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Wear-resistant layers with stress relaxing interlayer in Cr treatment of cermets
discussed. It is reported that two-phase aFe/NdFeB material had been prepared by MA. The magnetic properties are described. The application was for exchange spring magnets. STRUCTUREAND MAGNETIC PROPERTIES OF MECHANICALLY DEFORMEDHEUSLERALLOYS F.Yin et al. (Konan University, Kobe, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol43, No 5, 1996, 669-674. (In English.) It is reported that mechanical milling of Heusler alloy powders resulted in synthesis of a nanocrystalline body centred cubic phase without ferromagnetism. This was stable up to 250°C and ferromagnetism was restored at about 140°C. Crystal structureswere described. clard
materialsanti tool
steels STRUCTUREOF MULTILAYERTiNA&O, COATINGS S.Vuorinen, M.Halversson. (Chalmers University of Technology, Goteborg, Sweden.) ht. J. Refractory Metals Hard Mater., Vol 15, No l/3, 1997, 169-178. Multilayered TiN and Al,O, coatings on cemented carbides were characterized for microstructure. A model for formation of domains in Also, is given. The height of columnar Also, twinned grains was of the same order as layer thickness and the preferred growth direction was along the c-axis. TiN deposited on Also, differed markedly from that deposited on cemented carbide. The layers were free from pores but there were numerous pores at interfaces. TiN deposited more rapidly on cemented carbide. Epitaxy was noted. Orientation relationships are described. Twins and stacking faults are discussed. WEAR-RESISTANTLAYERSWITH STRESS RELAXINGINTERLAYERIN Cr TREATMENTOF CERMETS I.Y.Konyashin. (Hard and Refractory Metals Research Inst., Moscow, Russia.) Znt. J. Refractory Metals Hard Mater., Vol 15, No l/3, 1997, 187-195. Surface layers produced by deposition of Cr on TiC and Ti(C,N) cermet substrates were investigated. The layers are shown to be an outer layer of (Cr,Ni),C, and a (Cr,Ni),,C, inner layer with a stress relaxing interlayer of CrNi solid solution between the carbide and the substrate. The interlayer is reported to arrest crack propagation from carbide to substrate. A three-fold increase in service life is reported.
STRUCTUREAND PROPERTIES OF TITANIUMBORIDETUNGSTEN CERMETSMADE BY HIP
SYNTHESISOF ALUMINIDESAT LOW TEMPERATUREBY MECHANICAL ALLOYING
A.Kawasaki et al. (Tohoku University, Sendai, Japan.) Mater. Trans. JIM, Vol 37, No 5, 1996, 1078-1083. Formation of a new phase during sintering of TiB,-W cermets and its effect on properties were investigated. TiB,-(5 to 4O)vol%W were densified by HIP at 1750°C and 200 MPa to 99%. The cermets contained TiB,, PWB and WTiB, with no residual W in compacts with less than 3O%W. Mechanical properties, including fracture toughness, increased with formation of WTiB, the amount of which increased with %W. Vicker’s hardness was above 20 GPa.
K.Kobayashi, K.Ozaki. Mater. Trans. JIM, Vol 37, No 4, 1996, 738-742. It is reported that mixed Ti-5wt%Al and Nb-lO%Al elemental powders had been processed by mechanical alloying. 4Ovol%Al was added to each, then hot pressed at 660°C and 20 MPa and heated to 925°C to synthesize the aluminides. Reaction temperature between the MA powder and the Al depended on milling time. 85% density was attained. Addition of ceramic particles reduced the required process temperature.
STRUCTUREAND PROPERTIESOF HOTWORK TOOL STEEL MATRIX COMPOSITESMADE BY HIP E.Pagounis et al. (Helsinki University of Technology, Espoo, Finland.) Powder Metal, Vol40, No 1, 1997, 55-61. Steel matrix composites for wearresistant applications are discussed. An investigation of a hot work tool steel, reinforced with ceramic particles, is described. HIP at 1100°C and 100 MPa for 3 hours was used for fabrication and gave near full density and good metal to ceramic bonding. Ceramic particles gave grain refinement and improved wear properties.
Intermetalk materials STRENGTHPROPERTIES OF IRON ALUMINIDES K.Yoshimi, S.Hanada. J. Metals, Vo144, No 8, 1997, 46-49. Development of Fe aluminides for structural use is reviewed with regard to slip and deformation. It is noted that properties of Fe aluminides are influenced by excess vacancy strengthening and a positive effect of temperature on yield stress. Control of these is regarded as essential. Strength properties of Fe aluminides are discussed.
CERAMICMOULD HIP PROCESSING OF NIOBIUMALUMINIDE H.Endo et al. (Daido Steel, Japan.) Mater. Trans. JIM, Vol 37, No 4, 1996, 828-834. The preparation of Nb&l by HIP of powder enclosed in a ceramic mould is reported. The ceramic moulds were made by a lost wax method and were enclosed in a steel can. The ceramics were Y,O, or Y,O,-CaO and acted as a pseudo-HIP pressure transfer medium. Various shapes were made. After HIP properties were low but were improved by heat treatment to remove prior particle boundaries. IN STRUCTUREAND PROPERTIESDURING SOLID SINTERINGOF Ni-Al POWDERS CHANGE
Y.Ito et al. (University of Hokkaido, Hokkaido, Japan.) Mater. Trans. JIM, Vol 37, No 4, 1996, 1067-1972. Low-temperature reactive sintering of elemental Ni-Al powders was investigated with reference to effects of process conditions on ambient temperature properties. Aluminide crystals and pores formed and grew during sintering. Thermodynamic properties are given. Pressure applied during processing enhanced densification.
Mechanical alloying
MECHANICALPROPERTIES, STRUCTUREAND FRACTUREOF NICKELALUMINIDE
INFLUENCEOF STRESS IN ATTRITIONMILL ON MECHANICAL ALLOYINGOF TITANIUM-ALUMINIUM
E.Bobrova et al. (Ustav Materialoveho Vyskumu SAV, Kosice, Czech Republic.) Pokroky Praskove Metal., Vol 34, No 3, 1996, 17-25. (In Czech.) Structure, mechanical properties and fracture of N&Al were investigated. Elemental powders were mixed and HIPed at 1200°C and 150 MPa for 1 hour. The object was to establish a relationshipbetween structureand properties.
K.Husemann. R.Rasper, (TU Bergakademie Freiberg, Freiberg, Germany.) Metall., Vol 51, No1/2, 1997, 44-50. (In German.) An investigation of MA of Ti-Al powder in an attrition mill is described. The effects of stressing conditions and energy absorption by the powder were determined. Milling atmosphere and contamination are considered. X-ray diffraction
MPR February1999 39
materialsanti tool
steels STRUCTUREOF MULTILAYERTiNA&O, COATINGS S.Vuorinen, M.Halversson. (Chalmers University of Technology, Goteborg, Sweden.) ht. J. Refractory Metals Hard Mater., Vol 15, No l/3, 1997, 169-178. Multilayered TiN and Al,O, coatings on cemented carbides were characterized for microstructure. A model for formation of domains in Also, is given. The height of columnar Also, twinned grains was of the same order as layer thickness and the preferred growth direction was along the c-axis. TiN deposited on Also, differed markedly from that deposited on cemented carbide. The layers were free from pores but there were numerous pores at interfaces. TiN deposited more rapidly on cemented carbide. Epitaxy was noted. Orientation relationships are described. Twins and stacking faults are discussed. WEAR-RESISTANTLAYERSWITH STRESS RELAXINGINTERLAYERIN Cr TREATMENTOF CERMETS I.Y.Konyashin. (Hard and Refractory Metals Research Inst., Moscow, Russia.) Znt. J. Refractory Metals Hard Mater., Vol 15, No l/3, 1997, 187-195. Surface layers produced by deposition of Cr on TiC and Ti(C,N) cermet substrates were investigated. The layers are shown to be an outer layer of (Cr,Ni),C, and a (Cr,Ni),,C, inner layer with a stress relaxing interlayer of CrNi solid solution between the carbide and the substrate. The interlayer is reported to arrest crack propagation from carbide to substrate. A three-fold increase in service life is reported.
STRUCTUREAND PROPERTIES OF TITANIUMBORIDETUNGSTEN CERMETSMADE BY HIP
SYNTHESISOF ALUMINIDESAT LOW TEMPERATUREBY MECHANICAL ALLOYING
A.Kawasaki et al. (Tohoku University, Sendai, Japan.) Mater. Trans. JIM, Vol 37, No 5, 1996, 1078-1083. Formation of a new phase during sintering of TiB,-W cermets and its effect on properties were investigated. TiB,-(5 to 4O)vol%W were densified by HIP at 1750°C and 200 MPa to 99%. The cermets contained TiB,, PWB and WTiB, with no residual W in compacts with less than 3O%W. Mechanical properties, including fracture toughness, increased with formation of WTiB, the amount of which increased with %W. Vicker’s hardness was above 20 GPa.
K.Kobayashi, K.Ozaki. Mater. Trans. JIM, Vol 37, No 4, 1996, 738-742. It is reported that mixed Ti-5wt%Al and Nb-lO%Al elemental powders had been processed by mechanical alloying. 4Ovol%Al was added to each, then hot pressed at 660°C and 20 MPa and heated to 925°C to synthesize the aluminides. Reaction temperature between the MA powder and the Al depended on milling time. 85% density was attained. Addition of ceramic particles reduced the required process temperature.
STRUCTUREAND PROPERTIESOF HOTWORK TOOL STEEL MATRIX COMPOSITESMADE BY HIP E.Pagounis et al. (Helsinki University of Technology, Espoo, Finland.) Powder Metal, Vol40, No 1, 1997, 55-61. Steel matrix composites for wearresistant applications are discussed. An investigation of a hot work tool steel, reinforced with ceramic particles, is described. HIP at 1100°C and 100 MPa for 3 hours was used for fabrication and gave near full density and good metal to ceramic bonding. Ceramic particles gave grain refinement and improved wear properties.
Intermetalk materials STRENGTHPROPERTIES OF IRON ALUMINIDES K.Yoshimi, S.Hanada. J. Metals, Vo144, No 8, 1997, 46-49. Development of Fe aluminides for structural use is reviewed with regard to slip and deformation. It is noted that properties of Fe aluminides are influenced by excess vacancy strengthening and a positive effect of temperature on yield stress. Control of these is regarded as essential. Strength properties of Fe aluminides are discussed.
CERAMICMOULD HIP PROCESSING OF NIOBIUMALUMINIDE H.Endo et al. (Daido Steel, Japan.) Mater. Trans. JIM, Vol 37, No 4, 1996, 828-834. The preparation of Nb&l by HIP of powder enclosed in a ceramic mould is reported. The ceramic moulds were made by a lost wax method and were enclosed in a steel can. The ceramics were Y,O, or Y,O,-CaO and acted as a pseudo-HIP pressure transfer medium. Various shapes were made. After HIP properties were low but were improved by heat treatment to remove prior particle boundaries. IN STRUCTUREAND PROPERTIESDURING SOLID SINTERINGOF Ni-Al POWDERS CHANGE
Y.Ito et al. (University of Hokkaido, Hokkaido, Japan.) Mater. Trans. JIM, Vol 37, No 4, 1996, 1067-1972. Low-temperature reactive sintering of elemental Ni-Al powders was investigated with reference to effects of process conditions on ambient temperature properties. Aluminide crystals and pores formed and grew during sintering. Thermodynamic properties are given. Pressure applied during processing enhanced densification.
Mechanical alloying
MECHANICALPROPERTIES, STRUCTUREAND FRACTUREOF NICKELALUMINIDE
INFLUENCEOF STRESS IN ATTRITIONMILL ON MECHANICAL ALLOYINGOF TITANIUM-ALUMINIUM
E.Bobrova et al. (Ustav Materialoveho Vyskumu SAV, Kosice, Czech Republic.) Pokroky Praskove Metal., Vol 34, No 3, 1996, 17-25. (In Czech.) Structure, mechanical properties and fracture of N&Al were investigated. Elemental powders were mixed and HIPed at 1200°C and 150 MPa for 1 hour. The object was to establish a relationshipbetween structureand properties.
K.Husemann. R.Rasper, (TU Bergakademie Freiberg, Freiberg, Germany.) Metall., Vol 51, No1/2, 1997, 44-50. (In German.) An investigation of MA of Ti-Al powder in an attrition mill is described. The effects of stressing conditions and energy absorption by the powder were determined. Milling atmosphere and contamination are considered. X-ray diffraction
MPR February1999 39