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Manufacture of metal objects by selective laser sintering
The following topics were discussed: the adaptation of the Komanian hardmetal industry to a market economy, raw material resources and possibilities for further developments in hardmetals production.
Synthesis FLUIDIZED PROCESSING MATERIALS
BED REACTOR OF MAGNETIC
S.C.Deevi et al. (Philip Morris inc., USA.) Production and properties, particularly magnetic, of carbides and nitrides of Fe were discussed with regard to the use of fluidized bed technology. It was reported that Fe carbides and nitrides had been prepared from oxide. The method was shown to provide a viable production process. Process parameters properties were described TITANIUM POWDERS MILLING
and
powder
OXY-GARBO-NITRIDE PRODUCED BY REACTIVE
B.Ramirez et al. (Inst. Politecnico National, Mexico.) Application of reactive milling to compound synthesis was discussed. Investigations of attritor milling of Ti and Ti-graphite in air, N and NH3 were described. The resultant powders were comprehensively characterized. Powder were shown to be similar to TiN, TIC,, TiO, Ti(O,N) and Ti(C,N) depending on initial powder composition and milling atmosphere with nm sizes. A few samples were reported to be pyrophoric on exposure to air. KINETICS OF REACTIVE SYNTHESIS OF NICKEL ALIJMINIDE FROM DENSE ELEMENTAL POWDER BLENDS Y.Gutmanas et al. (Israel Inst. of Technology, Haifa, Israel.) Detailed analysis of the solid state process that leads to synthesis of NiAl in dense elemental powder blends was presented and discussed with reference to proces parameters, powder characteristics and phase synthesis. Interface barriers to diffusion were taken into account. It was shown that conditions can be selected to control the reaction rates.
Densification
control
DISTORTION CONTROL FOR PM BASED RAPID PROTOTYPING OF ADVANCED MATERIAL COMPONENTS S.J.Rock, W.Z.Misiolek. (Rensselaer Polytechnic Inst., Troy, New York, USA) Distortion of parts during processing was discussed with respect to causes and effects. It was noted that in short-run and prot,otyping t,here is often severe distortion.
Researches aimed at limiting distortion by analysis of part shapes and process parameters were described. A process which used pre-distortion to cancel effects of process distortion was considered with regard to the constraints of rapid prototyping. The technique, it was suggested, could be applicable to other PM production.
Mechanical, magnetic and corrosion properties of stainless steels were reviewed with reference to admixed materials. An investigation of the properties of steels with 9, IO or ll%Cr was described. Steels were prepared from atomized Fe and fine Cr powders, compacted at a range of pressures and sintered at 1260°C for 2 hours in H. properties were measured and comparison
CONSOLIDATION AND RESIDUAL STRESSES IN COMPOSITE POWDER COMPACTS
was made with 410 stainless from prealloyed powder.
AZavaliangos, J.Wen. (Drexel University, USA.) The problems of densification of composite powders mixtures was discussed with reference to a number of PM t,echniques and materials. The mechanics of consolidation were examined, in particular the effects of volume fractions and relative strengths of the components and the quality of mixing. Mixing is shown to influence consolidation pressure. The presence of residual stresses was predicted and these were shown to affect mechanical properties. Factors influencing the development of residual stresses were discussd. FLOW FORMING PREFORMS
OF SINTERED
METAL
MICROSTRUCTURAL OF BORON ALLOYED STAINLESS STEEL
steel
made
OPTIMIZATION AUSTENITIC
AMolinari et al. (University of Trento, Italy.) The functions of B in stainless steel, formation of a cutcctic, reduction of oxides by elemental B and formation of liquid R oxide, in increasing sintered density was discussed. It was noted that corrosion properties may be impaired by formation of a Cr rich constituent at grain boundaries. It was reported that a good quality alloy was made by sintering PM
at 1240°C in H.
laser manufacturing
LASER AIDED OF METALS
DIRECT
DEPOSITION
P.Viorel et al. (University ‘Dunarea de Jos’, Romania.) Flow forming, used to make thin walled circular parts with a high 1ength:diameter ratio, was outlined. Application of the technique to deform sintered metal preforms was investigated for different Fe powders. Cups were made by CIP and sintered. Flow forming, using steel balls, was carried out. Influence of process variables on part properties was determined. The technique was shown to be viable, within limits depending on process conditions, to give dimensional accuracy and good surface finish.
J.Koch et al. (University of Illinois, USA.) Applications of lasers were discussed. It was reported that manufacture of various shapes had been aided by use of lasers and that near 100% density had been attained.
Stainless
sintering process had been used to make 3dimensional objects. The laser beam is scanned over a powder bed. Under computer control the part is built up by sucessive scans. Fe-Cu parts were made from a polymer coated Fe powder. The parts were debound, sintered and infiltrated with Cu. Recent advances were described with an account of the effects of powder properties and process conditions.
steels
EXPANSION OF PM INTO EXHAUST SYSTEMS
AUTOMOTIVE
J.H.Mandel, T.M.Cadle. (Zenith Sintered Products Inc., Germantown, USA) The possible extension of PM products into automotive exhaust systems was discussed with reference to problems of service conditions and of part fabrication. Components were described and service conditions outlined. A programme to provide data for materials selection, design and manufacture was described. INFLUENCE OF CHROMIUM CONTENT ON MAGNETIC AND CORROSION PROPERTIES OF STAINLESS STEELS K.H.Moyer et al. (Magna-Tech tories, USA.)
PM Labora-
Process conditions were described. Properties and microstructures of materials prepared by laser aided direct metal deposition were described. MANUFACTURE BY SELECTIVE
OF METAL OBJECTS LASER SINTERING
Ulakshminarayan, USA.) It was reported
SOLID FREEFORM POWDERS USING
K.McAlea, that
(DIM
a selective
Carp, laser
FABRICATION OF LASER PROCESSING
D.Bourell et al. (University of Texas, USA) Recent devclopmcnts in the use of a range of laser techniques in PM processing were outlined. Techniques and materials problems in selective laser sintering, selective laser reactive sintering and selected area laser deposition vapour infiltration were discussed with some examples.
MPR July/August
1997
43
Synthesis FLUIDIZED PROCESSING MATERIALS
BED REACTOR OF MAGNETIC
S.C.Deevi et al. (Philip Morris inc., USA.) Production and properties, particularly magnetic, of carbides and nitrides of Fe were discussed with regard to the use of fluidized bed technology. It was reported that Fe carbides and nitrides had been prepared from oxide. The method was shown to provide a viable production process. Process parameters properties were described TITANIUM POWDERS MILLING
and
powder
OXY-GARBO-NITRIDE PRODUCED BY REACTIVE
B.Ramirez et al. (Inst. Politecnico National, Mexico.) Application of reactive milling to compound synthesis was discussed. Investigations of attritor milling of Ti and Ti-graphite in air, N and NH3 were described. The resultant powders were comprehensively characterized. Powder were shown to be similar to TiN, TIC,, TiO, Ti(O,N) and Ti(C,N) depending on initial powder composition and milling atmosphere with nm sizes. A few samples were reported to be pyrophoric on exposure to air. KINETICS OF REACTIVE SYNTHESIS OF NICKEL ALIJMINIDE FROM DENSE ELEMENTAL POWDER BLENDS Y.Gutmanas et al. (Israel Inst. of Technology, Haifa, Israel.) Detailed analysis of the solid state process that leads to synthesis of NiAl in dense elemental powder blends was presented and discussed with reference to proces parameters, powder characteristics and phase synthesis. Interface barriers to diffusion were taken into account. It was shown that conditions can be selected to control the reaction rates.
Densification
control
DISTORTION CONTROL FOR PM BASED RAPID PROTOTYPING OF ADVANCED MATERIAL COMPONENTS S.J.Rock, W.Z.Misiolek. (Rensselaer Polytechnic Inst., Troy, New York, USA) Distortion of parts during processing was discussed with respect to causes and effects. It was noted that in short-run and prot,otyping t,here is often severe distortion.
Researches aimed at limiting distortion by analysis of part shapes and process parameters were described. A process which used pre-distortion to cancel effects of process distortion was considered with regard to the constraints of rapid prototyping. The technique, it was suggested, could be applicable to other PM production.
Mechanical, magnetic and corrosion properties of stainless steels were reviewed with reference to admixed materials. An investigation of the properties of steels with 9, IO or ll%Cr was described. Steels were prepared from atomized Fe and fine Cr powders, compacted at a range of pressures and sintered at 1260°C for 2 hours in H. properties were measured and comparison
CONSOLIDATION AND RESIDUAL STRESSES IN COMPOSITE POWDER COMPACTS
was made with 410 stainless from prealloyed powder.
AZavaliangos, J.Wen. (Drexel University, USA.) The problems of densification of composite powders mixtures was discussed with reference to a number of PM t,echniques and materials. The mechanics of consolidation were examined, in particular the effects of volume fractions and relative strengths of the components and the quality of mixing. Mixing is shown to influence consolidation pressure. The presence of residual stresses was predicted and these were shown to affect mechanical properties. Factors influencing the development of residual stresses were discussd. FLOW FORMING PREFORMS
OF SINTERED
METAL
MICROSTRUCTURAL OF BORON ALLOYED STAINLESS STEEL
steel
made
OPTIMIZATION AUSTENITIC
AMolinari et al. (University of Trento, Italy.) The functions of B in stainless steel, formation of a cutcctic, reduction of oxides by elemental B and formation of liquid R oxide, in increasing sintered density was discussed. It was noted that corrosion properties may be impaired by formation of a Cr rich constituent at grain boundaries. It was reported that a good quality alloy was made by sintering PM
at 1240°C in H.
laser manufacturing
LASER AIDED OF METALS
DIRECT
DEPOSITION
P.Viorel et al. (University ‘Dunarea de Jos’, Romania.) Flow forming, used to make thin walled circular parts with a high 1ength:diameter ratio, was outlined. Application of the technique to deform sintered metal preforms was investigated for different Fe powders. Cups were made by CIP and sintered. Flow forming, using steel balls, was carried out. Influence of process variables on part properties was determined. The technique was shown to be viable, within limits depending on process conditions, to give dimensional accuracy and good surface finish.
J.Koch et al. (University of Illinois, USA.) Applications of lasers were discussed. It was reported that manufacture of various shapes had been aided by use of lasers and that near 100% density had been attained.
Stainless
sintering process had been used to make 3dimensional objects. The laser beam is scanned over a powder bed. Under computer control the part is built up by sucessive scans. Fe-Cu parts were made from a polymer coated Fe powder. The parts were debound, sintered and infiltrated with Cu. Recent advances were described with an account of the effects of powder properties and process conditions.
steels
EXPANSION OF PM INTO EXHAUST SYSTEMS
AUTOMOTIVE
J.H.Mandel, T.M.Cadle. (Zenith Sintered Products Inc., Germantown, USA) The possible extension of PM products into automotive exhaust systems was discussed with reference to problems of service conditions and of part fabrication. Components were described and service conditions outlined. A programme to provide data for materials selection, design and manufacture was described. INFLUENCE OF CHROMIUM CONTENT ON MAGNETIC AND CORROSION PROPERTIES OF STAINLESS STEELS K.H.Moyer et al. (Magna-Tech tories, USA.)
PM Labora-
Process conditions were described. Properties and microstructures of materials prepared by laser aided direct metal deposition were described. MANUFACTURE BY SELECTIVE
OF METAL OBJECTS LASER SINTERING
Ulakshminarayan, USA.) It was reported
SOLID FREEFORM POWDERS USING
K.McAlea, that
(DIM
a selective
Carp, laser
FABRICATION OF LASER PROCESSING
D.Bourell et al. (University of Texas, USA) Recent devclopmcnts in the use of a range of laser techniques in PM processing were outlined. Techniques and materials problems in selective laser sintering, selective laser reactive sintering and selected area laser deposition vapour infiltration were discussed with some examples.
MPR July/August
1997
43