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Coatings
PM LITERATURE REVIEW
Coatings MICROSTRUCTURAL INVESTIGATION OF HEAT TREATED MULTI·LAYER KALUMINA COATINGS
A..Larrson et al. (Chalmers University of Technology, Gtiteborg, Gtiteborg, Sweden.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6, 1998,369-376. An investigation of microstructural evolution in the transformation K to aAl2 0 3 is described. The object was to determine the effects of the K microstructure. The multilayer had eight AlP3 layers, 0.8 usi: thick, with separating films of TiC, on a cemented WC substrate. The transformation was induced by heat treatment at 1030°C for up to seven hours. During transformation voids coalesced at the Al20iTiC interface and cracks formed. There were faceted voids within the aAl 20 3 grains. Three modes of transformation are identified, columnar, lateral and mixed columnarllateral. The mode depended on the nucleation:growth ratio. NUCLEATION AND GROWTH OF DIA· MOND DEPOSITED FROM COMBUS· TION FLAME ON SILICON NITRIDE
R.T.Rozbicki, V.K.Sarin. (Boston University, Boston, USA.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6, 1998, 377-388. An investigation of the effects of substrate temperature on the deposition of diamond from combustion flames on to Si 3N4 is described. It is shown that the nucleation density was 10 5 nuclei.crrr-'. The activation energy for diamond nucleation was 134 to 168 kJ.moP and for diamond growth 39.4 and 34.8 kJ.moP for centre and edge of deposit particles. Thermodynamics is used to show that SiC cannot form. It is reported that the diamond coatings can be deposited without extensive substrate preparation. CORRELATION BETWEEN SURFACE ACOUSTIC WAVEVELOCITY AND PROPERTIES OF TITANIUM NITRIDE
J.D.Comins et al. (University of Witwatersrand, Johannesburg. South Africa.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6, 1998, 389-394. Surface Brillouin scattering was used to study acoustic excitation in TiN films of mild and high speed steel substrates. It is reported that, for thinner films, reduced elastic moduli are required to give good agreement
40 MPR December 1999
between theory and experiment. This is attributed to a TiO film at the coating/substate interface. Residual stresses and critical loads are correlated with surface acoustic wave velocity. NEW ADHESION MEASUREMENT TECHNIQUE FOR COATED CUTTING TOOL MATERIALS
R.H.Dauskardt et al. (Stanford University, Stanford, USA.) Int. J. Refractory Metals Hard Mtiter., Vol 16, No 4-6, 1998, 395-402. Adhesion of surface coatings to cutting tool materials is discussed with regard to performance in service and the need for a rapid and reproducible test for adhesive properties. Development of a sandwich double cantilever beam test, for measurement of coating adhesion, is reported. Optical and electron microscopy were used to show that it is possible to characterize the adhesion of coatings to cutting tool alloys. CONSOLIDATION AND BONDING TO STAINLESS STEEL OF STELLITE BY SPARK PLASMA SINTERING
S.Sugiyama et al. (Akita Prefectural Industrial Technology Centre, Akita, Japan.) Jpn. Soc. Powder Powder Metall., Vol 45, No 7, 1998. (In Japanese.) Use of spark plasma sintering to consolidate stellite powder and bond it to a stainless steel substrate was investigated. Sintered stellite coatings were obtained in 10 minutes at 1070°C under 50 MPa pressure after heating at 50°C.min- 1. Good mechanical properties are attributed to finely dispersed carbides. The stellite bonded to the steel with a narrow diffusion zone due to short time and low temperature used.
Electrical and magnetic materials
6.9%B-0.8%Al-0.6%Zr. Process details are described. The MIM material had 4% less particle alignment and a maximum energy product of 232 kJ.m- 3. Residual C from the binder had an adverse effect on properties. PRODUCTION OF NEODYMIUM·IRON· BORON ALLOYS BY MECHANICAL ALLOYING
T.Saito. (Chiba Inst. of Technology, Narashino, Japan.) Jpn. Soc. Powder Powder Metall., Vol 45, No 7, 1998, 692696. (In Japanese.) It is reported that elemental Nd-FeB powders had been mechanically alloyed in N, Ar and H. Milled powders and powders heat treated, at various temperatures, were characterized by xray diffraction, microscopy and magnetometry. Nand H were absorbed during milling. Powders milled in H lost H during annealing, had high coercivity with a structure containing Nd 2Fe14B crystallites. N was not desorbed, the powders contained Nd and Fe nitrides and had low coercivity. Powders milled in H were magnetically isotropic. THERMO·ELECTRIC PROPERTIES OF MECHANICALLY ALLOYED P·TYPE SILICON-GERMANIUM
M.Niino et al. (Tohoku University, Sendai, Japan.) Jpn. Soc. Powder Powder Metall., Vol 45, No 8, 1998, 733737. (In Japanese.) It is reported that Si-20at%Ge powder had been mechanically alloyed to a particle size of 20 to 30 nm. The alloy was for thermo-electric applications. B was added to promote optimum performance. Thermo-electric properties were measured on hot pressed material at 25 to 800°C. The grain size of the alloy was about 200 nm.
Powder production
PROPERTIES OF INJECTION MOULD· ED SINTERED ANISOTROPIC NEODYMIUM·(IRON, COBALT)·BORON MAGNET
INFLUENCE OF ATOMIZING GAS PRES· SURE ON PARTICLE SHAPE OF ALU· MINIUM AND MAGNESIUM POWDERS
W.Lee et al. (Korea Inst. of Science and Technology, Seoul, Korea.) Powder Metall., Vol 41, No 3, 1998, 185-188. It is reported that sintered anisotropic Nd-(Fe,Co)-B magnet materials had been made by metal injection moulding and a conventional PM method in order to compare structures and properties. The alloy was Fe-14.7%Nd-12.9%Co-
S.Ozbilen. (Gazi University, Ankara, Turkey.) Powder Technol., Vol 102, No 2, 1999, 109-119. Al and Mg powders were produced by confined nozzle gas atomization to determine the effect of gas pressure on particle morphology. Mg particle sizes were 13 to 24 Jlm and for Al powders, 10 to 21 ur«, depending on gas pressure
Coatings MICROSTRUCTURAL INVESTIGATION OF HEAT TREATED MULTI·LAYER KALUMINA COATINGS
A..Larrson et al. (Chalmers University of Technology, Gtiteborg, Gtiteborg, Sweden.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6, 1998,369-376. An investigation of microstructural evolution in the transformation K to aAl2 0 3 is described. The object was to determine the effects of the K microstructure. The multilayer had eight AlP3 layers, 0.8 usi: thick, with separating films of TiC, on a cemented WC substrate. The transformation was induced by heat treatment at 1030°C for up to seven hours. During transformation voids coalesced at the Al20iTiC interface and cracks formed. There were faceted voids within the aAl 20 3 grains. Three modes of transformation are identified, columnar, lateral and mixed columnarllateral. The mode depended on the nucleation:growth ratio. NUCLEATION AND GROWTH OF DIA· MOND DEPOSITED FROM COMBUS· TION FLAME ON SILICON NITRIDE
R.T.Rozbicki, V.K.Sarin. (Boston University, Boston, USA.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6, 1998, 377-388. An investigation of the effects of substrate temperature on the deposition of diamond from combustion flames on to Si 3N4 is described. It is shown that the nucleation density was 10 5 nuclei.crrr-'. The activation energy for diamond nucleation was 134 to 168 kJ.moP and for diamond growth 39.4 and 34.8 kJ.moP for centre and edge of deposit particles. Thermodynamics is used to show that SiC cannot form. It is reported that the diamond coatings can be deposited without extensive substrate preparation. CORRELATION BETWEEN SURFACE ACOUSTIC WAVEVELOCITY AND PROPERTIES OF TITANIUM NITRIDE
J.D.Comins et al. (University of Witwatersrand, Johannesburg. South Africa.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6, 1998, 389-394. Surface Brillouin scattering was used to study acoustic excitation in TiN films of mild and high speed steel substrates. It is reported that, for thinner films, reduced elastic moduli are required to give good agreement
40 MPR December 1999
between theory and experiment. This is attributed to a TiO film at the coating/substate interface. Residual stresses and critical loads are correlated with surface acoustic wave velocity. NEW ADHESION MEASUREMENT TECHNIQUE FOR COATED CUTTING TOOL MATERIALS
R.H.Dauskardt et al. (Stanford University, Stanford, USA.) Int. J. Refractory Metals Hard Mtiter., Vol 16, No 4-6, 1998, 395-402. Adhesion of surface coatings to cutting tool materials is discussed with regard to performance in service and the need for a rapid and reproducible test for adhesive properties. Development of a sandwich double cantilever beam test, for measurement of coating adhesion, is reported. Optical and electron microscopy were used to show that it is possible to characterize the adhesion of coatings to cutting tool alloys. CONSOLIDATION AND BONDING TO STAINLESS STEEL OF STELLITE BY SPARK PLASMA SINTERING
S.Sugiyama et al. (Akita Prefectural Industrial Technology Centre, Akita, Japan.) Jpn. Soc. Powder Powder Metall., Vol 45, No 7, 1998. (In Japanese.) Use of spark plasma sintering to consolidate stellite powder and bond it to a stainless steel substrate was investigated. Sintered stellite coatings were obtained in 10 minutes at 1070°C under 50 MPa pressure after heating at 50°C.min- 1. Good mechanical properties are attributed to finely dispersed carbides. The stellite bonded to the steel with a narrow diffusion zone due to short time and low temperature used.
Electrical and magnetic materials
6.9%B-0.8%Al-0.6%Zr. Process details are described. The MIM material had 4% less particle alignment and a maximum energy product of 232 kJ.m- 3. Residual C from the binder had an adverse effect on properties. PRODUCTION OF NEODYMIUM·IRON· BORON ALLOYS BY MECHANICAL ALLOYING
T.Saito. (Chiba Inst. of Technology, Narashino, Japan.) Jpn. Soc. Powder Powder Metall., Vol 45, No 7, 1998, 692696. (In Japanese.) It is reported that elemental Nd-FeB powders had been mechanically alloyed in N, Ar and H. Milled powders and powders heat treated, at various temperatures, were characterized by xray diffraction, microscopy and magnetometry. Nand H were absorbed during milling. Powders milled in H lost H during annealing, had high coercivity with a structure containing Nd 2Fe14B crystallites. N was not desorbed, the powders contained Nd and Fe nitrides and had low coercivity. Powders milled in H were magnetically isotropic. THERMO·ELECTRIC PROPERTIES OF MECHANICALLY ALLOYED P·TYPE SILICON-GERMANIUM
M.Niino et al. (Tohoku University, Sendai, Japan.) Jpn. Soc. Powder Powder Metall., Vol 45, No 8, 1998, 733737. (In Japanese.) It is reported that Si-20at%Ge powder had been mechanically alloyed to a particle size of 20 to 30 nm. The alloy was for thermo-electric applications. B was added to promote optimum performance. Thermo-electric properties were measured on hot pressed material at 25 to 800°C. The grain size of the alloy was about 200 nm.
Powder production
PROPERTIES OF INJECTION MOULD· ED SINTERED ANISOTROPIC NEODYMIUM·(IRON, COBALT)·BORON MAGNET
INFLUENCE OF ATOMIZING GAS PRES· SURE ON PARTICLE SHAPE OF ALU· MINIUM AND MAGNESIUM POWDERS
W.Lee et al. (Korea Inst. of Science and Technology, Seoul, Korea.) Powder Metall., Vol 41, No 3, 1998, 185-188. It is reported that sintered anisotropic Nd-(Fe,Co)-B magnet materials had been made by metal injection moulding and a conventional PM method in order to compare structures and properties. The alloy was Fe-14.7%Nd-12.9%Co-
S.Ozbilen. (Gazi University, Ankara, Turkey.) Powder Technol., Vol 102, No 2, 1999, 109-119. Al and Mg powders were produced by confined nozzle gas atomization to determine the effect of gas pressure on particle morphology. Mg particle sizes were 13 to 24 Jlm and for Al powders, 10 to 21 ur«, depending on gas pressure