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Determination of machinablity of PM materials by drilling tests
Pressing MODEL FOR THERMAL ANALYSIS IN COLD IJNIAXIAL POWDER COMPACTION A.K.Ariffin, D.T.Gethin. (University of Wales, Swansea, Wales, UK.) Powder Metall., Vol 41, No 2, 1998,123-129. A thermal and mechanical analysis of cold compaction is presented. This is coupled with friction, heat of compaction and local density. It is shown that thermal conductivity increases with density Effects of frictional heating and temperature rise are demonstrated. Temperature rise increased with increase in compaction speed. Heat transfer between powder and tooling is shown to be important.
Fundamentals PARTICLE OVERLAP AND SEGREGATION PROBLEMS IN ONLINE COARSE PARTICLE SIZE MEASUREMENT C.L.Lin et al. (University of Utah, Salt Lake City, USA.) Powder Technol., Vol 98, No 1,1998, l-12. It is noted that particle overlap and segregation are factors that adversely affect the accuracy of image based particle size measurement systems. An empirical factor may be used to correct this but is of limited value. Simulation studies, using Monte Carlo methods to provide a base for image based particle size measurement systems and reliable correction factors, are described. Findings from the computer simulation were used to design a drop-box experiment. The results of the studies are shown to facilitate use of image based methods for on-line measurement of coarse particle sizes. USE OF PROJECTED AREA DISTRIBUTION FUNCTIONS IN PARTICLE SHAPE MEASUREMENT D.J.Brown, G.T.Vickers. (University of Sheffield, Sheffield, UK.) Powder Technol., Vol 98, No 3,1998,250-257. It is noted that measurement of particle shape by image analysis and light scattering depends on projected area. Non-spherical particles exhibit ranges of values for projected area and perimeter. Distribution of these variables and mean values are indicative of specific shapes. An investigation to determine
the number of results needed to give good agreement with actual distribution is described. The cube is used as an example to show how experimental data can be used to determine size. Adequate accuracy was attained with a small number of results. Use of regular or random directions was investigated. COMMON CAUSES OF CRACKS IN PM COMPACTS D.C.Zenger, H.Cai. (Husky Injection Moulding Ltd, Ontario, Canada.) Int. J. Poulder Metall., Vol 34, No 4, 1998, 3352. It is noted that, in parts made by pressing-and-sintering, most cracks arise before sintering. Prevention of cracking requires good understanding of causes and appropriate action to be taken. Causes of cracks in green compacts are assessed. It is suggested that the results may be of value to designers and engineers in establishing criteria for elimination of cracks.
Aluminium PM PRODUCTION OF HIGH STRENGTH ALUMINIUMMAGNESIUM-SCANDIUM ALLOYS R.&al, K.UKainer. (Technical-University, Clausthal-Zellerfeld, Germany.) Powder Metall., Vol41, No 2,1998,119-122. It is reported that a range of 5 Al-SC and 2 Al-Mg-Sc alloy powders, with up to Bwt%Sc, had been made by high pressure inert gas atomization. Structures and properties of the powders are described. The powders were consolidated, heat treated and structures and Maximum determined. properties Vickers hardness attained was 66. Strength increased with %Sc. Al-2%Sc had yield and tensile strengths of 238 and 325 MPa. In Al-5.5%Mg-2%Sc these were increased to 565 and 595 MPa. MECHANICAL PROPERTIES OF ALUMINIUM-CHROMIUM ALLOYS EXTRUDED FROM ATOMIZED POWDER A.Inoue et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol44, No 9, 1997, 858863. (In Japanese.) A range of Al-Cr-Ce-Co alloys, some with additions of Zr. Mn or Fe, were produced by extrusion at 250,300,350,400 or 450°C of 15 urn spherical gas atomized powders. The powders contained Al,
A&Co, and Al,,&-,. Material extruded at 300°C had Young’s modulus of 83 GPa, tensile strength of 570 MPa and 8.4% elongation.
iron and steel EFFECTS OF DENSITY AND SINTERING TEMPERATURE ON FATIGUE OF FL4405 PM HIGH STRENGTH STEEL T.Prucher et al. (Burgess-Norton Manufacturing Co, Geneva, Illinois, USA.) Powder Metall., Vol 41, No 2, 1998, 103-108. Effects of density, 7.0 and 7.4 g.cm-“, and sintering temperature, 1120 and 1315”C!, on fatigue properties of sintered FL4405 steel were investigated. Higher density steel had smaller pore size and volume and the higher sintering temperature gave more rounded pores. Fracture surfaces were macroscopically brittle with microscopic ductile dimpling. Mechanical and fatigue properties were improved at the higher density and higher sintering temperature. EFFECT OF TEMPERING TEMPERATURE ON SINTERED PROPERTIES OF SINTER HARDENED STEELS F.Chagnon, D.Barrow. (Quebec Metal Powders Ltd, Ipswich, UK.) Powder Metall., Vol41: No 2,1998, 115-117. Sinter hardening of steel was discussed with regard to process and material parameters and relationships between sintered properties and alloy compositions. Optimization of composition is shown to allow matching of properties to applications. An investigation of the effects of tempering temperature on properties of sinter hardened 2%Cu steel with 0.65 or 0.8%C is described. Samples were processed to 6.8 g.cm-3 and tempered at 150, 175 or 205°C. At 150°C there was a reduction in Vickers hardness of about 85 but an increase in tensile properties, particularly in the steel with the higher %C. DETERMINATION OF MACHINABLITY OF PM MATERIALS BY DRILLING TESTS J.R.Spirko et al. (General Carbide Corp, Johnstown, USA.) Int. J. Powder Metall., Vo134, No 3,1998,37-46. Machinability of a range of PM ferrous materials was investigated by instrumented drilling tests as functions
MPR February 1999 35
of drilling parameters and alloy composition, including machining enhancers and resin impregnation. Resin impregnation gave the greatest improvement in machinability followed by MnS. Some alloys, notably stainless steels, proved difficult to machine without impregnation. CHANGE OF DENSITY IN COLD DEFORMED SINTERED STEEL J.Lukowski, MSkura. (Slaska Polytechnic, Katowice, Poland.) Rudy Metale, Vol43, No 51998,248253. (In Polish.) An investigation to determine optimum conditions for production of defectfree sintered steel, with density increased by cold forming, is described. Choice of cold forming method is considered. DIFFUSION OF FERROUS COMPACTS DURING SINTERING K.Asaka, T.Kagaya. (Hitachi Powdered Metals Co Ltd, Matsudo, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 8,1997,751-756. (In Japanese.) Diffusion bonding in stainless steel compacts during sintering was investigated. Corrosion resistance is reduced by C so Ni and Cu were added to aid diffusion bonding. A part consisting of 304L-2%Cu and 304L sub-parts is considered to be a suitable combination of alloys. The interface is shown to be well diffused. Twins were observed in the microstructures. EFFECT OF SINTERING CONDITIONS AND ADDITION OF MOLYBDENUM ON SINTERING OF COARSE IRON POWDER S.Unami, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, No 8, 1997, 765 769. (In Japanese.) It is reported that the addition of 2 to 4wt%Mo to coarse Fe powder enhances densification during sintering. Densities of 96 to 98% were attained in solid phase sintered Fe-MO at 1300°C for 1 to 4 hours. Without MO, Fe showed little densification.
Molybdenum SINTERING OF MOLYBDENUM POWDER COMPACTS BY SPARE PLASMA SINTERING T.Sakamoto. (Yatsushiro College of Technology, Yatsushiro, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 9,1997,845-850. (In English.) Compacts of MO powder and of MO powder with Ni added as a sintering enhancer were processed by spark plasma sintering. The process is shown to be effective for MO and Mo-Ni but there
36 MPR February 1999
was excessive grain growth after longer sintering times. Mo-Ni densified more rapidly than MO. Ni reduced the activation energy for sintering.
Ceramic
.materials
CERMETS PREPARED FROM ALUMINA POWDER COATED WITH TITANIUM NITRIDE AND NICKEL S.Li et al. (Beijing University of Aeronautics and Astronautics, Beijing, China.) Znt. J. Refractory Metals Hard Mater., Vol 16, No 2, 1998119-126. A study, intended to improve A&O,Ni cermets by coating the Al,O, with TIN, is described. Powder mixtures were hot pressed to form the Al,O,ITiN-Ni cermets. Density was reduced by increase in %Al,O, and increased by finer particles. Mechanical properties were determined and were higher for the fine grained materials, 10 to 20 pm, than those of coarse grain, 40 to 50 pm. Mechanical properties, except hardness, were reduced by increase in Al,O, content. NON-SHRINKING ALUMINA MATERIALS SHarada et al. (Matsushita Electronic Components Co Ltd, Kadoma, Japan.) J. Jpn Sot. Powder Powder Metall., Vo144, No 8, 1997,729-733. (In Japanese.) A study of shaping, sintering and oxidation of Al,O,-Al materials is described. The object was to minimize shrinkage during processing. Compacts were pressed at 190 MPa and sintered in air at 1600°C. The Al oxidized above 450°C and some Al exuded from the surface of the compacts. The oxidation of Al counteracts shrinkage. MgO, CaCO, and TiO, were added to minimize loss of Al, and Si was added to oppose shrinkage above 1400°C. Sintered A&O,, with a density of 3.72 g.cmm3and 0.7% shrinkage, was produced. The structures contained mullite. FRACTURE OF ZIRCONIA THERMAL BARRIER COATINGS UNDER THERMAL FATIGUE R.Watanabe et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 8, 1997, 734739. (In Japanese.) Spalling of thermally sprayed ZrO,Y,O, coatings on a Ni-Cr-AI-Y coated stainless steel substrate was investigated during rapid thermal cycling, to simulate service conditions. Acoustic emission signals were used to detect initiation of cracks. The mechanism of spalling is discussed. The sequence is shown to be formation of cracks through the coating, then at the interface followed by detachment of the coating.
Hectrical materials
and magnetic
ENHANCEMENT OF DENSIFICATION OF IRON NITRIDE IN LIQUID PHASE SINTERING BY ADDITION OF ZINC S.Unami, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, No 8, 1997, 757764. (In Japanese.) A study of the effects of Zn on pressureless liquid phase sintering of Fe,N, to overcome the instability of Fe,N by lowering the sintering temperature, is described. Fe,N-lO%Zn powder was heat treated in H at 43O”C, mixed with a further 20%Zn powder, compacted and sintered to a density of 84%. The heat treated powder contained a FeZn phase on the Fe,N particle surfaces which was readily wetted by the additional Zn during sintering at 550°C. Fe,N has high saturation magnetization. MAGNETIC PROPERTIES OF NEODYMIUM-IRON-BORON SINTERED FROM G-TED POWDERS YKishimoto, O.Yamashita. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metal, Vo144, No 8,1997,775-780. (In Japanese.) It is reported that Nd-Fe-B magnets had been prepared from powder granulated by a spray drying technique using a polymer binder. Magnetic properties are described. CHARACTERISTICS OF FORMING BONDED MAGNET POWDERS BY ULTRASONIC VIBRATION SMino et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, NO 9, 1997,807-811. (In Japanese.) A study of the effects of oriented ultrasonic vibration on consolidation of anisotropic Nd-Fe-B magnetic powder, with an epoxy resin binder, is described. The applied vibration was shown to be sufficient to melt the binder and effects of process parameters were investigated. The technique is shown to reduce process times and temperatures.
Hard materials steels
and tool
CARBON NITRIDE J.Hofmann. (PRAMET AS, Sumperk, Czech Republic.) Pokroky Praskove Metal., Vo135, No 4,1997,5-20. (In Czech.) Recent literature concerning a new superhard material, carbon nitride, is reviewed with reference to production, properties and potential applications.
Fundamentals PARTICLE OVERLAP AND SEGREGATION PROBLEMS IN ONLINE COARSE PARTICLE SIZE MEASUREMENT C.L.Lin et al. (University of Utah, Salt Lake City, USA.) Powder Technol., Vol 98, No 1,1998, l-12. It is noted that particle overlap and segregation are factors that adversely affect the accuracy of image based particle size measurement systems. An empirical factor may be used to correct this but is of limited value. Simulation studies, using Monte Carlo methods to provide a base for image based particle size measurement systems and reliable correction factors, are described. Findings from the computer simulation were used to design a drop-box experiment. The results of the studies are shown to facilitate use of image based methods for on-line measurement of coarse particle sizes. USE OF PROJECTED AREA DISTRIBUTION FUNCTIONS IN PARTICLE SHAPE MEASUREMENT D.J.Brown, G.T.Vickers. (University of Sheffield, Sheffield, UK.) Powder Technol., Vol 98, No 3,1998,250-257. It is noted that measurement of particle shape by image analysis and light scattering depends on projected area. Non-spherical particles exhibit ranges of values for projected area and perimeter. Distribution of these variables and mean values are indicative of specific shapes. An investigation to determine
the number of results needed to give good agreement with actual distribution is described. The cube is used as an example to show how experimental data can be used to determine size. Adequate accuracy was attained with a small number of results. Use of regular or random directions was investigated. COMMON CAUSES OF CRACKS IN PM COMPACTS D.C.Zenger, H.Cai. (Husky Injection Moulding Ltd, Ontario, Canada.) Int. J. Poulder Metall., Vol 34, No 4, 1998, 3352. It is noted that, in parts made by pressing-and-sintering, most cracks arise before sintering. Prevention of cracking requires good understanding of causes and appropriate action to be taken. Causes of cracks in green compacts are assessed. It is suggested that the results may be of value to designers and engineers in establishing criteria for elimination of cracks.
Aluminium PM PRODUCTION OF HIGH STRENGTH ALUMINIUMMAGNESIUM-SCANDIUM ALLOYS R.&al, K.UKainer. (Technical-University, Clausthal-Zellerfeld, Germany.) Powder Metall., Vol41, No 2,1998,119-122. It is reported that a range of 5 Al-SC and 2 Al-Mg-Sc alloy powders, with up to Bwt%Sc, had been made by high pressure inert gas atomization. Structures and properties of the powders are described. The powders were consolidated, heat treated and structures and Maximum determined. properties Vickers hardness attained was 66. Strength increased with %Sc. Al-2%Sc had yield and tensile strengths of 238 and 325 MPa. In Al-5.5%Mg-2%Sc these were increased to 565 and 595 MPa. MECHANICAL PROPERTIES OF ALUMINIUM-CHROMIUM ALLOYS EXTRUDED FROM ATOMIZED POWDER A.Inoue et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol44, No 9, 1997, 858863. (In Japanese.) A range of Al-Cr-Ce-Co alloys, some with additions of Zr. Mn or Fe, were produced by extrusion at 250,300,350,400 or 450°C of 15 urn spherical gas atomized powders. The powders contained Al,
A&Co, and Al,,&-,. Material extruded at 300°C had Young’s modulus of 83 GPa, tensile strength of 570 MPa and 8.4% elongation.
iron and steel EFFECTS OF DENSITY AND SINTERING TEMPERATURE ON FATIGUE OF FL4405 PM HIGH STRENGTH STEEL T.Prucher et al. (Burgess-Norton Manufacturing Co, Geneva, Illinois, USA.) Powder Metall., Vol 41, No 2, 1998, 103-108. Effects of density, 7.0 and 7.4 g.cm-“, and sintering temperature, 1120 and 1315”C!, on fatigue properties of sintered FL4405 steel were investigated. Higher density steel had smaller pore size and volume and the higher sintering temperature gave more rounded pores. Fracture surfaces were macroscopically brittle with microscopic ductile dimpling. Mechanical and fatigue properties were improved at the higher density and higher sintering temperature. EFFECT OF TEMPERING TEMPERATURE ON SINTERED PROPERTIES OF SINTER HARDENED STEELS F.Chagnon, D.Barrow. (Quebec Metal Powders Ltd, Ipswich, UK.) Powder Metall., Vol41: No 2,1998, 115-117. Sinter hardening of steel was discussed with regard to process and material parameters and relationships between sintered properties and alloy compositions. Optimization of composition is shown to allow matching of properties to applications. An investigation of the effects of tempering temperature on properties of sinter hardened 2%Cu steel with 0.65 or 0.8%C is described. Samples were processed to 6.8 g.cm-3 and tempered at 150, 175 or 205°C. At 150°C there was a reduction in Vickers hardness of about 85 but an increase in tensile properties, particularly in the steel with the higher %C. DETERMINATION OF MACHINABLITY OF PM MATERIALS BY DRILLING TESTS J.R.Spirko et al. (General Carbide Corp, Johnstown, USA.) Int. J. Powder Metall., Vo134, No 3,1998,37-46. Machinability of a range of PM ferrous materials was investigated by instrumented drilling tests as functions
MPR February 1999 35
of drilling parameters and alloy composition, including machining enhancers and resin impregnation. Resin impregnation gave the greatest improvement in machinability followed by MnS. Some alloys, notably stainless steels, proved difficult to machine without impregnation. CHANGE OF DENSITY IN COLD DEFORMED SINTERED STEEL J.Lukowski, MSkura. (Slaska Polytechnic, Katowice, Poland.) Rudy Metale, Vol43, No 51998,248253. (In Polish.) An investigation to determine optimum conditions for production of defectfree sintered steel, with density increased by cold forming, is described. Choice of cold forming method is considered. DIFFUSION OF FERROUS COMPACTS DURING SINTERING K.Asaka, T.Kagaya. (Hitachi Powdered Metals Co Ltd, Matsudo, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 8,1997,751-756. (In Japanese.) Diffusion bonding in stainless steel compacts during sintering was investigated. Corrosion resistance is reduced by C so Ni and Cu were added to aid diffusion bonding. A part consisting of 304L-2%Cu and 304L sub-parts is considered to be a suitable combination of alloys. The interface is shown to be well diffused. Twins were observed in the microstructures. EFFECT OF SINTERING CONDITIONS AND ADDITION OF MOLYBDENUM ON SINTERING OF COARSE IRON POWDER S.Unami, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, No 8, 1997, 765 769. (In Japanese.) It is reported that the addition of 2 to 4wt%Mo to coarse Fe powder enhances densification during sintering. Densities of 96 to 98% were attained in solid phase sintered Fe-MO at 1300°C for 1 to 4 hours. Without MO, Fe showed little densification.
Molybdenum SINTERING OF MOLYBDENUM POWDER COMPACTS BY SPARE PLASMA SINTERING T.Sakamoto. (Yatsushiro College of Technology, Yatsushiro, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 9,1997,845-850. (In English.) Compacts of MO powder and of MO powder with Ni added as a sintering enhancer were processed by spark plasma sintering. The process is shown to be effective for MO and Mo-Ni but there
36 MPR February 1999
was excessive grain growth after longer sintering times. Mo-Ni densified more rapidly than MO. Ni reduced the activation energy for sintering.
Ceramic
.materials
CERMETS PREPARED FROM ALUMINA POWDER COATED WITH TITANIUM NITRIDE AND NICKEL S.Li et al. (Beijing University of Aeronautics and Astronautics, Beijing, China.) Znt. J. Refractory Metals Hard Mater., Vol 16, No 2, 1998119-126. A study, intended to improve A&O,Ni cermets by coating the Al,O, with TIN, is described. Powder mixtures were hot pressed to form the Al,O,ITiN-Ni cermets. Density was reduced by increase in %Al,O, and increased by finer particles. Mechanical properties were determined and were higher for the fine grained materials, 10 to 20 pm, than those of coarse grain, 40 to 50 pm. Mechanical properties, except hardness, were reduced by increase in Al,O, content. NON-SHRINKING ALUMINA MATERIALS SHarada et al. (Matsushita Electronic Components Co Ltd, Kadoma, Japan.) J. Jpn Sot. Powder Powder Metall., Vo144, No 8, 1997,729-733. (In Japanese.) A study of shaping, sintering and oxidation of Al,O,-Al materials is described. The object was to minimize shrinkage during processing. Compacts were pressed at 190 MPa and sintered in air at 1600°C. The Al oxidized above 450°C and some Al exuded from the surface of the compacts. The oxidation of Al counteracts shrinkage. MgO, CaCO, and TiO, were added to minimize loss of Al, and Si was added to oppose shrinkage above 1400°C. Sintered A&O,, with a density of 3.72 g.cmm3and 0.7% shrinkage, was produced. The structures contained mullite. FRACTURE OF ZIRCONIA THERMAL BARRIER COATINGS UNDER THERMAL FATIGUE R.Watanabe et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metal, Vol 44, No 8, 1997, 734739. (In Japanese.) Spalling of thermally sprayed ZrO,Y,O, coatings on a Ni-Cr-AI-Y coated stainless steel substrate was investigated during rapid thermal cycling, to simulate service conditions. Acoustic emission signals were used to detect initiation of cracks. The mechanism of spalling is discussed. The sequence is shown to be formation of cracks through the coating, then at the interface followed by detachment of the coating.
Hectrical materials
and magnetic
ENHANCEMENT OF DENSIFICATION OF IRON NITRIDE IN LIQUID PHASE SINTERING BY ADDITION OF ZINC S.Unami, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, No 8, 1997, 757764. (In Japanese.) A study of the effects of Zn on pressureless liquid phase sintering of Fe,N, to overcome the instability of Fe,N by lowering the sintering temperature, is described. Fe,N-lO%Zn powder was heat treated in H at 43O”C, mixed with a further 20%Zn powder, compacted and sintered to a density of 84%. The heat treated powder contained a FeZn phase on the Fe,N particle surfaces which was readily wetted by the additional Zn during sintering at 550°C. Fe,N has high saturation magnetization. MAGNETIC PROPERTIES OF NEODYMIUM-IRON-BORON SINTERED FROM G-TED POWDERS YKishimoto, O.Yamashita. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metal, Vo144, No 8,1997,775-780. (In Japanese.) It is reported that Nd-Fe-B magnets had been prepared from powder granulated by a spray drying technique using a polymer binder. Magnetic properties are described. CHARACTERISTICS OF FORMING BONDED MAGNET POWDERS BY ULTRASONIC VIBRATION SMino et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 44, NO 9, 1997,807-811. (In Japanese.) A study of the effects of oriented ultrasonic vibration on consolidation of anisotropic Nd-Fe-B magnetic powder, with an epoxy resin binder, is described. The applied vibration was shown to be sufficient to melt the binder and effects of process parameters were investigated. The technique is shown to reduce process times and temperatures.
Hard materials steels
and tool
CARBON NITRIDE J.Hofmann. (PRAMET AS, Sumperk, Czech Republic.) Pokroky Praskove Metal., Vo135, No 4,1997,5-20. (In Czech.) Recent literature concerning a new superhard material, carbon nitride, is reviewed with reference to production, properties and potential applications.