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Developments in vacuum and overpressure sintering
Hard materials and tools steels
DENSIFICATION OF TUNGSTEN CARBIDE-TITANIUM CARBIDE WITH NICKEL BINDER
OXIDATION OF TUNGSTEN CARBIDE CERMETS AT 600” TO 800°C
WK. Park et al. (Inha University, Inchon, Korea.) J. Korean Inst. of Metals, Vol 34, No 2, 1996, 270-278. (In Korean.) Studies of WC-Ni cermets with additions of TiC and Sic are described. The (W,Ti,Si)C-lOwt%Ni materials were produced from W and ‘DC powders mixed with SiOz and C, heated at 1500 to 1550°C to carburize mixed with Ni, pressed and sintered. The grain size was 0.4 to 1.0 pm and Vicker’s hardness was 1830 at 97% density. Ti is considered to inhibit grain growth and to enhance hardness by formation of (W,Ti)C and NisTi which was confirmed by microscopy.
E.I. Golovko et al. (Academy of Sciences of the Ukraine, Kiev, Ukraine.) Int. J. Refractory Metals and Hard Materials, Vol 14, No 4, 1996, 289-295. Oxidation of WC with 16%Co, 16XNi or 8%Ni-8%Co at 500 to 800°C was investigated with due regard to the energetics of oxidation. The Co alloy oxidized less than the Ni alloy at 650 to 800°C. The results are discussed in terms of phase composition, formation of scales and protective properties of oxides COO, NiO, WOs and complex oxides based on (Ni,Co) WO1.
Intermetallic
materials
WEAR AND FAILURE OF TITANIUM NITRIDE COATED HIGH SPEED STEELS AND CEMENTED CARBIDES
MICROSTRUCTURAL CONTROL IN TITANIUM ALUMINIDE BY MECHANICAL ALLOYING AND HIP
H. Hnninen et al. (Helsinki University of Technology, Helsinki, Finland.) Metallurgical Trans. A, Vol 27A No 9, 1996, 27962808. Wear, fatigue, fracture and tool life of PM high speed steel and cemented carbides, both coated with TIN were investigated during machining. PM 316L and duplex 2205 stainless steels were used. It is reported that at high cutting speeds fatigue induced failure and diffusion wear affected life of TiN coated cemented carbide tools. At low cutting speed tool life of coated HSS was longer when cutting 2205 steel. Coated cemented carbides had longer life when cutting 316L at high speeds.
F.H. Frees et al. (University of Idaho, Moscow, Idaho, USA) J. Metals, Vol 48, No 7, 1996, 40-41. m alloys are discussed. A method for control of grain size by use of mechanical alloying and hot isostatic pressing is described.
FRACTURE BEIIAVIOUR OF COBALT CEMENTED TUNGSTEN CARBIDE L. Jinyao, H. Ping. (Central South University of Technology, Hunan, China.) PM Technology, Vol 14, No 2, 1996, 83-87. (In Chinese.) Microstructural inspection of WC-Co is described use being made of optical and electron techniques. Structural observations are correlated with fracture characteristics. Structural factors affecting fracture strength are discussed. EFFECTS OF SMALL AMOUNTS OF ALUMINIUM ON STRUCTURE AND PROPERTIES OF CEMENTED CARBIDE H. Shi et al. (University of Science and Technology, Beijing, China.) PM Technol063: Vol 14, No 2, 1996, 108-115. (In Chinese.) The effects of small concentrations of Al on structure and properties of WC- 13% (FeCo-Ni) cemented carbids were investigated. The Al is reported to refine the WC grains and to increase hardness and bend strength. The binder phase is shown to be y phase with lath martensite, a little uFe and carbides other than WC.
MATHEMATICAL MODELLING OF COMBUSTION SYNTHESIS OF MAGNESIUM NICKELIDE J. Yagi et al. (Tohoku University, Sendai, Japan.) J. Japan Inst. of Metals, Vol 60, No 7, 1996, 647-652. (In Japanese.) Mathematical modelling of combustion synthesis of MgzNi is discussed with reference to the need for experimental verification. Experiments using laser flash and differential scanning calorimetry are described. The model is described and the experimental results are shown to agree well enough to confirm the model. Synthesis mechanisms are described. PROPERTIES OF ALIJMINIUMTITANIUM-NITROGEN ALLOY PREPARED BY REACTION SINTERING
Warsaw, Poland.) Metal. h-oszkow, Vol 29, No 1, 1996, 3-11. (In Polish.) Methods of debinding are discussed and results of studies of 316L, stainless steel, carbonyl Fe and cemented carbides, with paraffin wax or polyethylene oxide based binders are presented. A two step solvent and thermal debinding process was used. Results are expressed graphically and supported by scanning electron micrographs. PM
components
SHOT FORGING OF A PM CONNECTING ROD - A THREEDIMENSIONAL COMPUTER MODEL AGK. Jinka, M. Bellet. (Ecole Superieure des Mines de Paris, Antipolis, France.) Int. J. Powder Metallurgy, Vol 32, No 3, 1996, 255-258. A simulation of hot forging of a PM automotive connecting rod is described. The results are discussed in terms of material density as a function of temperature.
Processing CHEMICAL AND ELECTRICAL INSULATION OF FINE IRON AND COBALT PARTICLES A. Garreau, PLatare. (CEA, France.) Phosphate coating of fine Fe and Co powders was discussed with regard to chemical and electrical effects. It was reported that phosphate coating increases oxidation resistance up to 400°C but thermal treatment is required to stabilize the coating. The possibility of mixing the metal powder with a binder without any chemical interaction was noted and choice of stable binder was reviewed.
M. Morlshita et al. (Himeji University of Technology, Himeji, Japan.) J. Japan SOC. Powder and Powder Metallurgv, Vol 42, No 3, 1995, 408-412. (In Japanese.) It is reported that the addition of Ni to reaction sintered Al-Ti-N alloy had resulted in increased bend strength and ductility. The structure of the alloy is shown to be TiAls and AlN. The increased properties are attributed to a change in the structure of TiAls h-om DOzz to Llz.
HMZ SPECLAL SERVICE RECYCLING
Metal injection moulding
D. Ermel. (ALD Vacuum Technologies GmbH, Germany.) Improvements in furnace design, contol systems, furnace temperature uniformity, costs and capacity were reviewed in respect of hardmetal and other PM parts. Processes
INVESTIGATIONS OF BINDER REMOVAL IN METAL INJECTION MOULDING D. Bialo, T. Kulesza. (Polytechnic of Warsaw,
C. Stambolidis. (HMZ as, Czech Republic.) It was reported that work on recycling W scrap into WC and W powders is in progress. Process steps were summarized as roasting, wet processing, reduction and carburizing. DEVELOPMENTS IN VACUUM AND OVERPRESSURE SINTERING
MPR February 1997 37
and applications for dewaxing, vacuum and overpressure sintering were described. PREPARATION OF TITANIUM CARBIDE-CHROMIUM ALLOYED-IRON CERMETS BY REACTUVE HOT PRESSING V. Potapenko, MSKovaltchenko. (Academy of Sciences of Ukraine, Kiev, Ukraine.) It was reported that Tic-Fe cermets are formed during hot pressing of ferrochromium, C and Fe at 1085 to 1200°C. Cr powder additions do not alloy with the Fe binder and Cr should be added as carbide. CraCz and free C react in the melt and the exothermic process requires a lower temperature giving stoichiometric TX in a Cr alloyed Fe binder. HARDMETAL PARTS BY INJECTION MOULDING USING A POLYACETYL BASED BINDER SYSTEM W. Hesse, P. Trubenbach. (BASF AG, Germany.) Use of injection moulding for hardmetal parts was discussed with note taken of process problems, particularly, segregation due to high density of WC and undesirable chemical reactions during debinding. Catalytic debinding of polyacetyl binders using oxalic acid as the catalyst was considered. Properties of hardmetal feedstocks and process conditions were discussed and examples of IM parts were presented. NUMERICAL SIMULATION OF COMPACTION AND SINTERING OF CEMENTED CARBIDE D. Bouvardet et al. (Inst. National Polytechnique, Grenoble, France.) Shape changes during sintering were discussed with regard to green density gradients and consequent heterogeneous streses. Simulation of pressing and sintering was shown to allow prediction of final shape. Simulation of processing a WCCo part was discussed. Compaction was described by equations, parameters being estimated by experiment. A linear viscous model was used for sintering. Predictions were compared with experiment. MICROWAVE SINTERING OF IL4RDMETALS AND CERAMICS M. WillertPorada et al. (University of Dortmund, Dortmund, Germany.) Application of microwaves to sintering was discussed with reference to properties of hardmetals, new materials and researches on ceramics. Principles of interactions between microwaves and hardmetals and ceramics were outlined. Results on AlzOa, Al,Oa-TX and WC-Co were presented. Mechanical properties of WC-Co were given. The potential of microwave heating, for sintering, was reviewed. 38
MPR February
1997
MACROSCOPIC AND MICROSTRUCTURAL EVOLUTION IN TUNGSTEN CARBIDE IN SOLID STATE SINTERING J.M. Missiaen. (Laboratoire de Thermodynique et Physico-Chimie Metalluriques, France.) An investigation of structural evolution during solid state sintering of WC-Co, using various techniques, was described. Measurements of phases were made. Features of the sintering were characterized. The objective was to relate structure and shrinkage. DENSIFICATION DURING SINTERING OF TUNGSTEN CARBIDE-COBALT S. Haglund et al. (Royal Inst. of Technology, Stockholm, Sweden.) Densification of WC-Co in the solid state was discussed and it was noted that this can account for up to 75% of the total sintering densiEcation. Dilatometry, with and without a small, 1 MPa, load, was used to study solid state sintering. The results were discussed, mechanisms identified and a model was proposed. Use of the model in other systems was considered. INJECTION MOULDING OF TUNGSTEN CARBIDE-COBALT USING TWO BINDER SYSTEMS M. Youseffi, I.A. Menzies. (University of Loughborough, Loughborough, UK) A study of injection moulding of WCGwt%Co was described. Two binder systems were used. One was based on waxes. The other was water soluble polyvinyl alcohol based. Optimum feedstock compositions were formulated and rheological properties investigated. A high solids loading of 65% was reported with high densities attained.
Properties
and testing
SINTERING AND PROPERTIES OF TUNGSTEN CARBIDE-COBALT RELATED TO POWDER PROPERTIES B. Roebuck et al. (National Physical La boratory, Teddington, Middlesex, UK) A study of sintering of WC-Co, with a wide range of grain sizes, was described. Sintering, structure and properties were correlated with powder characteristics. HARDMETALS AND THERMODYNAMIC MODELLING B. Uhrenius. (Sandvik Hardmetals, Sweden.) Computer programs and databases were discussed with regard to calculation of alloy thermodynamics, phase equilibria and development of new alloy grades. In respect of cemented carbides these tools are used to describe relationships between process conditions and structure. Processing can be described mathematically
by use of computer programs. Applications to WC-Co and multi-component systems were outlined. FINE GRAINED TUNGSTEN CARBIDEVANADIUM CARBIDE-COBALT HARDMETAL D. Whitefield et al. (University of the Witwatersrand, South Africa.) Preparation of WC-12wt”%VC-lO%Cowas described. The mean particle sizes were, WC, less than 1 urn and VC, about 2 pm. Properties of the material were presented. Vicker’s hardness at 1700 is higher than WC-6%Co and the toughness is also higher. INFLUENCE OF GRAIN SIZE ON HARDNESS AND TOUGHNESS OF TUNGSTEN CARBIDE-COBALT Y. Milman et al. (Academy of Sciences of the Ukraine, Kiev, Ukraine.) Hardness and fracture toughness of WCCo were investigated in the range -196 to 900°C as a function of WC grain size. A HallPetch type of relationship was found. Thermal softening was reported to decrease with decrease in WC grain size. EFFECT OF POROSITY ON TRANSVERSE RUPTURE AND FRACTURE TOUGHNESS OF A TWO PHASE ALLOY A. Laptev. (Academy of Sciences of the Ukraine, Kiev, Ukraine.) It was reported that at some value of relative porosity fracture toughness and yield strength of plastic materials are increased. Effect of porosity of brittle materials was discussed with regard to pore size. A study of the effects of porosity on transverse rupture strength and fracture toughness of a hard metal with 24% of a plastic phase was described. Variation in porosity was attained by variation of hot pressing conditions. TESTING AND GRAIN SIZE OF TUNGSTEN CARBIDE POWDERS - POST SINTERING CHARACTERIZATION P. Klapetek, J. Spacil. (Pramet as., Czech Republic.) An investigation of WC-lO%Co hardmetals, made from differing grades of WC, was described. A milling test was proposed and parameters requiring control were identified.
Coatings and ultrahard materials CHEMICALLY VAPOUR DEPOSITED DIAMOND CUTTING TOOL APPLICATIONS IN COMPOSITE MATERIALS R. Hay. (Norton Diamond Film Co., USA) CVD diamond cutting tools were reviewed. It was reported that thick and
DENSIFICATION OF TUNGSTEN CARBIDE-TITANIUM CARBIDE WITH NICKEL BINDER
OXIDATION OF TUNGSTEN CARBIDE CERMETS AT 600” TO 800°C
WK. Park et al. (Inha University, Inchon, Korea.) J. Korean Inst. of Metals, Vol 34, No 2, 1996, 270-278. (In Korean.) Studies of WC-Ni cermets with additions of TiC and Sic are described. The (W,Ti,Si)C-lOwt%Ni materials were produced from W and ‘DC powders mixed with SiOz and C, heated at 1500 to 1550°C to carburize mixed with Ni, pressed and sintered. The grain size was 0.4 to 1.0 pm and Vicker’s hardness was 1830 at 97% density. Ti is considered to inhibit grain growth and to enhance hardness by formation of (W,Ti)C and NisTi which was confirmed by microscopy.
E.I. Golovko et al. (Academy of Sciences of the Ukraine, Kiev, Ukraine.) Int. J. Refractory Metals and Hard Materials, Vol 14, No 4, 1996, 289-295. Oxidation of WC with 16%Co, 16XNi or 8%Ni-8%Co at 500 to 800°C was investigated with due regard to the energetics of oxidation. The Co alloy oxidized less than the Ni alloy at 650 to 800°C. The results are discussed in terms of phase composition, formation of scales and protective properties of oxides COO, NiO, WOs and complex oxides based on (Ni,Co) WO1.
Intermetallic
materials
WEAR AND FAILURE OF TITANIUM NITRIDE COATED HIGH SPEED STEELS AND CEMENTED CARBIDES
MICROSTRUCTURAL CONTROL IN TITANIUM ALUMINIDE BY MECHANICAL ALLOYING AND HIP
H. Hnninen et al. (Helsinki University of Technology, Helsinki, Finland.) Metallurgical Trans. A, Vol 27A No 9, 1996, 27962808. Wear, fatigue, fracture and tool life of PM high speed steel and cemented carbides, both coated with TIN were investigated during machining. PM 316L and duplex 2205 stainless steels were used. It is reported that at high cutting speeds fatigue induced failure and diffusion wear affected life of TiN coated cemented carbide tools. At low cutting speed tool life of coated HSS was longer when cutting 2205 steel. Coated cemented carbides had longer life when cutting 316L at high speeds.
F.H. Frees et al. (University of Idaho, Moscow, Idaho, USA) J. Metals, Vol 48, No 7, 1996, 40-41. m alloys are discussed. A method for control of grain size by use of mechanical alloying and hot isostatic pressing is described.
FRACTURE BEIIAVIOUR OF COBALT CEMENTED TUNGSTEN CARBIDE L. Jinyao, H. Ping. (Central South University of Technology, Hunan, China.) PM Technology, Vol 14, No 2, 1996, 83-87. (In Chinese.) Microstructural inspection of WC-Co is described use being made of optical and electron techniques. Structural observations are correlated with fracture characteristics. Structural factors affecting fracture strength are discussed. EFFECTS OF SMALL AMOUNTS OF ALUMINIUM ON STRUCTURE AND PROPERTIES OF CEMENTED CARBIDE H. Shi et al. (University of Science and Technology, Beijing, China.) PM Technol063: Vol 14, No 2, 1996, 108-115. (In Chinese.) The effects of small concentrations of Al on structure and properties of WC- 13% (FeCo-Ni) cemented carbids were investigated. The Al is reported to refine the WC grains and to increase hardness and bend strength. The binder phase is shown to be y phase with lath martensite, a little uFe and carbides other than WC.
MATHEMATICAL MODELLING OF COMBUSTION SYNTHESIS OF MAGNESIUM NICKELIDE J. Yagi et al. (Tohoku University, Sendai, Japan.) J. Japan Inst. of Metals, Vol 60, No 7, 1996, 647-652. (In Japanese.) Mathematical modelling of combustion synthesis of MgzNi is discussed with reference to the need for experimental verification. Experiments using laser flash and differential scanning calorimetry are described. The model is described and the experimental results are shown to agree well enough to confirm the model. Synthesis mechanisms are described. PROPERTIES OF ALIJMINIUMTITANIUM-NITROGEN ALLOY PREPARED BY REACTION SINTERING
Warsaw, Poland.) Metal. h-oszkow, Vol 29, No 1, 1996, 3-11. (In Polish.) Methods of debinding are discussed and results of studies of 316L, stainless steel, carbonyl Fe and cemented carbides, with paraffin wax or polyethylene oxide based binders are presented. A two step solvent and thermal debinding process was used. Results are expressed graphically and supported by scanning electron micrographs. PM
components
SHOT FORGING OF A PM CONNECTING ROD - A THREEDIMENSIONAL COMPUTER MODEL AGK. Jinka, M. Bellet. (Ecole Superieure des Mines de Paris, Antipolis, France.) Int. J. Powder Metallurgy, Vol 32, No 3, 1996, 255-258. A simulation of hot forging of a PM automotive connecting rod is described. The results are discussed in terms of material density as a function of temperature.
Processing CHEMICAL AND ELECTRICAL INSULATION OF FINE IRON AND COBALT PARTICLES A. Garreau, PLatare. (CEA, France.) Phosphate coating of fine Fe and Co powders was discussed with regard to chemical and electrical effects. It was reported that phosphate coating increases oxidation resistance up to 400°C but thermal treatment is required to stabilize the coating. The possibility of mixing the metal powder with a binder without any chemical interaction was noted and choice of stable binder was reviewed.
M. Morlshita et al. (Himeji University of Technology, Himeji, Japan.) J. Japan SOC. Powder and Powder Metallurgv, Vol 42, No 3, 1995, 408-412. (In Japanese.) It is reported that the addition of Ni to reaction sintered Al-Ti-N alloy had resulted in increased bend strength and ductility. The structure of the alloy is shown to be TiAls and AlN. The increased properties are attributed to a change in the structure of TiAls h-om DOzz to Llz.
HMZ SPECLAL SERVICE RECYCLING
Metal injection moulding
D. Ermel. (ALD Vacuum Technologies GmbH, Germany.) Improvements in furnace design, contol systems, furnace temperature uniformity, costs and capacity were reviewed in respect of hardmetal and other PM parts. Processes
INVESTIGATIONS OF BINDER REMOVAL IN METAL INJECTION MOULDING D. Bialo, T. Kulesza. (Polytechnic of Warsaw,
C. Stambolidis. (HMZ as, Czech Republic.) It was reported that work on recycling W scrap into WC and W powders is in progress. Process steps were summarized as roasting, wet processing, reduction and carburizing. DEVELOPMENTS IN VACUUM AND OVERPRESSURE SINTERING
MPR February 1997 37
and applications for dewaxing, vacuum and overpressure sintering were described. PREPARATION OF TITANIUM CARBIDE-CHROMIUM ALLOYED-IRON CERMETS BY REACTUVE HOT PRESSING V. Potapenko, MSKovaltchenko. (Academy of Sciences of Ukraine, Kiev, Ukraine.) It was reported that Tic-Fe cermets are formed during hot pressing of ferrochromium, C and Fe at 1085 to 1200°C. Cr powder additions do not alloy with the Fe binder and Cr should be added as carbide. CraCz and free C react in the melt and the exothermic process requires a lower temperature giving stoichiometric TX in a Cr alloyed Fe binder. HARDMETAL PARTS BY INJECTION MOULDING USING A POLYACETYL BASED BINDER SYSTEM W. Hesse, P. Trubenbach. (BASF AG, Germany.) Use of injection moulding for hardmetal parts was discussed with note taken of process problems, particularly, segregation due to high density of WC and undesirable chemical reactions during debinding. Catalytic debinding of polyacetyl binders using oxalic acid as the catalyst was considered. Properties of hardmetal feedstocks and process conditions were discussed and examples of IM parts were presented. NUMERICAL SIMULATION OF COMPACTION AND SINTERING OF CEMENTED CARBIDE D. Bouvardet et al. (Inst. National Polytechnique, Grenoble, France.) Shape changes during sintering were discussed with regard to green density gradients and consequent heterogeneous streses. Simulation of pressing and sintering was shown to allow prediction of final shape. Simulation of processing a WCCo part was discussed. Compaction was described by equations, parameters being estimated by experiment. A linear viscous model was used for sintering. Predictions were compared with experiment. MICROWAVE SINTERING OF IL4RDMETALS AND CERAMICS M. WillertPorada et al. (University of Dortmund, Dortmund, Germany.) Application of microwaves to sintering was discussed with reference to properties of hardmetals, new materials and researches on ceramics. Principles of interactions between microwaves and hardmetals and ceramics were outlined. Results on AlzOa, Al,Oa-TX and WC-Co were presented. Mechanical properties of WC-Co were given. The potential of microwave heating, for sintering, was reviewed. 38
MPR February
1997
MACROSCOPIC AND MICROSTRUCTURAL EVOLUTION IN TUNGSTEN CARBIDE IN SOLID STATE SINTERING J.M. Missiaen. (Laboratoire de Thermodynique et Physico-Chimie Metalluriques, France.) An investigation of structural evolution during solid state sintering of WC-Co, using various techniques, was described. Measurements of phases were made. Features of the sintering were characterized. The objective was to relate structure and shrinkage. DENSIFICATION DURING SINTERING OF TUNGSTEN CARBIDE-COBALT S. Haglund et al. (Royal Inst. of Technology, Stockholm, Sweden.) Densification of WC-Co in the solid state was discussed and it was noted that this can account for up to 75% of the total sintering densiEcation. Dilatometry, with and without a small, 1 MPa, load, was used to study solid state sintering. The results were discussed, mechanisms identified and a model was proposed. Use of the model in other systems was considered. INJECTION MOULDING OF TUNGSTEN CARBIDE-COBALT USING TWO BINDER SYSTEMS M. Youseffi, I.A. Menzies. (University of Loughborough, Loughborough, UK) A study of injection moulding of WCGwt%Co was described. Two binder systems were used. One was based on waxes. The other was water soluble polyvinyl alcohol based. Optimum feedstock compositions were formulated and rheological properties investigated. A high solids loading of 65% was reported with high densities attained.
Properties
and testing
SINTERING AND PROPERTIES OF TUNGSTEN CARBIDE-COBALT RELATED TO POWDER PROPERTIES B. Roebuck et al. (National Physical La boratory, Teddington, Middlesex, UK) A study of sintering of WC-Co, with a wide range of grain sizes, was described. Sintering, structure and properties were correlated with powder characteristics. HARDMETALS AND THERMODYNAMIC MODELLING B. Uhrenius. (Sandvik Hardmetals, Sweden.) Computer programs and databases were discussed with regard to calculation of alloy thermodynamics, phase equilibria and development of new alloy grades. In respect of cemented carbides these tools are used to describe relationships between process conditions and structure. Processing can be described mathematically
by use of computer programs. Applications to WC-Co and multi-component systems were outlined. FINE GRAINED TUNGSTEN CARBIDEVANADIUM CARBIDE-COBALT HARDMETAL D. Whitefield et al. (University of the Witwatersrand, South Africa.) Preparation of WC-12wt”%VC-lO%Cowas described. The mean particle sizes were, WC, less than 1 urn and VC, about 2 pm. Properties of the material were presented. Vicker’s hardness at 1700 is higher than WC-6%Co and the toughness is also higher. INFLUENCE OF GRAIN SIZE ON HARDNESS AND TOUGHNESS OF TUNGSTEN CARBIDE-COBALT Y. Milman et al. (Academy of Sciences of the Ukraine, Kiev, Ukraine.) Hardness and fracture toughness of WCCo were investigated in the range -196 to 900°C as a function of WC grain size. A HallPetch type of relationship was found. Thermal softening was reported to decrease with decrease in WC grain size. EFFECT OF POROSITY ON TRANSVERSE RUPTURE AND FRACTURE TOUGHNESS OF A TWO PHASE ALLOY A. Laptev. (Academy of Sciences of the Ukraine, Kiev, Ukraine.) It was reported that at some value of relative porosity fracture toughness and yield strength of plastic materials are increased. Effect of porosity of brittle materials was discussed with regard to pore size. A study of the effects of porosity on transverse rupture strength and fracture toughness of a hard metal with 24% of a plastic phase was described. Variation in porosity was attained by variation of hot pressing conditions. TESTING AND GRAIN SIZE OF TUNGSTEN CARBIDE POWDERS - POST SINTERING CHARACTERIZATION P. Klapetek, J. Spacil. (Pramet as., Czech Republic.) An investigation of WC-lO%Co hardmetals, made from differing grades of WC, was described. A milling test was proposed and parameters requiring control were identified.
Coatings and ultrahard materials CHEMICALLY VAPOUR DEPOSITED DIAMOND CUTTING TOOL APPLICATIONS IN COMPOSITE MATERIALS R. Hay. (Norton Diamond Film Co., USA) CVD diamond cutting tools were reviewed. It was reported that thick and