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Wear and corrosion resistance of PM tool steels
Cu-SOwt%Ni alloy parts were produced, by injection moulding from elemental Cu-Ni and from prealloyed CuNi powder. When sintered in N parts made from elemental powders had the higher density, but when vacuum sintered parts made from prealloyed powder had higher density. 0 and C contents and mechanical properties are described. PM2TEC’98. The following Abstracts are of papers that were presented at the 1998 International Conference on Powder Metallurgy and Particulate Materials held in Las Vegas, NV, USA, in June 1998.
Alloying element addition EFFECT OF SILICON ON OXIDATION OF SINTERED HOT FORGED COPPER-ALUMINIUM P.Aravindan, K.S.Pandey. (Regional Engineering College, Tiruchipalli, India.) Oxidation of sintered and hot forged Cu-6.7%Al-(0, 1 or 2)%Si was quantitatively investigated at 250,350 and 450°C. Thermodynamic functions and rate constants were determined. It is shown that the alloy with 2%Si can be heated in air because of protective oxide layers.
lntermetallic materials POWDER PROCESSING OF IRON ALUMINIDES S.C.Deevi. (Philip Morris Inc, USA.) Fe aluminides were discussed with reference to properties, high melting point, low density and oxidation resistance. It was reported that PM techniques, hot pressing and hot extrusion, had been used to prepare Fe aluminides, with 20 to 30%Al, and Fe aluminide composites reinforced with ceramic particles. Mechanical properties were measured and higher tensile strengths were obtained than with equivalent cast alloys. Fracture surfaces showed evidence of ductile tearing and brittle fracture in the cast materials. Effects of process conditions on structure and properties were discussed. PROCESSING AND CI-IARACTERIZATION OF MECIL4NICALLY ALLOYED NICKEL ALUMINIDE COMPOSITES P.Nash et al. (Illinois Inst. of Technology, USA.) It was reported that NiAl, with AlN dispersoids, mechanical
had been prepared by alloying in a reactive
38 MPR January 1999
pressing. and hot atmosphere Composites were also made by blending MA powders with Also, fibres and hot pressing. Creep properties were examined. The materials with AlN only had higher elevated temperature compressive strength and lower creep rates than the aluminide with fibre reinforcements. PROTECTION OF TITANIUMALUMINIUM FROM IRON CONTAMINATION DURING MECHANICAL ALLOYING H.Huang, T.Tianen. (Tampere University of Technology, Finland.) Contamination of powders by residues from milling tools was discussed. In particular, Fe in Ti-Al powder was investigated with regard to the use of a protective coating on the milling tools, milling times and the time to failure of the coating. It was shown that a protective coating could be formed by milling a small amount of Ti-Al powder, for 2 hours, with a process control agent. This protected Ti-Al powders from contamination during subsequent milling. REACTIVE BALL MILLING OF TITANIUM-ALUMINUM POWDER IN HYDROGEN K.S.Lee, K.I.Moon. (Hanyang University, Korea.) Reactive ball milling of elemental Ti-Al powders, in H, was investigated. TiH, was formed in l-3 hours. TiH, is shown to be essential in refining grain and particle sizes which were refined by increases in %Ti and milling times. Particle sizes were of nanometre dimensions and the powder was a dispersion of TiH, in an Al matrix. Grain size was relined first and then particle size.
Wear resistance
LUBRICANTS FOR SINTERED METAL PLAIN BEARINGS H.Miller. (Kluber Lubrication AG, Munchen, Germany.) Performance and failure of PM lubricant filled bearing materials were discussed in relation to design of bearing and shaft. Strategies to extend service life of sintered plain bearings were presented. TRIBOLOGICAL BEBAVIOUR AND MICROSTRUCTURE OF SINTERED ZINC-ALUMINIUM ALLOYS L.Wen et al. (South China University of Technology, China.) Zn-27wt%Al alloys, modified by addition of Mn, Ti, Ni, B and rare earths, were prepared from N atomized powders by compaction and sintering at 400°C. Lubricated and un-lubricated wear of the PM materials was compared with cast Zn-27%Al alloys and sintered bronze. Wear resistance and anti-friction properties of the PM alloy were shown to be superior to those of the cast alloy and the bronze. Optical and electron microscopy were used to investigate structures and wear surfaces.
Sinter hardening WHAT IS SINTER HARDENING? B.James. (Hoeganaes Corp, USA.) Sinter hardening was discussed with reference to its use to omit a heat treatment finishing stage to produce a martensitic structure in a part. The distinction between hardness and hardenability was described. It was noted that some steels are martensitic after sintering but others may require accelerated cooling to form martensite. This factor can be incorporated in furnace design and process operation to make sinterhardened parts.
OF PM TOOL STEELS
MATHEMATICAL EQUATION FOR PREDICTION OF SINTER HARDENABILITY
M.O.Speidel et al. (ETH, Zurich, Switzerland.) Wear resistance of PM tool steels was discussed and shown to depend on hardness and on composition, size and volume fraction of dispersed carbides, nitrides and carbo-nitrides. Corrosion resistance was shown to depend on concentration of alloy elements, Cr, MO and N, in the matrix. Two martensitic PM tools steels, with large concentrations of dispersoids and N, were made by hot pressing nitrided powder mixed with VC or TIN. Wear and corrosion resistance were described and compared with those of other PM steels and commercially available tool steels.
A.de Rege et al. (Domfer Metal Powders Ltd, Canada.) The need for a database for hardenability of sintered steels, incorporating materials and process parameters, was discussed. In particular cooling rate and density were considered. Relationships between hardness, cooling rate, microstructure and density were investigated. The results were analysed to yield a mathematical equation relating hardness, cooling rate and density for a steel. The expression was shown to permit prediction of the cooling rate required to attain a specified hardness and the effect of density on the hardness of the part.
WEAR fiNDCORROSION RESISTANCE
Alloying element addition EFFECT OF SILICON ON OXIDATION OF SINTERED HOT FORGED COPPER-ALUMINIUM P.Aravindan, K.S.Pandey. (Regional Engineering College, Tiruchipalli, India.) Oxidation of sintered and hot forged Cu-6.7%Al-(0, 1 or 2)%Si was quantitatively investigated at 250,350 and 450°C. Thermodynamic functions and rate constants were determined. It is shown that the alloy with 2%Si can be heated in air because of protective oxide layers.
lntermetallic materials POWDER PROCESSING OF IRON ALUMINIDES S.C.Deevi. (Philip Morris Inc, USA.) Fe aluminides were discussed with reference to properties, high melting point, low density and oxidation resistance. It was reported that PM techniques, hot pressing and hot extrusion, had been used to prepare Fe aluminides, with 20 to 30%Al, and Fe aluminide composites reinforced with ceramic particles. Mechanical properties were measured and higher tensile strengths were obtained than with equivalent cast alloys. Fracture surfaces showed evidence of ductile tearing and brittle fracture in the cast materials. Effects of process conditions on structure and properties were discussed. PROCESSING AND CI-IARACTERIZATION OF MECIL4NICALLY ALLOYED NICKEL ALUMINIDE COMPOSITES P.Nash et al. (Illinois Inst. of Technology, USA.) It was reported that NiAl, with AlN dispersoids, mechanical
had been prepared by alloying in a reactive
38 MPR January 1999
pressing. and hot atmosphere Composites were also made by blending MA powders with Also, fibres and hot pressing. Creep properties were examined. The materials with AlN only had higher elevated temperature compressive strength and lower creep rates than the aluminide with fibre reinforcements. PROTECTION OF TITANIUMALUMINIUM FROM IRON CONTAMINATION DURING MECHANICAL ALLOYING H.Huang, T.Tianen. (Tampere University of Technology, Finland.) Contamination of powders by residues from milling tools was discussed. In particular, Fe in Ti-Al powder was investigated with regard to the use of a protective coating on the milling tools, milling times and the time to failure of the coating. It was shown that a protective coating could be formed by milling a small amount of Ti-Al powder, for 2 hours, with a process control agent. This protected Ti-Al powders from contamination during subsequent milling. REACTIVE BALL MILLING OF TITANIUM-ALUMINUM POWDER IN HYDROGEN K.S.Lee, K.I.Moon. (Hanyang University, Korea.) Reactive ball milling of elemental Ti-Al powders, in H, was investigated. TiH, was formed in l-3 hours. TiH, is shown to be essential in refining grain and particle sizes which were refined by increases in %Ti and milling times. Particle sizes were of nanometre dimensions and the powder was a dispersion of TiH, in an Al matrix. Grain size was relined first and then particle size.
Wear resistance
LUBRICANTS FOR SINTERED METAL PLAIN BEARINGS H.Miller. (Kluber Lubrication AG, Munchen, Germany.) Performance and failure of PM lubricant filled bearing materials were discussed in relation to design of bearing and shaft. Strategies to extend service life of sintered plain bearings were presented. TRIBOLOGICAL BEBAVIOUR AND MICROSTRUCTURE OF SINTERED ZINC-ALUMINIUM ALLOYS L.Wen et al. (South China University of Technology, China.) Zn-27wt%Al alloys, modified by addition of Mn, Ti, Ni, B and rare earths, were prepared from N atomized powders by compaction and sintering at 400°C. Lubricated and un-lubricated wear of the PM materials was compared with cast Zn-27%Al alloys and sintered bronze. Wear resistance and anti-friction properties of the PM alloy were shown to be superior to those of the cast alloy and the bronze. Optical and electron microscopy were used to investigate structures and wear surfaces.
Sinter hardening WHAT IS SINTER HARDENING? B.James. (Hoeganaes Corp, USA.) Sinter hardening was discussed with reference to its use to omit a heat treatment finishing stage to produce a martensitic structure in a part. The distinction between hardness and hardenability was described. It was noted that some steels are martensitic after sintering but others may require accelerated cooling to form martensite. This factor can be incorporated in furnace design and process operation to make sinterhardened parts.
OF PM TOOL STEELS
MATHEMATICAL EQUATION FOR PREDICTION OF SINTER HARDENABILITY
M.O.Speidel et al. (ETH, Zurich, Switzerland.) Wear resistance of PM tool steels was discussed and shown to depend on hardness and on composition, size and volume fraction of dispersed carbides, nitrides and carbo-nitrides. Corrosion resistance was shown to depend on concentration of alloy elements, Cr, MO and N, in the matrix. Two martensitic PM tools steels, with large concentrations of dispersoids and N, were made by hot pressing nitrided powder mixed with VC or TIN. Wear and corrosion resistance were described and compared with those of other PM steels and commercially available tool steels.
A.de Rege et al. (Domfer Metal Powders Ltd, Canada.) The need for a database for hardenability of sintered steels, incorporating materials and process parameters, was discussed. In particular cooling rate and density were considered. Relationships between hardness, cooling rate, microstructure and density were investigated. The results were analysed to yield a mathematical equation relating hardness, cooling rate and density for a steel. The expression was shown to permit prediction of the cooling rate required to attain a specified hardness and the effect of density on the hardness of the part.
WEAR fiNDCORROSION RESISTANCE