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Lapping of PM materials
precipitation and contribution of solid state sintering are summarized and discussed. MICROWAVE SINTERING OF CERAMICS, CERMETS AND CEMENTED CARBIDES (University of M.Willert-Porada. Dortmund, Germany.) Microstructures and densities developed during microwave and conventional sintering of ceramics and cemented carbides are compared. Microwave sintering was shown to enhance densification and homogeneity, to reduce porosity and grain size and to give more rapid densification. The increased homogeneity was explained in terms of the microwave field affecting the driving force for densification and grain growth. Depth of penetration of the microwave field into the work was considered with respect to material and process parameters.
Post
sintering
THERMOCHEMICAL TREATMENT OF PM MATERL4LS WITH CARBON AND MTROGEN Vlancau et al. (Technical University of Cluj-Napoca, Cluj-Napoca, Romania.) Carburizing, nitriding and carbonitriding of sintered steel parts were investigated with respect to effects of part porosity and process conditions on surface structure and properties. Correlations were established between material and process parameters and characteristics of the thermo-chemically treated layers. PHASE COMPOSITION AND SURFACE HARDNESS OF ION-MTROCARBURIZED LAYER ON SINTERED STEEL H.Yin et al. (Research Inst. for Powder Metallurgy, Beijing, China. ) Sintered steel samples, un-alloyed and containing Cu, MO, Ni and Cr, were ion-nitrocarburized for a range of times, temperatures and gas chemistries. Effects of steel composition and process conditions on case depth and structure were determined. It was reported that case depth was increased by addition of C and MO and the amount of ycarbonitride was increased by increased concentration of Cu and Ni. The case depths were 10 to 25 pm and Vickers hardness was 500 to 800.
LAPPING OF PM MATERIALS A.Barylski. (Technical University of Gdansk, Gdansk , Poland.) A study of the rate of material removal in lapping PM materials was described. An artificial material was used as a standard and effects of pressure and size and type of abrasive, SIC and syn-
thetic corundum, were investigated. The SIC was reported to be better for hard materials and corundum for soft sintered materials. PROPERTIES OF INDUCTION HARDENED PM STEEL PARTS M.Rosso et al. (Polytechnic of Torino, Torino, Italy.) Induction hardening of steel parts was discussed and it was noted that closer control is required for sintered parts than for wrought steel. Induction hardening of sintered parts was investigated. The influence of alloy content was evaluated.
Testing measurement and control MICRO-COMPUTER TOMOGRAPHY FOR CHARACTERIZATION OF INNER VOLUME OF PM PARTS K.Pischang et al. (Dresden University of Technology, Dresden, Germany.) Defects, and their detection in PM parts, were discussed with reference to causes and difficulties in characterizing the inner volume. It was shown that the inner volume can be visualized by the use of micro-computer tomography. This allows measurement of density distribution. Examples were given. The technique was described and discussed. POROSITY DISTRIBUTION IN PM STEELS R.Norling. (Lund University, Lund, Sweden.) Porosity in PM steels was investigated by quantitative metallography on 16 sucessive polished sections, each 0.1 mm deeper into the specimen than the last. Porosities of 4 to 12% were found. The distribution of porosity differed for each steel. Fe-2%Cu-0.8% showed low porosity at corners and at the centre. Fe4%Ni-1.5%Cu-0.5%Mo-0.5%C had low porosity at edges and centre. ASSESSMENT OF GREEN COMPACTS BY 3-DIMENSIONAL TOMOGRAPHY T.Rabe et al. (Federal Inst. for Materials Research and Testing, Germany.) Occurrence of density gradients and cracks in green compacts was discussed, These may go undetected. It was shown that 3D X-ray tomography can be used to study density distribution in green parts. Examples of use of the technique were presented. DIRECT CURRENT POTENTIAL DROP METHOD FOR ASSESSMENT OF GREEN COMPACTS P.Luukkonen, T.Ericsson. University, Sweden.)
(Linkopings
The need for an on-line nondestructive test method for detection of cracks in green compacts was noted. It was shown that a Direct Current Potential Drop technique can be used. Development of the method to separate the crack signal from other factors was outlined and an optimum design of test probe was described. Use of the technique on a twolevel part, made by double action compaction with split punches was presented.
Intermetallic
materials
FABRICATION OF TITANIUM-NICKEL ALLOY BY SPARK PLASMA SINTERING H.Kyogoku et al. (Kinki University, Higashihiroshima, Japan.) Effects of process conditions on mechanical properties and shape memory characteristics of spark plasma sintered and heat treated TiNi, made from gas atomized Fe and carbonyl Ni powders, were investigated. 98.5%density was attained. Sintering, for 40 minutes at 95O”C, with the heat treatment gave a significantly homogeneous microstructure. The PM alloy exhibited shape memory characteristics but the mechanical properties were inferior to those of wrought alloys. SHAPE FORMING SPARK PLASMA SINTERING OF TITANIUM ALUMINIDE FOR AUTOMOBILE VALVE T.Abe et al. (Tohoku National Industrial Research Inst., Sendai, Japan.) TiAl powders were synthesized by mechanical alloying or by combustion synthesis of mixed powders, and consolidated by spark plasma sintering. Three point bend strengths were over 1 GPa for mechanically alloyed powder and 670 MPa for the combustion synthesized material. Sintered rods 5 cm long and 8 mm in diameter were produced and joined. The valve shape was made by further addition of TiAl powder and sinter joining to the rod. Near full density was reported.
Metal
matrix
composites
CHARACTERIZATION OF ALUMINIUM MATRIX COMPOSITES WITH INTERMETALLIC POWDER PARTICLES M.Lieblich, B.Torres-Barreiro. (Insamet, Spain.) It was reported that Al matrix composites, reinforced with particulate intermetallic compounds, in various proportions and particle sizes, had been prepared from elemental Al and intermetallic compound powders. Structures of consolidated materials were investigated as functions of material and process parameters. Mechanical properties and
MPR May 2000
49
Post
sintering
THERMOCHEMICAL TREATMENT OF PM MATERL4LS WITH CARBON AND MTROGEN Vlancau et al. (Technical University of Cluj-Napoca, Cluj-Napoca, Romania.) Carburizing, nitriding and carbonitriding of sintered steel parts were investigated with respect to effects of part porosity and process conditions on surface structure and properties. Correlations were established between material and process parameters and characteristics of the thermo-chemically treated layers. PHASE COMPOSITION AND SURFACE HARDNESS OF ION-MTROCARBURIZED LAYER ON SINTERED STEEL H.Yin et al. (Research Inst. for Powder Metallurgy, Beijing, China. ) Sintered steel samples, un-alloyed and containing Cu, MO, Ni and Cr, were ion-nitrocarburized for a range of times, temperatures and gas chemistries. Effects of steel composition and process conditions on case depth and structure were determined. It was reported that case depth was increased by addition of C and MO and the amount of ycarbonitride was increased by increased concentration of Cu and Ni. The case depths were 10 to 25 pm and Vickers hardness was 500 to 800.
LAPPING OF PM MATERIALS A.Barylski. (Technical University of Gdansk, Gdansk , Poland.) A study of the rate of material removal in lapping PM materials was described. An artificial material was used as a standard and effects of pressure and size and type of abrasive, SIC and syn-
thetic corundum, were investigated. The SIC was reported to be better for hard materials and corundum for soft sintered materials. PROPERTIES OF INDUCTION HARDENED PM STEEL PARTS M.Rosso et al. (Polytechnic of Torino, Torino, Italy.) Induction hardening of steel parts was discussed and it was noted that closer control is required for sintered parts than for wrought steel. Induction hardening of sintered parts was investigated. The influence of alloy content was evaluated.
Testing measurement and control MICRO-COMPUTER TOMOGRAPHY FOR CHARACTERIZATION OF INNER VOLUME OF PM PARTS K.Pischang et al. (Dresden University of Technology, Dresden, Germany.) Defects, and their detection in PM parts, were discussed with reference to causes and difficulties in characterizing the inner volume. It was shown that the inner volume can be visualized by the use of micro-computer tomography. This allows measurement of density distribution. Examples were given. The technique was described and discussed. POROSITY DISTRIBUTION IN PM STEELS R.Norling. (Lund University, Lund, Sweden.) Porosity in PM steels was investigated by quantitative metallography on 16 sucessive polished sections, each 0.1 mm deeper into the specimen than the last. Porosities of 4 to 12% were found. The distribution of porosity differed for each steel. Fe-2%Cu-0.8% showed low porosity at corners and at the centre. Fe4%Ni-1.5%Cu-0.5%Mo-0.5%C had low porosity at edges and centre. ASSESSMENT OF GREEN COMPACTS BY 3-DIMENSIONAL TOMOGRAPHY T.Rabe et al. (Federal Inst. for Materials Research and Testing, Germany.) Occurrence of density gradients and cracks in green compacts was discussed, These may go undetected. It was shown that 3D X-ray tomography can be used to study density distribution in green parts. Examples of use of the technique were presented. DIRECT CURRENT POTENTIAL DROP METHOD FOR ASSESSMENT OF GREEN COMPACTS P.Luukkonen, T.Ericsson. University, Sweden.)
(Linkopings
The need for an on-line nondestructive test method for detection of cracks in green compacts was noted. It was shown that a Direct Current Potential Drop technique can be used. Development of the method to separate the crack signal from other factors was outlined and an optimum design of test probe was described. Use of the technique on a twolevel part, made by double action compaction with split punches was presented.
Intermetallic
materials
FABRICATION OF TITANIUM-NICKEL ALLOY BY SPARK PLASMA SINTERING H.Kyogoku et al. (Kinki University, Higashihiroshima, Japan.) Effects of process conditions on mechanical properties and shape memory characteristics of spark plasma sintered and heat treated TiNi, made from gas atomized Fe and carbonyl Ni powders, were investigated. 98.5%density was attained. Sintering, for 40 minutes at 95O”C, with the heat treatment gave a significantly homogeneous microstructure. The PM alloy exhibited shape memory characteristics but the mechanical properties were inferior to those of wrought alloys. SHAPE FORMING SPARK PLASMA SINTERING OF TITANIUM ALUMINIDE FOR AUTOMOBILE VALVE T.Abe et al. (Tohoku National Industrial Research Inst., Sendai, Japan.) TiAl powders were synthesized by mechanical alloying or by combustion synthesis of mixed powders, and consolidated by spark plasma sintering. Three point bend strengths were over 1 GPa for mechanically alloyed powder and 670 MPa for the combustion synthesized material. Sintered rods 5 cm long and 8 mm in diameter were produced and joined. The valve shape was made by further addition of TiAl powder and sinter joining to the rod. Near full density was reported.
Metal
matrix
composites
CHARACTERIZATION OF ALUMINIUM MATRIX COMPOSITES WITH INTERMETALLIC POWDER PARTICLES M.Lieblich, B.Torres-Barreiro. (Insamet, Spain.) It was reported that Al matrix composites, reinforced with particulate intermetallic compounds, in various proportions and particle sizes, had been prepared from elemental Al and intermetallic compound powders. Structures of consolidated materials were investigated as functions of material and process parameters. Mechanical properties and
MPR May 2000
49