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Effect of sintering on dimensional accuracy of machined green parts
The filters were fabricated by a fibre dressing technique and sintered into various shapes. Fe-Cr-Al and N&Al fibre materials were made into filters with porosities of 60 to 97%. Characteristics of the filters were described. FORMATION OF DENDRITIC METAL POWDERS C.J.Vroman, R.Zeller. (Millipore Corp, USA. ) It was noted that metal filters, made from powder, require dendritic powders. A method of making dendritic powders from spherical or irregular powders, to reduce the apparent density of the powder, was described. The non-dendritic powders were lightly sintered, broken up and sieved to a controlled size distribution. It was shown that the converted powder could be used to make parts with lower density than was possible with the original non-dendritic powder.
Hard metals and wear resistant materials EFFECT OF HEAT TREATMENT ON PROPERTIES OF SINTERED HIGH SPEEDSTEEL O.C.S.Ribeiro et al. (IPEN-CNEN/SP, Brazil.) Production and mechanical properties of sintered high speed steel were discussed. The effects of heat treatment on properties and machining performance of PM T15 high speed steel were investigated. Cutting performance was correlated with mechanical properties. MICROSTRUCTURE AND PROPERTIES OF LIQUID PHASE SINTERED TUNGSTEN ALLOYS F.A.Khalid, M.R.Bhati. (Faculty of Metallurgy and Materials Engineering, Pakistan.) Structure and properties of liquid phase sintered W-Co-Ni-Fe, W-Ni-Fe and W-Ni-Cu alloys were investigated and compared. W-Co-Ni-Fe had the best properties. Brittle failure was observed and this was attributed to segregation. W-W and W-matrix boundaries were examined to assess the role of impurities in the sintered alloys. CHARACTERISTICS OF METALLIC BINDING POWDERS BEFORE AND AFTER HOT PRESSING R.Curic et al. (Inst. for Technology of Nuclear and Mineral Raw Materials, Yugoslavia. ) Effects of powder shape and particle size distribution, in powders used to bind diamond powder in the production of cutting tools by hot pressing, were investigated. Two Co powders, with
acceptable impurity contents, and one Fe-Co-bronze powder were used in the study. These differed in morphology and particle size distribution. Characteristics of powders and hot pressed materials were described. There were interactions between powder constituents during processing and a model for these was presented.
PM98. The following Abstracts are from papers that were presented at the 1998 Powder Metallurgy World Congress, which was held in Granada, Spain, in October 1998.
Electrical materials
and magnetic
Machinability
IRON-RESIN COMPOSITE MATERIALS FOR AC MAGNETIC APPLICATIONS
EVALUATION OF REDUCIBILITY OF OXIDE PARTICLES FOUND IN POWDERS AND PM PARTS
M.J.Battison, CGelinas. (Quebec Metal Powders Ltd, Quebec, Canada.) Resin bonded Fe magnetic materials were reviewed. Pure Fe powders are used and these are insulated from each other by an oxide film and/or a film of thermoset resin. It was shown that composition and process conditions enable properties to be matched to applications for example by the use of coarse or fine powders. Effects of composition and process conditions on properties were discussed.
B.Deschenes et al. (Domfer Metal Powders Ltd, Canada.) Effects of oxide particles and nonmetallic inclusions on properties of PM parts were reviewed. Predictions concerning reduction of oxide inclusions can be made using thermodynamics but real cases are often too complex for modelling. An experimental investigation of reducibility of oxides in metal powders and PM parts was described. The oxides were identified by analytical electron microscopy and tests to reduce these phases were carried out. EFFECT OF MANGANESE SULPHIDE PARTICLE SIZE ON PM VALVE GUIDES (Sintering S.E.Maloy, W.K.Fricke. Technologies Inc, USA. ) Makers of PM valve guides were reported to be under pressure to supply parts that permit longer cutting tool lives at end-users. Assembly into engines and final machining of valve guides was described. A study of the effect of particle size of MnS, added to enhance machinability, on tool life was studied. Effects of MnS on properties and structure of the valve guides were evaluated. EFFECT OF SINTERING ON DIMENSIONAL ACCURACY OF MACHINED GREEN PARTS I.Shareef et al. (Bradley University, USA.) It was noted that many PM parts require some machining and that the higher densities and green strengths recently attained had allowed green parts to be machined. An investigation of the effects of green machining on the dimensional accuracy of sintered parts was described. Four powder mixtures were warm pressed to two densities and the eight samples were drilled in the green state. The sintered parts were evaluated for dimensional accuracy and surface finish. Ni was shown to increase contraction during sintering.
A SINTERED MAGNETIC CORE FOR AN IGNITION COIL I.Kulszewicz et al. (Polmo Lomianki SA, Lomianki, Poland.) Use of PM to make parts for automotive ignition coils was outlined. Product design, processing and properties were discussed. Comparison was made between PM parts and parts made by other methods. It was suggested that use of PM can reduce costs. STRUCTURES OF POWDERS AND GREEN COMPACTS OF NICKEL-ZINC FERRITES
M.I.Toacsan et al. (Inst. of Materials Physics, Bucharest, Romania.) A study intended to correlate characteristics of Ni-Zn ferrite powders with those of green compacts was described. These results were correlated with the magnetic properties of polycrystalline sintered ferrite materials. SINTERRD TUNGSTEN COPPER PARTS
CARRIDE-
D.Tarata, P.Ileana. (University of Craiova, Craiova, Romania.) Mechanical and physical properties of WC-Cu cermets, made by liquid phase sintering, were discussed. Measurements of strength, thermal and electrical conductivity and wear properties were presented. EFFECT OF ATTRITION MILLING PERFORMANCE OF TUNGSTRNSILVER SWITCH CONTACTS
ON
Z.Aslanoglu et al. (Sakarya University, Adapazari, Turkey.) It was reported that composite W25wt%Ag powders had been prepared by
MPR May 1999 41
Hard metals and wear resistant materials EFFECT OF HEAT TREATMENT ON PROPERTIES OF SINTERED HIGH SPEEDSTEEL O.C.S.Ribeiro et al. (IPEN-CNEN/SP, Brazil.) Production and mechanical properties of sintered high speed steel were discussed. The effects of heat treatment on properties and machining performance of PM T15 high speed steel were investigated. Cutting performance was correlated with mechanical properties. MICROSTRUCTURE AND PROPERTIES OF LIQUID PHASE SINTERED TUNGSTEN ALLOYS F.A.Khalid, M.R.Bhati. (Faculty of Metallurgy and Materials Engineering, Pakistan.) Structure and properties of liquid phase sintered W-Co-Ni-Fe, W-Ni-Fe and W-Ni-Cu alloys were investigated and compared. W-Co-Ni-Fe had the best properties. Brittle failure was observed and this was attributed to segregation. W-W and W-matrix boundaries were examined to assess the role of impurities in the sintered alloys. CHARACTERISTICS OF METALLIC BINDING POWDERS BEFORE AND AFTER HOT PRESSING R.Curic et al. (Inst. for Technology of Nuclear and Mineral Raw Materials, Yugoslavia. ) Effects of powder shape and particle size distribution, in powders used to bind diamond powder in the production of cutting tools by hot pressing, were investigated. Two Co powders, with
acceptable impurity contents, and one Fe-Co-bronze powder were used in the study. These differed in morphology and particle size distribution. Characteristics of powders and hot pressed materials were described. There were interactions between powder constituents during processing and a model for these was presented.
PM98. The following Abstracts are from papers that were presented at the 1998 Powder Metallurgy World Congress, which was held in Granada, Spain, in October 1998.
Electrical materials
and magnetic
Machinability
IRON-RESIN COMPOSITE MATERIALS FOR AC MAGNETIC APPLICATIONS
EVALUATION OF REDUCIBILITY OF OXIDE PARTICLES FOUND IN POWDERS AND PM PARTS
M.J.Battison, CGelinas. (Quebec Metal Powders Ltd, Quebec, Canada.) Resin bonded Fe magnetic materials were reviewed. Pure Fe powders are used and these are insulated from each other by an oxide film and/or a film of thermoset resin. It was shown that composition and process conditions enable properties to be matched to applications for example by the use of coarse or fine powders. Effects of composition and process conditions on properties were discussed.
B.Deschenes et al. (Domfer Metal Powders Ltd, Canada.) Effects of oxide particles and nonmetallic inclusions on properties of PM parts were reviewed. Predictions concerning reduction of oxide inclusions can be made using thermodynamics but real cases are often too complex for modelling. An experimental investigation of reducibility of oxides in metal powders and PM parts was described. The oxides were identified by analytical electron microscopy and tests to reduce these phases were carried out. EFFECT OF MANGANESE SULPHIDE PARTICLE SIZE ON PM VALVE GUIDES (Sintering S.E.Maloy, W.K.Fricke. Technologies Inc, USA. ) Makers of PM valve guides were reported to be under pressure to supply parts that permit longer cutting tool lives at end-users. Assembly into engines and final machining of valve guides was described. A study of the effect of particle size of MnS, added to enhance machinability, on tool life was studied. Effects of MnS on properties and structure of the valve guides were evaluated. EFFECT OF SINTERING ON DIMENSIONAL ACCURACY OF MACHINED GREEN PARTS I.Shareef et al. (Bradley University, USA.) It was noted that many PM parts require some machining and that the higher densities and green strengths recently attained had allowed green parts to be machined. An investigation of the effects of green machining on the dimensional accuracy of sintered parts was described. Four powder mixtures were warm pressed to two densities and the eight samples were drilled in the green state. The sintered parts were evaluated for dimensional accuracy and surface finish. Ni was shown to increase contraction during sintering.
A SINTERED MAGNETIC CORE FOR AN IGNITION COIL I.Kulszewicz et al. (Polmo Lomianki SA, Lomianki, Poland.) Use of PM to make parts for automotive ignition coils was outlined. Product design, processing and properties were discussed. Comparison was made between PM parts and parts made by other methods. It was suggested that use of PM can reduce costs. STRUCTURES OF POWDERS AND GREEN COMPACTS OF NICKEL-ZINC FERRITES
M.I.Toacsan et al. (Inst. of Materials Physics, Bucharest, Romania.) A study intended to correlate characteristics of Ni-Zn ferrite powders with those of green compacts was described. These results were correlated with the magnetic properties of polycrystalline sintered ferrite materials. SINTERRD TUNGSTEN COPPER PARTS
CARRIDE-
D.Tarata, P.Ileana. (University of Craiova, Craiova, Romania.) Mechanical and physical properties of WC-Cu cermets, made by liquid phase sintering, were discussed. Measurements of strength, thermal and electrical conductivity and wear properties were presented. EFFECT OF ATTRITION MILLING PERFORMANCE OF TUNGSTRNSILVER SWITCH CONTACTS
ON
Z.Aslanoglu et al. (Sakarya University, Adapazari, Turkey.) It was reported that composite W25wt%Ag powders had been prepared by
MPR May 1999 41