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Methods for grain size measurement in tungsten carbide powders and hardmetals
powders. Process conditions were outlined. Flake with a thickness:diameter ratio of 1:lOOO could be attained. Relationships between starting powder characteristics and finished flake were investigated experimentally and by modelling for a range of metals. Flake materials were characterized by scanning electron microscopy. MICROSTRUCTURE AND MECHANICAL PROPERTIES NICKEL-ALUMINIUM-SILICON CARBIDE WHISKER
OF
S.J.Hwang, D.J.Kang. (Daejin University, Korea.) It was reported that Ni aluminide materials, reinforced with Sic whisker, had been prepared by ball milling prealloyed Ni-Al powder and characterized to study the evolution of the alloying process. Powders were hot consolidated by a range of methods. Consolidated samples were characterized for structures and mechanical property relationships using hot compression tests up to 1125 “C. The materials were shown to have potential for high temperature structural applications. SYNTHESIS OF NANO-CRYSTALLINE TITANIUM CARBIDE AND DISPERSION IN AN IRON-ALUMINIUM MATRIX
F.H.Froes et al. (University of Idaho, USA.) Methods of preparing micro-crystalline metal carbides, by comminution of carbides or by synthesis from precursors, were outlined. The need to make these in commercial quantities was noted. It was reported that TIC had been synthesized by reaction between TiCl,, CaC, and Mg, induced by mechanical alloying at ambient temperatures. CaCl, and MgCl, were leached out leaving TIC powder, with high purity and a particle size range of 10 to 300 nm. MA was also used to disperse the TiC in Fe-Al powder, which was then consolidated by a press-and-sinter route. TiC was shown to be uniformly dispersed in the matrix.
Machinability materials
of PM
costs. The behaviour of green parts during machining (drilling) was described. Machinability indices were correlated with characteristics of drilled holes. Key factors for satisfactory machining were discussed.
established methods. It was noted that specimen preparation is important for valid measurements to be obtained.
EVALUATION OF MACHINABILITY EFFECTS OF STEEL PROPERTIES SHAPE OF DRILLING CURVES
K.Rodiger et al. (Widia GmbH, Essen, Germany.) The need for cost reductions in production of hardmetals was noted and the importance of moulding and shaping was emphasized. Near net shaping, by die pressing and injection moulding, was discussed with respect to powder and process parameters including different types of press, granulation of powder, shrinkage, lowering of press forces and computer simulation of pressing and sintering.
ON
C.Blais et al. (Domfer Metal Powders Ltd, Canada.) It was noted that even though PM parts can be produced to near net-shape some finish machining operations may be needed, that the machinability of PM materials may be inferior to wrought materials, due to effects of pores and hard particles, and that machinability is difficult to quantify. Drilling tests are often used to evaluate machinability but may be difficult to interpret. Correlations between drilling tests and properties of PM materials were discussed. EURO PM’99. The following Abstracts are from papers presented at the European Conference on Advances in Hard Materials Production and International Workshop on Diamond Tool Production, which were held in Turin, Italy, in November 1999.
Hard materials PRODUCTION AND APPLICATIONS OF ADVANCED GRADES OF TUNGSTEN CARBIDE AND BINDER POWDERS
B.Mende et al. (H.C.Starck GmbH, Goslar, Germany.) Properties and applications of new hardmetal powders were described with particular regard to ultrafine WC and fine grain and highly sinteractive Co-NiFe. The characteristics of these are said to be significant in attaining high performance in sintered carbides and diamond tools. Correlations were given between powder and hardmetal properties and structures, which were shown to be important for optimized sintering, structural evolution and improved properties of the tool materials.
CHARACTERIZING MACHINABILITY OF GREEN PM PARTS
METHODS FOR GRAIN SIZE MEASUREMENT IN TUNGSTEN CARBIDE POWDERS AND HARDMETALS
M.Gagne, F.Chagnon. (Quebec Metal Powders Ltd, Quebec, Canada.) Machining of PM materials was reviewed with respect to costs, additions, such as MnS or BN, to enhance machinability and the possibility of machining in the green state to reduce
B.Roebuck et al. (National Physical Laboratory, Teddington, UK.) The trend towards finer grades of hardmetals and difficulties in measurement of fine grain sizes were discussed. New techniques for size characterization were reviewed and compared with
48
MPR October 2000
NEAR NET SHAPING HARDMETALS
HOT MOULDING AND CERAMICS
FOR
OF HARDMETALS
R.Lenk et al. (Fraunhofer Gesellschaft IKTS, Dresden, Germany.) The advantages of hot moulding for production of parts from powder were discussed, for example lower energy costs and less tool wear. Hot moulding was shown to allow production of complex shaped parts and good part dimensional accuracy, reducing the need for finishing operations, to be attained. Some examples of hardmetal and ceramic parts were presented. GRAIN GROWTH CONTROL IN MICROWAVE SINTERING OF ULTBAFINE TUNGSTEN CARBIDECOBALT
D.Agrawal et al. (Pennsylvania State University, USA.) Use of ultrafine grades of WC-Co to meet demands for increased performance was discussed. It was noted that there is a consequent need to minimize grain growth during sintering. Microwave sintering, which is rapid and avoids the need for post sintering treatment, was explored, to study grain growth and microstructures. Comparison was made with conventionally sintered materials and effects of growth inhibitors. PROPERTIES OF ULTRAFINE GRAIN CEMENTED CARBIDES MADE BY A NEW SINTERING PROCESS
H.Moriguchi et al. (Sumitomo Electric Industries, Itami, Japan.) Ultrafine, 0.25 ,um, WC-12%Co0.4%VC was prepared by wet mixing and drying, pressurization and pulse current sintering. Comparison was made with conventionally produced materials. Material made by the new
OF
S.J.Hwang, D.J.Kang. (Daejin University, Korea.) It was reported that Ni aluminide materials, reinforced with Sic whisker, had been prepared by ball milling prealloyed Ni-Al powder and characterized to study the evolution of the alloying process. Powders were hot consolidated by a range of methods. Consolidated samples were characterized for structures and mechanical property relationships using hot compression tests up to 1125 “C. The materials were shown to have potential for high temperature structural applications. SYNTHESIS OF NANO-CRYSTALLINE TITANIUM CARBIDE AND DISPERSION IN AN IRON-ALUMINIUM MATRIX
F.H.Froes et al. (University of Idaho, USA.) Methods of preparing micro-crystalline metal carbides, by comminution of carbides or by synthesis from precursors, were outlined. The need to make these in commercial quantities was noted. It was reported that TIC had been synthesized by reaction between TiCl,, CaC, and Mg, induced by mechanical alloying at ambient temperatures. CaCl, and MgCl, were leached out leaving TIC powder, with high purity and a particle size range of 10 to 300 nm. MA was also used to disperse the TiC in Fe-Al powder, which was then consolidated by a press-and-sinter route. TiC was shown to be uniformly dispersed in the matrix.
Machinability materials
of PM
costs. The behaviour of green parts during machining (drilling) was described. Machinability indices were correlated with characteristics of drilled holes. Key factors for satisfactory machining were discussed.
established methods. It was noted that specimen preparation is important for valid measurements to be obtained.
EVALUATION OF MACHINABILITY EFFECTS OF STEEL PROPERTIES SHAPE OF DRILLING CURVES
K.Rodiger et al. (Widia GmbH, Essen, Germany.) The need for cost reductions in production of hardmetals was noted and the importance of moulding and shaping was emphasized. Near net shaping, by die pressing and injection moulding, was discussed with respect to powder and process parameters including different types of press, granulation of powder, shrinkage, lowering of press forces and computer simulation of pressing and sintering.
ON
C.Blais et al. (Domfer Metal Powders Ltd, Canada.) It was noted that even though PM parts can be produced to near net-shape some finish machining operations may be needed, that the machinability of PM materials may be inferior to wrought materials, due to effects of pores and hard particles, and that machinability is difficult to quantify. Drilling tests are often used to evaluate machinability but may be difficult to interpret. Correlations between drilling tests and properties of PM materials were discussed. EURO PM’99. The following Abstracts are from papers presented at the European Conference on Advances in Hard Materials Production and International Workshop on Diamond Tool Production, which were held in Turin, Italy, in November 1999.
Hard materials PRODUCTION AND APPLICATIONS OF ADVANCED GRADES OF TUNGSTEN CARBIDE AND BINDER POWDERS
B.Mende et al. (H.C.Starck GmbH, Goslar, Germany.) Properties and applications of new hardmetal powders were described with particular regard to ultrafine WC and fine grain and highly sinteractive Co-NiFe. The characteristics of these are said to be significant in attaining high performance in sintered carbides and diamond tools. Correlations were given between powder and hardmetal properties and structures, which were shown to be important for optimized sintering, structural evolution and improved properties of the tool materials.
CHARACTERIZING MACHINABILITY OF GREEN PM PARTS
METHODS FOR GRAIN SIZE MEASUREMENT IN TUNGSTEN CARBIDE POWDERS AND HARDMETALS
M.Gagne, F.Chagnon. (Quebec Metal Powders Ltd, Quebec, Canada.) Machining of PM materials was reviewed with respect to costs, additions, such as MnS or BN, to enhance machinability and the possibility of machining in the green state to reduce
B.Roebuck et al. (National Physical Laboratory, Teddington, UK.) The trend towards finer grades of hardmetals and difficulties in measurement of fine grain sizes were discussed. New techniques for size characterization were reviewed and compared with
48
MPR October 2000
NEAR NET SHAPING HARDMETALS
HOT MOULDING AND CERAMICS
FOR
OF HARDMETALS
R.Lenk et al. (Fraunhofer Gesellschaft IKTS, Dresden, Germany.) The advantages of hot moulding for production of parts from powder were discussed, for example lower energy costs and less tool wear. Hot moulding was shown to allow production of complex shaped parts and good part dimensional accuracy, reducing the need for finishing operations, to be attained. Some examples of hardmetal and ceramic parts were presented. GRAIN GROWTH CONTROL IN MICROWAVE SINTERING OF ULTBAFINE TUNGSTEN CARBIDECOBALT
D.Agrawal et al. (Pennsylvania State University, USA.) Use of ultrafine grades of WC-Co to meet demands for increased performance was discussed. It was noted that there is a consequent need to minimize grain growth during sintering. Microwave sintering, which is rapid and avoids the need for post sintering treatment, was explored, to study grain growth and microstructures. Comparison was made with conventionally sintered materials and effects of growth inhibitors. PROPERTIES OF ULTRAFINE GRAIN CEMENTED CARBIDES MADE BY A NEW SINTERING PROCESS
H.Moriguchi et al. (Sumitomo Electric Industries, Itami, Japan.) Ultrafine, 0.25 ,um, WC-12%Co0.4%VC was prepared by wet mixing and drying, pressurization and pulse current sintering. Comparison was made with conventionally produced materials. Material made by the new