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Deformation and fracture of tungsten heavy alloy from −150 to 800 °C
INTERACTIONS OF HARDMETAL SUBSTRATES DURING DEPOSITION OF DIAMOND B.Lux et al. (Technical University of Vienna, Vienna, Austria.) It was noted that the adhesion of diamond coatings to hardmetals is sensitive to composition of the substrate, in particular pick-up of C by low C materials. This retards deposition of diamond and weakens the interface. The problem was investigated with regard to diffusion of C into the substrate, the nature of carbides present and the depth of penetration. CUTTING PERFORMANCE OF SUBMICRON GRAINED TITANIUM CARBONITRIDE CERMETS T.Tanase et al. (Mitsubishi Materials Corporation, Ibaraki-Ken, Japan.) Cutting tools made from Ti(C,N) based cermets were reviewed. Inferior toughness, compared with cemented carbides was noted. It was reported that a submicron grade of Ti(C,N), with improved toughness and wear properties, had been developed. The cutting performance was discussed in relationship with properties and microstructure. REFRACTORY METALS FOR GLASS INDUSTRY USE J.Disam et al. (Schott Glaswerke AG, Mainz, Germany.) High-temperature applications of refractory metals, notably MO, were reviewed with regard to chemical and physical properties. Low oxidation resistance was noted to be a problem. Work on oxidation resistant coatings for MO, based on Al-Si, Si-&-Fe and Si-B-C!, were described. Sprayed and annealed and pack cementation coatings provide protection. DEFORMATION AND FRACTURE OF TUNGSTEN HEAVY ALLOY FROM -150 TO 8OO’C E.Pink et al. (Austrian Academy of Sciences, Loeben, Austria.) Tensile mechanical properties of 92.5%W heavy alloys were investigated. Below 400°C alloys behaved like body centred cubic metals. From 450 to 650°C a Portevin-le Chatelier effect was found indicating dynamic strain aging. Above 650°C strength and ductility declined. Fracture appearances were correlated with mechanical test results. BRITTLENESS TOUGHNESS AND THERMAL SHOCK RESISTANCE OF TUNGSTEN-COPPER COMPOSITE K.Mu et al. (Central Iron and Steel Research Inst., Beijing, China.)
Cracking caused by thermal shock in W-Cu was noted. A study of micro-cleavage morphology and fracture of W and W-Cu was described with reference to composition, Cu permeability and structure. Mechanical properties were reported to increase with %Cu infiltrated and improved structural homogeneity. Crack propagation and thermal stress fracture were discussed. Fracture toughness, Kit, and thermal shock resistance were calculated. STRUCTURE AND PROPERTIES OF TUNGSTEN-SILVRR CONTACT ALLOYS WITH RARE EARTH OXIDE ADDED K.Wojtasik, SStolarz. (Inst. of NonFerrous Metals, Gliwice, Poland.) An investigation of the effects of 0.5 to 2% CeO,, LazO, or Y,O, on sintering, structure and properties of W-Ag contact alloys was described. It was reported that there were improvements in welding and erosion properties. Loss of material in service was two to three times smaller than for standard W-Ag alloys. OPTIMIZATION OF DESIGN OF FUNCTIONALLY GRADED MATERIALS I.Igarashi et al. (Tokyo Tungsten Co Ltd, Toyama, Japan.) Design of functionally graded materials was discussed with reference to processing, structure, properties, applications and design problems. A method for optimization was suggested. A finite element procedure was used for analysis and a generic algorithm for optimization. It was shown that an optimized graded material can be designed automatically. MICROSTRUCTURAL EVOLUTION DURING SINTERING OF NIOBIUMTITANIUM OXIDE ALLOYS H.R.Z.Sandim, A.F.Padilha. (University of Sao Paulo, Brazil.) The role of TiO, in structural evolution of Nb-TiO, oxide dispersion strengthened alloys during sintering was discussed. Activation energies for sintering were calculated for Nb, Nb-(0.5 or l.O)wt%TiO, at 430, 310 and 230 kJ.mol-’ suggesting that TiO, enhanced sintering. Results of high vacuum 0 degassing were presented. TECHNOLOGICAL POTENTIAL OF LASER-ASSISTED HOT MACHINING PROCESSES FKlocke, T.Bergs. (Fraunhofer Production Technology, Germany.)
Inst. for Aachen,
It was reported that laser techniques can be used to machine difficult-tomachine materials. Investigations of laser assisted machining of ceramics, high performance steel and Co based alloys were described. It was shown that lasers reduce cutting forces, reduce tool wear and increase material removal rates. STUDIES OF PLASMA ASSISTED CHEMICAL VAPOUR DEPOSITION OF TITANIUM CARBIDE AND NITRIDE F.Holler et al. (Montanuniversitii, Loeben, Austria.) A plasma activated CVD process was used to deposit TiN, TiC and Ti(C,N) coatings onto cemented carbide substrates. The glow-discharge was activated by a pulsed DC potential. Coatings were characterized with respect to morphology, structure and applicability to cutting of steel. The coatings were comparable with conventional CVD coatings. CUBIC BORON NITRIDE FOR CUTTING NICKEL BASE MATERIALS I.A.Petrusha et al. (National Academy of Sciences of Ukraine, Kiev, Ukraine.) The efficiency of cubic BN base cutting tools in turning hard high temperature alloys was studied. The high wear resistance of cubic BN was discussed in terms of structure, properties and effects of process conditions. It was reported that high dispersity and strength had been attained by the use of two types of cubic BN which had differing properties. The materials was suitable for turning Ni base alloys. EFFECT OF PRODUCTION CONDITIONS ON STRUCTURE AND PROPERTIES OF CUBIC BORON NITRIDE N.P.Bezhenar et al. (National Academy of Sciences of the Ukraine, Kiev, Ukraine.) It was reported that cubic BN-AlN composites had been made by reaction sintering cBN-Al or by solid phase sintering of cBN-AlN mixtures. In reaction sintering, AlN and a PAlrich solid solution were formed. The reaction sintered material had the higher stacking fault density. Tetragonal distortion of the BN was only detected in solid-phase sintered alloys. The reaction sintered alloy had the better cutting performance. PRODUCTION AND APPLICATION OF FUNCTIONALLY GRADED CEMENTED CARBIDE MATERIALS J.Spacil. (Pramet, Sumperk, Republic.) (In German.)
Czech
MPR February 1998 41
Cracking caused by thermal shock in W-Cu was noted. A study of micro-cleavage morphology and fracture of W and W-Cu was described with reference to composition, Cu permeability and structure. Mechanical properties were reported to increase with %Cu infiltrated and improved structural homogeneity. Crack propagation and thermal stress fracture were discussed. Fracture toughness, Kit, and thermal shock resistance were calculated. STRUCTURE AND PROPERTIES OF TUNGSTEN-SILVRR CONTACT ALLOYS WITH RARE EARTH OXIDE ADDED K.Wojtasik, SStolarz. (Inst. of NonFerrous Metals, Gliwice, Poland.) An investigation of the effects of 0.5 to 2% CeO,, LazO, or Y,O, on sintering, structure and properties of W-Ag contact alloys was described. It was reported that there were improvements in welding and erosion properties. Loss of material in service was two to three times smaller than for standard W-Ag alloys. OPTIMIZATION OF DESIGN OF FUNCTIONALLY GRADED MATERIALS I.Igarashi et al. (Tokyo Tungsten Co Ltd, Toyama, Japan.) Design of functionally graded materials was discussed with reference to processing, structure, properties, applications and design problems. A method for optimization was suggested. A finite element procedure was used for analysis and a generic algorithm for optimization. It was shown that an optimized graded material can be designed automatically. MICROSTRUCTURAL EVOLUTION DURING SINTERING OF NIOBIUMTITANIUM OXIDE ALLOYS H.R.Z.Sandim, A.F.Padilha. (University of Sao Paulo, Brazil.) The role of TiO, in structural evolution of Nb-TiO, oxide dispersion strengthened alloys during sintering was discussed. Activation energies for sintering were calculated for Nb, Nb-(0.5 or l.O)wt%TiO, at 430, 310 and 230 kJ.mol-’ suggesting that TiO, enhanced sintering. Results of high vacuum 0 degassing were presented. TECHNOLOGICAL POTENTIAL OF LASER-ASSISTED HOT MACHINING PROCESSES FKlocke, T.Bergs. (Fraunhofer Production Technology, Germany.)
Inst. for Aachen,
It was reported that laser techniques can be used to machine difficult-tomachine materials. Investigations of laser assisted machining of ceramics, high performance steel and Co based alloys were described. It was shown that lasers reduce cutting forces, reduce tool wear and increase material removal rates. STUDIES OF PLASMA ASSISTED CHEMICAL VAPOUR DEPOSITION OF TITANIUM CARBIDE AND NITRIDE F.Holler et al. (Montanuniversitii, Loeben, Austria.) A plasma activated CVD process was used to deposit TiN, TiC and Ti(C,N) coatings onto cemented carbide substrates. The glow-discharge was activated by a pulsed DC potential. Coatings were characterized with respect to morphology, structure and applicability to cutting of steel. The coatings were comparable with conventional CVD coatings. CUBIC BORON NITRIDE FOR CUTTING NICKEL BASE MATERIALS I.A.Petrusha et al. (National Academy of Sciences of Ukraine, Kiev, Ukraine.) The efficiency of cubic BN base cutting tools in turning hard high temperature alloys was studied. The high wear resistance of cubic BN was discussed in terms of structure, properties and effects of process conditions. It was reported that high dispersity and strength had been attained by the use of two types of cubic BN which had differing properties. The materials was suitable for turning Ni base alloys. EFFECT OF PRODUCTION CONDITIONS ON STRUCTURE AND PROPERTIES OF CUBIC BORON NITRIDE N.P.Bezhenar et al. (National Academy of Sciences of the Ukraine, Kiev, Ukraine.) It was reported that cubic BN-AlN composites had been made by reaction sintering cBN-Al or by solid phase sintering of cBN-AlN mixtures. In reaction sintering, AlN and a PAlrich solid solution were formed. The reaction sintered material had the higher stacking fault density. Tetragonal distortion of the BN was only detected in solid-phase sintered alloys. The reaction sintered alloy had the better cutting performance. PRODUCTION AND APPLICATION OF FUNCTIONALLY GRADED CEMENTED CARBIDE MATERIALS J.Spacil. (Pramet, Sumperk, Republic.) (In German.)
Czech
MPR February 1998 41