSING
N.Shohoju et al. (INETI, Lisbon, Portugal.) Int. J. Refract. MetalslHard Mater., Vol17, No 5,1999,351-356. Polymorphism in stoichiometric and non-stoichiometric MO carbides is described. Up to 1190 “C! the stable phase is orthohrombic clMo,C, between 1190 “C and 1655 “C hexagonal PMo,C is stable. Above 1655 “C a non-stoichiometric MO-C phase exists, hexagonal up to 1960 “C and face centred cubic between 1960 and the melting point, 2580 “C. Heating MO and C in a solar furnace at 1600 “C! resulted in synthesis of non-stoichiometic hexagonal MoC,,,, in 30 minutes. It is suggested that there is a photochemical reaction.
J.Westerlund et al. (ABB Pressure Systems AB, Vasteras, Sweden.) ht. J. Powder Metall., Vol 25, No 3, 1999, 31-35. Development of HIP as a viable production process is discussed. Development of equipment for HIP is reviewed with consideration of efficient production and the need for uniform rapid cooling. Comparison is made of the production requirements of different materials. It is shown that advances in processes can improve efficiency even though the initial costs are high. It is predicted that advances in technology will lead to lower costs and higher throughput of parts.
Microstructures and mechanical properties of sintered Ti-(up to 27)vol%Mo-47.4%TiC were investigated. 97% density was attained in Ti-(2.6 to 16.4)%Mo-TiC alloys. a and 8 Ti based phases and TiC were found according to composition. Hardness and transverse rupture strength were affected by %Mo. Ti-(2.6 to 8.5)%Mo-47%TiC are considered to have good corrosion resistance and a useful combination of mechanical properties. POROSITY IN SPRAY DEPOSITED TOOL STEEL E.J.Lavernia et al. (University of California, Irvine, USA.) Int. J. Powder Metall., Vo125, No 2, 1999,47-55. Porosity in spray formed A2 tool steel was investigated and a heuristic model constructed. The model incorporates fluid flow and solidification. Two regimes, fast flow and rapid solidification, are identified. Porosity is expressed as a function of particle size distribution. Effects of process variables on porosity were studied with the object of minimizing porosity under optimum process conditions. HIGH PRESSURE AND TEMFERATURE SYNTIIESISOF DIAMOND WITII NON-METALLICCATALYST H.Sumiya, S.Satoh. (Sumitomo Electric Ind., Hyogo, Japan.) Int. J. Refract. MetalslHard Mater., Vol 17, No 5, 1999, 345-350. It is noted that oxides of Fe with Ti, Si or Y are effective catalysts for synthesis of diamond at high pressures and temperatures and also enhance sintering in production of polycrystalline diamond. It is reported that polycrystalline diamond could be sintered at 1850 “C to high hardness and good heat resistance.
DEPENDENCE OF HARDNESS ON TEMPERATURE AND POROSITY OF SILICON CARBIDE CERAMICS Y.V.Milman et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Int. J. Refract. MetalslHard Mater., Vol 17, No 5,1999,361-368. The effects of temperature, 20 to 900 “C, and porosity, 0,5,16 or 20%, on Vickers microhardness of Sic ceramics were investigated. Athermal regions of hardness were detected at low temperatures, which are attributed to fracturing and not to plastic deformation, which occurs at higher temperatures. A relationship between hardness and porosity is given. Increase in porosity reduced fracture toughness. Temperature dependence of hardness, where there is high Peierls-Nabarro stress, is expressed diagrammatically, hardness being determined by plastic deformation, brittle fracture and phase transformations. TESTING OF COATED CEMENTED CARBIDES WITH TOUGH SURFACE LAYER J.Spacil. (Pramet Tools s.r.o., Sumperk, Czech Republic.) Pokroky Pras. Metal, Vol37, No 2,1999,45-54. (In Czech.) Testing of cemented carbide cutting tools, with tough and hard coatings, is discussed. Tests were carried out on tools with consideration of wear resistance, toughness and thermal stability. Samples studied included functionally gradient substrates and a range of coatings. Comparison is made with conventional materials. The new materials are shown to perform well, in a wide range of conditions, except in heavy cutting and fine finish cutting.
Hot
isostatic
pressing
PHOTOCHEMICAL SYNTHESIS OF _ MOLYBDENUMCARBIDE FOR MOLYBDENUMAND CARBON POWDERS
COST EFFECTIVE HOT ISOSTATIC PRESSING
N.Shohoju et al. (INETI, Lisbon, Portugal.) Int. J. Refract. MetalslHard Mater., Vol17, No 5,1999,351-356. Polymorphism in stoichiometric and non-stoichiometric MO carbides is described. Up to 1190 “C! the stable phase is orthohrombic clMo,C, between 1190 “C and 1655 “C hexagonal PMo,C is stable. Above 1655 “C a non-stoichiometric MO-C phase exists, hexagonal up to 1960 “C and face centred cubic between 1960 and the melting point, 2580 “C. Heating MO and C in a solar furnace at 1600 “C! resulted in synthesis of non-stoichiometic hexagonal MoC,,,, in 30 minutes. It is suggested that there is a photochemical reaction.
J.Westerlund et al. (ABB Pressure Systems AB, Vasteras, Sweden.) ht. J. Powder Metall., Vol 25, No 3, 1999, 31-35. Development of HIP as a viable production process is discussed. Development of equipment for HIP is reviewed with consideration of efficient production and the need for uniform rapid cooling. Comparison is made of the production requirements of different materials. It is shown that advances in processes can improve efficiency even though the initial costs are high. It is predicted that advances in technology will lead to lower costs and higher throughput of parts.