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Potential of high speed steels in anti-fretting applications
properties of resin bonded magnets were reduced cost. Heat improved at treatment of the powder was optimized at 725 to 825°C for a few minutes. Low Co and high Co alloys had coercive forces of 600 and 1000 Oe, respectively. STRUCTURAL AND MAGNETIC CHARACTERIZATION OF BARIIJMSTRONTIUM HEXAFERRITE POWDERS F.Ruiz et al. (Autonomous University of San Luis Potosi, San Luis Potosi, Mexico.) Reu. Metall. Madrid, Vol 35, No 3,1999,143-147. Magnetic and structural characteristics of ferromagnetic powder materials, based on Ba-Sr-Fe-O, were investigated by atomic force microscopy, X-ray diffraction and magnetometry. Samples were presintered at 800 and 1000°C and sintered at 1200°C for 1 hour. Inter-sample differences were detected. Structure-magnetic property relationships are discussed. SYNTHESIS OF THERMO-ELECTRIC MATERIALS BY MECHANICAL ALLOYING IN PLANETARY BALL MILLS J.Schilz et al. (Inst. fur WerkstoffeForschung, Cologne, Germany.) Powder Technol., Vol 105, No 1-3, 1999, 149-154. Effects of milling conditions on alloy Si-Ge, Mg,Si and synthesis in Mg,(Si,Sn) thermoelectric materials were investigated. It is shown that mill geometry and ratios of angular velocities are crucial in determining mill performance. In Si-Ge, alloying was shown to be by a solid state diffusion mechanism. With Mg,Si and Mg,(Si,Sn), alloying proceeds at the surfaces of the Mg particles. A transient Mg,Sn phase was detected. MECHANICAL ALLOYING OF LITHIUM-MANGANESE SPINEL FOR LITHIUM SECONDARY BATTERIES K.Hasezaki, M.Kamada. (Mitsubishi Heavy Industries Ltd, Yokohama, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 3,1999,317-320. (In Japanese.) It is reported that mechanical alloying of powder raw materials, for 200 hours, in Ar, and annealing at 550°C for 3 hours, had been used to synthesize a Li-Mn spinel, LiMnzOb, for use in Li secondary batteries. Powders were about 0.1 pm in size. Performance of the materials was evaluated in a 4V Li cell with a non-aqueous electrolyte.
Hard materials steels
and tool
POTENTIAL OF HIGH SPEED STEELS IN ANTI-FRETTING APPLICATIONS
et al. (University of A.S.Wronski Bradford, Bradford, UK.) Powder Metall., Vol42, No 1, 1999,63-69. Use of high speed steels in wear resistant applications are reviewed. It is noted that wear resistance is increased by additions of hard particles to the steel, in addition to the natural MC and M,C! carbides, and that friction can be reduced by solid lubricants. Difficulty in correlating service performance with wear tests, such as pin-on-disc, and tests for fretting, are considered. A new test for fretting is introduced. Results of tests are presented. Materials response fretting maps are interpreted in the light of damage to materials and microstructures. MECHANICAL BEHAVIOUR OF HARDMETALS FOR CUTTING TOOLS D.Mari et al. (Ecole Polytechnique Federale, Lausanne, Switzerland.) Znt. J. Refract. Metals Hard Mater., Vol 17, No l/3, 1999, 209-225. WC-(Ni or Co) and (Ti, Mo)C-(Ni or are discussed. hardmetals Co) inmechanical Structural and vestigations are described. Structures are regarded as two interpenetrating skeletons, one of metal binder phase, which can be leached chemically, and the other of the hard phase. The properties of the hard phase skeleton alone and the whole cermet are compared by bend tests at a range of compositions and temperatures. Brittle, plastic and limited plasticity regimes are identified and transitions are described. High temperature deformation was studied. It is shown that temperature jumps lead to a more stable than tests. microstructure creep Mechanical spectroscopy was used to determine defect dynamics responsible for deformation. Results were supported by electron microscopy. ACCELERATED INVESTIGATION OF CARBOTHERMAL REACTIONS K.Wetzig et al. (Inst. of Solid State and Materials Research, Dresden, Germany.) Int. J. Refract. Metals Hard Mater., Vol 17, No l/3, 1999,227-234. Kinetics of carbothermal processes for reduction of metal oxides, in production of hard materials, were investigated with regard to starting materials, fine grained ZrO, and TiO, and various forms of C under different conditions. Measurements process were made over 1000 to 2000°C and under isothermal conditions in this products were range. Solid characterized. The studies are said to be of value in development of process improvements.
EFFECTS OF CARBON CONTENT ON STRUCTURE AND PROPERTIES OF CARBO-NITRIDE CERMETS J.Zackrisson, H.O.Andren. (Chalmers University of Technology, Goteborg, Sweden.) Int. J. Refract. Metals Hard Mater., Vol 17, No 4, 1999, 265-273. Five alloys, based on (W, Ti, Ta, Mo)(C, N)-(Co, Nil, with different %C were investigated to relate %C with structure and properties. As %C increased the %W and %Ti in the binder diminished, there was a lower volume fraction of undissolved Ti(C, Nl cores and a higher proportion of (Ti, W, Ta)(C, N) cores. Amounts of other phases and their compositions were little affected by %C. Hardness decreased and transverse with increased rupture strength increased %C. %C had little influence on wear resistance, which was high due to solid solution hardening of the binder. EFFECT OF POROSITY ON GRINDING PERFORMANCE OF CAST IRON BONDED DIAMOND CUTTING WHEEL RIshizaki et al. (Nagaoka University of Technology, Nagaoka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 3, 1999, 257-261. (In English.) It is reported that a porous cast iron bonded diamond cutting material has been developed and is shown to perform well with structural ceramics. Effects of a range of porosity were investigated on materials made by a pulsed electric current sintering technique. It is shown that wear rate increased with increase in porosity, grinding energy was low with porosity over 25% and there was an optimum porosity which gave the maximum grinding rate. LIQUID PHASE SINTERING OF HIGH SPEED STEELS A.S.Wronski et al. (University of Bradford, Bradford, UK.) Powder Metall., Vo142, No 2, 1999, 131-146. Calculated phase diagrams were used to identify six high speed steel sinwith enhanced compositions terability. Alloys were prepared from atomized and other powders by pressing to a green density of 70% and vacuum sintering. Some alloys sintered to full density at 1150°C 70 to 150°C lower than existing alloys, with a sintering window of 20 to 30°C. Sinterability was discussed in terms of sintered density and microstructure. Structures, heat cutting response and treatment performance are evaluated and are shown to be superior to M2 and Tl steels of identical geometry. %C was shown to be critical. Too low a %C increased sintering temperature and reduced the sintering window. Too much C reduced sinterability due to M,C
MPR July/August
2000
27
Hard materials steels
and tool
POTENTIAL OF HIGH SPEED STEELS IN ANTI-FRETTING APPLICATIONS
et al. (University of A.S.Wronski Bradford, Bradford, UK.) Powder Metall., Vol42, No 1, 1999,63-69. Use of high speed steels in wear resistant applications are reviewed. It is noted that wear resistance is increased by additions of hard particles to the steel, in addition to the natural MC and M,C! carbides, and that friction can be reduced by solid lubricants. Difficulty in correlating service performance with wear tests, such as pin-on-disc, and tests for fretting, are considered. A new test for fretting is introduced. Results of tests are presented. Materials response fretting maps are interpreted in the light of damage to materials and microstructures. MECHANICAL BEHAVIOUR OF HARDMETALS FOR CUTTING TOOLS D.Mari et al. (Ecole Polytechnique Federale, Lausanne, Switzerland.) Znt. J. Refract. Metals Hard Mater., Vol 17, No l/3, 1999, 209-225. WC-(Ni or Co) and (Ti, Mo)C-(Ni or are discussed. hardmetals Co) inmechanical Structural and vestigations are described. Structures are regarded as two interpenetrating skeletons, one of metal binder phase, which can be leached chemically, and the other of the hard phase. The properties of the hard phase skeleton alone and the whole cermet are compared by bend tests at a range of compositions and temperatures. Brittle, plastic and limited plasticity regimes are identified and transitions are described. High temperature deformation was studied. It is shown that temperature jumps lead to a more stable than tests. microstructure creep Mechanical spectroscopy was used to determine defect dynamics responsible for deformation. Results were supported by electron microscopy. ACCELERATED INVESTIGATION OF CARBOTHERMAL REACTIONS K.Wetzig et al. (Inst. of Solid State and Materials Research, Dresden, Germany.) Int. J. Refract. Metals Hard Mater., Vol 17, No l/3, 1999,227-234. Kinetics of carbothermal processes for reduction of metal oxides, in production of hard materials, were investigated with regard to starting materials, fine grained ZrO, and TiO, and various forms of C under different conditions. Measurements process were made over 1000 to 2000°C and under isothermal conditions in this products were range. Solid characterized. The studies are said to be of value in development of process improvements.
EFFECTS OF CARBON CONTENT ON STRUCTURE AND PROPERTIES OF CARBO-NITRIDE CERMETS J.Zackrisson, H.O.Andren. (Chalmers University of Technology, Goteborg, Sweden.) Int. J. Refract. Metals Hard Mater., Vol 17, No 4, 1999, 265-273. Five alloys, based on (W, Ti, Ta, Mo)(C, N)-(Co, Nil, with different %C were investigated to relate %C with structure and properties. As %C increased the %W and %Ti in the binder diminished, there was a lower volume fraction of undissolved Ti(C, Nl cores and a higher proportion of (Ti, W, Ta)(C, N) cores. Amounts of other phases and their compositions were little affected by %C. Hardness decreased and transverse with increased rupture strength increased %C. %C had little influence on wear resistance, which was high due to solid solution hardening of the binder. EFFECT OF POROSITY ON GRINDING PERFORMANCE OF CAST IRON BONDED DIAMOND CUTTING WHEEL RIshizaki et al. (Nagaoka University of Technology, Nagaoka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 3, 1999, 257-261. (In English.) It is reported that a porous cast iron bonded diamond cutting material has been developed and is shown to perform well with structural ceramics. Effects of a range of porosity were investigated on materials made by a pulsed electric current sintering technique. It is shown that wear rate increased with increase in porosity, grinding energy was low with porosity over 25% and there was an optimum porosity which gave the maximum grinding rate. LIQUID PHASE SINTERING OF HIGH SPEED STEELS A.S.Wronski et al. (University of Bradford, Bradford, UK.) Powder Metall., Vo142, No 2, 1999, 131-146. Calculated phase diagrams were used to identify six high speed steel sinwith enhanced compositions terability. Alloys were prepared from atomized and other powders by pressing to a green density of 70% and vacuum sintering. Some alloys sintered to full density at 1150°C 70 to 150°C lower than existing alloys, with a sintering window of 20 to 30°C. Sinterability was discussed in terms of sintered density and microstructure. Structures, heat cutting response and treatment performance are evaluated and are shown to be superior to M2 and Tl steels of identical geometry. %C was shown to be critical. Too low a %C increased sintering temperature and reduced the sintering window. Too much C reduced sinterability due to M,C
MPR July/August
2000
27