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Modelling compaction and sintering of rhenium
Destructive and non-destructive tests were reviewed. Quantitative resonant inspection, correlated with destructive testing, is a useful production line non-destructive test. It was noted that many ND tests give only an indication of a flaw with no measurable structural weakness. Many failed parts have invisible defects. Structural analysis from resonance was shown to discriminate on the basis of structural integrity and material properties.
Development of low-coercivity magnets from sponge iron powder A.Bose et al. (Materials Processing Inc., USA.)
It was reported that a soft magnetic material had been produced from high quality sponge Fe powder, by pressing, high temperature sintering and heat treatment, to give a high density, large grain size material with low C, S and P contents. Average coercivity was 1.60e. Efforts to lower this, by reduction in %0 and porosity, were reported to be in progress.
Detection of cracks and sizing using eddy current testing A.Alencar et al. (National Nuckar Energ-~ Cmnmision, Brazil.)
Eddy current testing for detection of surface defects and materials characterisation was described and discussed. Factors affecting eddy currents were identified. A study of use of eddy currents tests for detection of cracks was described.
Refractory metals
-
rhenium
Advances in powder metallurgy of rhenium
Modelling hot isostatic pressing of rhenium C.Trybus et al. Concurrent Technologies Inc., USA.)
A model for HIP of spherical Re powder was described. Power law creep was used to approximate the constitutive behaviour of the powder. A finite element program was used, calibrated by use of interrupted HIP tests and high temperature compression tests of full density Re. Further HIP tests at other conditions were used to verify final density and displacement results of the model.
Recent developments in use of PM for Re materials were reported. These included cold isostatic pressing of complex shapes, development of high-density spherical Re powder, vacuum plasma spraying and direct hot isostatic pressing of near net shape parts. These innovations were shown to reduce costs, processing time and improve yield in processing PM Re and Re alloy parts.
Modelling compaction and sintering of rhenium
D.E.Alman et al. (US Dept. ofEnergy, USA.)
Use of PM to fabricate Fe based wear-resistant composites, starting from Fe-Tic, was outlined. Processing of elemental Fe-Ti-Cr-C mixtures, by hot pressing to full density, was outlined. Carbides were synthesised during processing. Effects of composition and process conditions on structure and wear resistance were discussed. It was shown that microstructure could be controlled. Surface laser melting was used to produce a fine structured surface layer with improved wear resistance.
Effects of process conditions on structure and abrasive wear of PM tool steels ofEnergy,USA.)
The role of PM in fabrication of fine structured tool steels was discussed with particular reference to wear properties. A study of the relationships between wear resistance, microstructure and heat treatment of four widely differing tool steels, using two-body abrasion and scratch tests, was described. Wear resistance was reviewed with regard to microstructural features.
Wear resistance of copper-graphite composites A.A.Sanad
et al.
(El-Azhar
University,
Cairo,
Egypt.) C.Tvybus et al. Concurrent Technologies Inc., USA.) It was reported
that a finite element model had been used to simulate densification of Re during die pressing and cold isostatic pressing. Constitutive behaviour was approximated by use of earlier metal powder models and calibration was from results of triaxial tests. The model was validated by comparison of predicted and measured values of density from die compaction. Model predictions of density distribution and data for a master-sintering curve were presented.
88
MPR July/August
2002
S.H.Luk, K.S.Nmsimhan. (Hoeganm Colgoration, USA.)
Advantages arising from use of binder treated powder mixtures were discussed with regard to improvements made in green properties. Recent developments in binder treatment technology and production were reviewed.
L. G .Roy,
Processing structure and abrasive wear of iron-chromium-titanium carbide composites
et al. (US Dept.
Enhancement of green strength for increase in process robustness
Improvement in green properties by mixing techniques
Wear-resistant materials
D.E.Almn
.l.J.Doum et nl. (Rhenium Alloys Inc., USA.)
Improvement of green properties
Wear properties of Cu-C composites, made from graphite or Cu-coated graphite powders, were investigated in air using dry pin-on-ring test rigs. Wear rates of composites made from coated graphite powder were the lower at low loads. There was severe wear at loads of 120N in pure Cu. The composites could resist severe wear up to 450N. Wear mechanisms for Cu were identified as oxidation, seizure and fusion. The reduced wear of composites was attributed to a lubrication effect due to graphite.
R L.Edwnrds. (Lit&ford Day Inc., USA.)
It was noted that the mixing of powders affects the green properties of PM parts, and that green properties can be improved by attention to the mixing process. A study of lubricant reduction in pilot plant projects, where all green and sintered property data were recorded was described.
Steels containing manganese sulphide Optimisation of pre-alloyed steel-manganese sulphide powders C.Blais et al. (Domfer Metal Powders, Canada.)
The role of MnS in enhancing machinability of steel was discussed with regard to concentration of MnS and properties of powder and processed materials. An investigation of the effects of %MnS and ratio Mn:S was described. The object was to optimise the Mn and S contents of pre-alloyed MnS steels. Results were reviewed with regard to microstructural charac, teristics of powders and sintered materials.
Machinability and fatigue of pm-alloyed free-cutting steel powders M.Haasetal. (Kob&oMer$Pcn&ofAnwicalw.,
USA.)
Development of pre-alloyed free machining powder steels with improved fatigue strength and machinability, compared with powder forged FC0208-MnS, was reported. Tensile, fatigue and machining properties of the novel steel, processed by a press-and-sinter route, were investigated.
Relationship between machinability additives and machining parameters O.Mars, C.Berg. (H6gmiis AB, Haganiis, Sweden.) It was noted that the choice of machinability enhancers depends much on machining conditions. It was noted that there are significant differences in tool life when effects of different additives were investigated and an investigation was described. A range of ferrous materials, in different structural conditions with various types and concentrations of additives were studied in drilling and turning. It was shown that selection of an optimum machinabilty enhancer can reduce costs.
www.metal-powder.net
Development of low-coercivity magnets from sponge iron powder A.Bose et al. (Materials Processing Inc., USA.)
It was reported that a soft magnetic material had been produced from high quality sponge Fe powder, by pressing, high temperature sintering and heat treatment, to give a high density, large grain size material with low C, S and P contents. Average coercivity was 1.60e. Efforts to lower this, by reduction in %0 and porosity, were reported to be in progress.
Detection of cracks and sizing using eddy current testing A.Alencar et al. (National Nuckar Energ-~ Cmnmision, Brazil.)
Eddy current testing for detection of surface defects and materials characterisation was described and discussed. Factors affecting eddy currents were identified. A study of use of eddy currents tests for detection of cracks was described.
Refractory metals
-
rhenium
Advances in powder metallurgy of rhenium
Modelling hot isostatic pressing of rhenium C.Trybus et al. Concurrent Technologies Inc., USA.)
A model for HIP of spherical Re powder was described. Power law creep was used to approximate the constitutive behaviour of the powder. A finite element program was used, calibrated by use of interrupted HIP tests and high temperature compression tests of full density Re. Further HIP tests at other conditions were used to verify final density and displacement results of the model.
Recent developments in use of PM for Re materials were reported. These included cold isostatic pressing of complex shapes, development of high-density spherical Re powder, vacuum plasma spraying and direct hot isostatic pressing of near net shape parts. These innovations were shown to reduce costs, processing time and improve yield in processing PM Re and Re alloy parts.
Modelling compaction and sintering of rhenium
D.E.Alman et al. (US Dept. ofEnergy, USA.)
Use of PM to fabricate Fe based wear-resistant composites, starting from Fe-Tic, was outlined. Processing of elemental Fe-Ti-Cr-C mixtures, by hot pressing to full density, was outlined. Carbides were synthesised during processing. Effects of composition and process conditions on structure and wear resistance were discussed. It was shown that microstructure could be controlled. Surface laser melting was used to produce a fine structured surface layer with improved wear resistance.
Effects of process conditions on structure and abrasive wear of PM tool steels ofEnergy,USA.)
The role of PM in fabrication of fine structured tool steels was discussed with particular reference to wear properties. A study of the relationships between wear resistance, microstructure and heat treatment of four widely differing tool steels, using two-body abrasion and scratch tests, was described. Wear resistance was reviewed with regard to microstructural features.
Wear resistance of copper-graphite composites A.A.Sanad
et al.
(El-Azhar
University,
Cairo,
Egypt.) C.Tvybus et al. Concurrent Technologies Inc., USA.) It was reported
that a finite element model had been used to simulate densification of Re during die pressing and cold isostatic pressing. Constitutive behaviour was approximated by use of earlier metal powder models and calibration was from results of triaxial tests. The model was validated by comparison of predicted and measured values of density from die compaction. Model predictions of density distribution and data for a master-sintering curve were presented.
88
MPR July/August
2002
S.H.Luk, K.S.Nmsimhan. (Hoeganm Colgoration, USA.)
Advantages arising from use of binder treated powder mixtures were discussed with regard to improvements made in green properties. Recent developments in binder treatment technology and production were reviewed.
L. G .Roy,
Processing structure and abrasive wear of iron-chromium-titanium carbide composites
et al. (US Dept.
Enhancement of green strength for increase in process robustness
Improvement in green properties by mixing techniques
Wear-resistant materials
D.E.Almn
.l.J.Doum et nl. (Rhenium Alloys Inc., USA.)
Improvement of green properties
Wear properties of Cu-C composites, made from graphite or Cu-coated graphite powders, were investigated in air using dry pin-on-ring test rigs. Wear rates of composites made from coated graphite powder were the lower at low loads. There was severe wear at loads of 120N in pure Cu. The composites could resist severe wear up to 450N. Wear mechanisms for Cu were identified as oxidation, seizure and fusion. The reduced wear of composites was attributed to a lubrication effect due to graphite.
R L.Edwnrds. (Lit&ford Day Inc., USA.)
It was noted that the mixing of powders affects the green properties of PM parts, and that green properties can be improved by attention to the mixing process. A study of lubricant reduction in pilot plant projects, where all green and sintered property data were recorded was described.
Steels containing manganese sulphide Optimisation of pre-alloyed steel-manganese sulphide powders C.Blais et al. (Domfer Metal Powders, Canada.)
The role of MnS in enhancing machinability of steel was discussed with regard to concentration of MnS and properties of powder and processed materials. An investigation of the effects of %MnS and ratio Mn:S was described. The object was to optimise the Mn and S contents of pre-alloyed MnS steels. Results were reviewed with regard to microstructural charac, teristics of powders and sintered materials.
Machinability and fatigue of pm-alloyed free-cutting steel powders M.Haasetal. (Kob&oMer$Pcn&ofAnwicalw.,
USA.)
Development of pre-alloyed free machining powder steels with improved fatigue strength and machinability, compared with powder forged FC0208-MnS, was reported. Tensile, fatigue and machining properties of the novel steel, processed by a press-and-sinter route, were investigated.
Relationship between machinability additives and machining parameters O.Mars, C.Berg. (H6gmiis AB, Haganiis, Sweden.) It was noted that the choice of machinability enhancers depends much on machining conditions. It was noted that there are significant differences in tool life when effects of different additives were investigated and an investigation was described. A range of ferrous materials, in different structural conditions with various types and concentrations of additives were studied in drilling and turning. It was shown that selection of an optimum machinabilty enhancer can reduce costs.
www.metal-powder.net