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Effect of boron source on structure and properties of molybdenum-nickel-boride hard alloys
particular requirement, ductility at low temperature, was considered. Strengthening methods, solid solution hardening and particle reinforcement were outlined. It is concluded that vacuum melting methods yielded alloys with highest properties and PM methods the lowest COSTS,
Bubble deformation durln8 drawlnl of tunpten wire L.Bartha etal. (Hungarian Academmy of Sciences, Budapest, Hungary.) Int. J. Refract. Metals/Hard Mater., Vol 20, No /4, 2002, 295-299.
Rods and wires of K-Si-AI doped W, containing residual porosity and K filled bubbles, were drawn from 6ram to 0.2ram. Deformation of K filled bubbles were studied with regard to changes in size and shape and density of populations of bubbles. It was found that the changes in bubble shape was less than predicted, about 1/d instead of l/d3 where d is the wire diameter. A 'constant volume' assumption seemed to be more reliable than 'constant length'. Spherical bubbles were detected after some wire drawing.
temperature coefficient. Further reduction was attained by addition of MgA1204. The decrease is attributed to reaction between titanate and spinel species.
Chemical pretrsstment of hardmetai substrates for diamond deposition
Cermets Effect of boron source on structure end properties of molybdenum-nlckel-borlde hard alloys Y.Yamasaki et al. (Toyo Kohan Co. Ltd., Kudamatsu, Japan.) J.Japan Soc Powder/Powder Metall., Vol 48, No 7, 2ool, 643-647. In Japanese. It is reported that Ni-46.gwt%Mo12.5%V-4.5%B alloys had been prepared using MoB, Mo2B, NiB or Ni2B as sources of B to study the effects of boride type on structure and properties. Samples made from Ni2B showed a fine two-phase microstructure with homogeneous distribution of borides and had transverse rupture strength above 3GPa. Alloys made from other source borides only reached 2.2 to 2.6GPa. Carbon, as impurity in raw materials resulted in reduction in mechanical properties due to formation of carbides and changed composition of the borides.
Coatings
Ceramics
Overlay of borlde cermet by welding
Hot pressln$ In alumina-chromium oxide system
K.Hamashima, K.Sato. (Asahi Glass Co. Ltd., Yokohama, Japan.) Acta Mater., Vol 51, No i, 2o03,665-669. In Japanese. It is reported that a horide cermet coating had been deposited by plasma transfer arc welding on carbon steel subsrrates. Composite, semi-sintered powders, based on MoB and Ni were used. The coating microstucture consisted on Mo2NiB 2 in a Ni matrix but this was difficult to control. Better results were obtained with additions of CrB and Fe, which gave M%(Fe,Cr)B 2.
M.T.Hernandez et al. (CIEMAT, Madrid, Spain.) Acta Mater., Vo151, No i, 2003, 217-228.
Properties of Also 3 are discussed with regard to effects of additions such as Cr and problems in densification of binary mixtures. Hot pressing , at 1300°C, as a means of attaining high density of A120~-(0 to 6)wt%Cr203 powder made by the Pechini method, was evaluated experimentally. C-diffusion and microstructures of densified materials were studied to assess hot pressing as a feasible technique.
Forsterlte ceramics for microwave appUcstlons N.Shibata et al (Japan Fine ceramics Centre, Nagoya, Japan.) JJapan Soc Powder/Powder Metali.,Vol 48, No 9, 2ooi, 784-789 .In English.. It is reported that forsterite ceramics, doped with CaTiO 3 and MgAI204 had been prepared in an effort to decrease the effect of temperature on dielectric permittivity. Doping with CaTiO~ reduced the
34
M~ March 2003
deposits with graphite inclusions. Addition of fullerenes to the deposition gases is noted. Some microstructures are described.
Deposition of 'baUss' diamond and nano.crystsUlne diamond R.Haubner, B.Lux. (University of Technology, Vienna, Austria.) Int. J. Refract. Metals/Hard Mater., Vo120, No 1, 2002, 93-1oo Nano-crystalline diamond is discussed with regard to properties and types. 'Belles' diamond is nano-crystalline, also known as ball shaped and cauliflower-like, and can be made by chemical vapour deposition. Differences in morphology, due to variations in deposition conditions, are noted including flat types, faceted types and •
V.Buck et al. (University GH Essen, Essen, Germany.) Int. J. Refract. Metals/Hard Mater., Vo[ 20, No 1, 2002,101-105. It is noted that there may be poor adhesion between coating and hardmetal substrata in cutting tools. This is attributed to the graphitising effect of the Co or Ni binder on diamond coatings. The problem may be overcome by use of intermediate layers or chemical pretreatment of the substrata. Chemical treatment may be used to reduce the binder content in the surface layer. It is noted that while Murakami's reagent improves adhesion it enhances the binder content. This is attributed to formation of an oxide/hydroxide intermediate layer.
Multllayer costlnp containing diamond and other hard materials on hardmetal substrates R.Haubner et al. (University of Technology, Vienna, Austria.) Int. J. Refract. Metals/Hard Mater., Vol 2o, No 1, 2002, 107-113. Use of hard material coating to improve wear properties of cutting tools is discussed, in particular multilayer coatings. The possibility of combining diamond with other chemically vapour deposited hard materials, TiC, TiN, Ti(C,N) and AI203 was investigated. All these options could be realised, some showing good adhesion under strain. Technical possibilities are noted.
Diamond films for wear protection of hsrdmetal tools F.Deuerler etal. (University Gesamthochschule W~ppertal, WiJppertal, Germany.) int. J. Refract. Metals/Hard Mater., Vol 20, No 1, 20o2, 115-120. It is reported that polycrystalline high quality diamond coatings had been applied to hardmetal tools by a novel 'uniform space exitation' ~iprocess. Strong adhesion of the coating is ensured by pretreatment of the WC-6wt%Co substrata. Wear resistance was assessed by cavitation tests. Effects of coating structure, thickness and adhesion on wear were evaluated. The coated material was shown to have industrial potential.
metal-powder.net
Bubble deformation durln8 drawlnl of tunpten wire L.Bartha etal. (Hungarian Academmy of Sciences, Budapest, Hungary.) Int. J. Refract. Metals/Hard Mater., Vol 20, No /4, 2002, 295-299.
Rods and wires of K-Si-AI doped W, containing residual porosity and K filled bubbles, were drawn from 6ram to 0.2ram. Deformation of K filled bubbles were studied with regard to changes in size and shape and density of populations of bubbles. It was found that the changes in bubble shape was less than predicted, about 1/d instead of l/d3 where d is the wire diameter. A 'constant volume' assumption seemed to be more reliable than 'constant length'. Spherical bubbles were detected after some wire drawing.
temperature coefficient. Further reduction was attained by addition of MgA1204. The decrease is attributed to reaction between titanate and spinel species.
Chemical pretrsstment of hardmetai substrates for diamond deposition
Cermets Effect of boron source on structure end properties of molybdenum-nlckel-borlde hard alloys Y.Yamasaki et al. (Toyo Kohan Co. Ltd., Kudamatsu, Japan.) J.Japan Soc Powder/Powder Metall., Vol 48, No 7, 2ool, 643-647. In Japanese. It is reported that Ni-46.gwt%Mo12.5%V-4.5%B alloys had been prepared using MoB, Mo2B, NiB or Ni2B as sources of B to study the effects of boride type on structure and properties. Samples made from Ni2B showed a fine two-phase microstructure with homogeneous distribution of borides and had transverse rupture strength above 3GPa. Alloys made from other source borides only reached 2.2 to 2.6GPa. Carbon, as impurity in raw materials resulted in reduction in mechanical properties due to formation of carbides and changed composition of the borides.
Coatings
Ceramics
Overlay of borlde cermet by welding
Hot pressln$ In alumina-chromium oxide system
K.Hamashima, K.Sato. (Asahi Glass Co. Ltd., Yokohama, Japan.) Acta Mater., Vol 51, No i, 2o03,665-669. In Japanese. It is reported that a horide cermet coating had been deposited by plasma transfer arc welding on carbon steel subsrrates. Composite, semi-sintered powders, based on MoB and Ni were used. The coating microstucture consisted on Mo2NiB 2 in a Ni matrix but this was difficult to control. Better results were obtained with additions of CrB and Fe, which gave M%(Fe,Cr)B 2.
M.T.Hernandez et al. (CIEMAT, Madrid, Spain.) Acta Mater., Vo151, No i, 2003, 217-228.
Properties of Also 3 are discussed with regard to effects of additions such as Cr and problems in densification of binary mixtures. Hot pressing , at 1300°C, as a means of attaining high density of A120~-(0 to 6)wt%Cr203 powder made by the Pechini method, was evaluated experimentally. C-diffusion and microstructures of densified materials were studied to assess hot pressing as a feasible technique.
Forsterlte ceramics for microwave appUcstlons N.Shibata et al (Japan Fine ceramics Centre, Nagoya, Japan.) JJapan Soc Powder/Powder Metali.,Vol 48, No 9, 2ooi, 784-789 .In English.. It is reported that forsterite ceramics, doped with CaTiO 3 and MgAI204 had been prepared in an effort to decrease the effect of temperature on dielectric permittivity. Doping with CaTiO~ reduced the
34
M~ March 2003
deposits with graphite inclusions. Addition of fullerenes to the deposition gases is noted. Some microstructures are described.
Deposition of 'baUss' diamond and nano.crystsUlne diamond R.Haubner, B.Lux. (University of Technology, Vienna, Austria.) Int. J. Refract. Metals/Hard Mater., Vo120, No 1, 2002, 93-1oo Nano-crystalline diamond is discussed with regard to properties and types. 'Belles' diamond is nano-crystalline, also known as ball shaped and cauliflower-like, and can be made by chemical vapour deposition. Differences in morphology, due to variations in deposition conditions, are noted including flat types, faceted types and •
V.Buck et al. (University GH Essen, Essen, Germany.) Int. J. Refract. Metals/Hard Mater., Vo[ 20, No 1, 2002,101-105. It is noted that there may be poor adhesion between coating and hardmetal substrata in cutting tools. This is attributed to the graphitising effect of the Co or Ni binder on diamond coatings. The problem may be overcome by use of intermediate layers or chemical pretreatment of the substrata. Chemical treatment may be used to reduce the binder content in the surface layer. It is noted that while Murakami's reagent improves adhesion it enhances the binder content. This is attributed to formation of an oxide/hydroxide intermediate layer.
Multllayer costlnp containing diamond and other hard materials on hardmetal substrates R.Haubner et al. (University of Technology, Vienna, Austria.) Int. J. Refract. Metals/Hard Mater., Vol 2o, No 1, 2002, 107-113. Use of hard material coating to improve wear properties of cutting tools is discussed, in particular multilayer coatings. The possibility of combining diamond with other chemically vapour deposited hard materials, TiC, TiN, Ti(C,N) and AI203 was investigated. All these options could be realised, some showing good adhesion under strain. Technical possibilities are noted.
Diamond films for wear protection of hsrdmetal tools F.Deuerler etal. (University Gesamthochschule W~ppertal, WiJppertal, Germany.) int. J. Refract. Metals/Hard Mater., Vol 20, No 1, 20o2, 115-120. It is reported that polycrystalline high quality diamond coatings had been applied to hardmetal tools by a novel 'uniform space exitation' ~iprocess. Strong adhesion of the coating is ensured by pretreatment of the WC-6wt%Co substrata. Wear resistance was assessed by cavitation tests. Effects of coating structure, thickness and adhesion on wear were evaluated. The coated material was shown to have industrial potential.
metal-powder.net