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Thermodynamics in chemical vapour deposition of hard materials
Iron and steel Microstructural control for high-performance sintered low-alloy steels M.Matsuda, H.Miura. (Kumamoto University, Kumamoto, Japan.) J.Japan Soc Powder/Powder Metall., Vo[ 48, No 5, 2ooi,451-455. In Japanese. It is reported that addition of up to 8%Ni to 4600-0.4%C injection moulded steel increased mechanical properties, but only up to 6%Ni. This is attributed to solid solution hardening and to a microstructure consisting of a Ni-rich martensire in a network of tempered martensite. Effects of different types of Ni powder, spherical or acicular, on tensile and fatigue properties of Fe-6%Ni-0.5%Mo-0.2%Mn steel were investigated. Use of the acicular powder resulted in higher values of mechanical properties due to segregation of Ni when the spherical powder was used.
High-performance sintered low-alloy steels by high densification and microstructural control H.Miura et al, (Kumamoto University, Kumarnoto, Japan.) J.lapan Soc Powder/ Powder Metal/., Vol 48, No 5, 2ool,456460. In Japanese. Bi-modal Fe powders, 8 parts atomised angular 53 to 74ram and 2 parts carbonyl spherical 5ram, and acicular 4mm Ni powders were used to make steel samples. High density was attained by double press-double sinter means. This resulted in improved mechanical properties without loss of ductility due to solid solution hardenmg and a duplex microstructure. Use of nine parts coarse and one part fine powder lowered properties.
Magnesium Solid state reactions in Mg mechanically alloyed with addition of low melting point oxides A.Yamazaki et al. (Nihon University, Narashino, japan.) J.lapan Soc. Powder/Powder MetaH., Vol 48, No 5, 2ooi, 397-4o3 • In Japanese. Mg powder was mechanically alloyed, in At, with additions of SnO2, PbO or Sb203 and consolidated by vacuum hot pressing. Solid state reactions during pressing and subsequent heat treatment were investigated. Mg 2Sn, Mg2Pb, Mg2Sb3 and MgO wet formed. Microstructures and mechanical properties were studied.
metal-powder.net
Solid state reactions in Mg mechanically alloyed with metal silicides A.Yamazaki et al. (Nihon University, Narashino, Japan.) J.lapan Soc. Powder/Powder Metali., Vol 48, No 5, 2om,4o4-411. In Japanese. Mg powder was mechanically alloyed, in Ar, with additions of Ti, Cr and W silicides and consolidated by vacuum hot pressing. Precipitates of Mg silicides were formed by solid state reaction and Ti, Cr and W were dispersed in the Mg matrix.
Tungsten Nanometre high-density tungsten alloy EJingiian et al. (Central South University, Hunan, China.) PM Techno[ogy,Vol 19, No 4, 2001, 238-241. In Chinese. The current state of research into nanometre W alloys is reviewed with reference to production and processing of powder, sintering and applications of these materials.
Ceramic materials Graded mullite coatings S.N.Basu et al. (Boston University, Boston, USA.) Int. J. Refract. Metals/Hard Mater., Vo119, No 4-6, 2ool, 467-477. It is reported that compositionally graded, dense, uniform and crack free mullite, 3A1203.SiO2, coatings had been deposited on SiC by chemical vapour deposition. The AhSi ratio increased towards the outer surface. The structure was a mixture of yAl203 crystallites in a vitreous SiO 2 rich matrix. Phase changes in the coating during heat treatment at 1100°C to 1400°C were studied. Changes identified included a tetragonal to orthorhombic change, synthesis of mullite, devitrification of SiO 2, precipitation of At203 and twinning.
MuUite coatings on silicon based ceramics V.K.Sarin, M.L.Auger. (lonBond AG, Oiten, Switzerland.) Int. J. Refract. Metals/Hard Mater., Vo119, No 4-6, 2ooi, 479-494. Mullite coatings were deposited on SiC substrates by chemical vapour deposition from a mixture of A1CI3, SiC]4, CO 2 and H gases in a hot-wall vertical reactor. Intermediate reactions are shown to be significant to growth of mullite. Growth rate and structure of mullite depended on process conditions and gas mixture composition.
Coatings Coating properties optimised for tribological performance in cold forging and fine blanking applications F .Klocke, H.-W. Raedt. (RWl-H, Aachen, Germany.) int. ]. Refract. Metals/Hard Mater., Vol 19, No 4-6, 2ore, 495-5o5. Hard ceramic coatings on metal forming tools are reviewed. Results of characterisation of tribological conditions m cold forging and fine blanking are presented and models for friction and wear processes are developed. Coating properties are optimised and measured.
Microstructure and properties of chemical vapour deposited y alumina coatings A.Larsson, S.Ruppi. (Chalmers University of Technology, G6teborg, Sweden.) Int. J. Refract. Metals/Hard Mater., Vo119, No 4-6, 2ooi, 515-522. Microstructures and properties of CVD 7AIzO3 on TiN and Ti(C,N) precoated cemented carbides were investigated. The alumina was fine grained with {1,1,1} growth twins epitaxially grown on the substrates. Cutting performance is evaluated and compared with 1¢A12()3 coatings. The g coatings had slightly lower adhesion and a tendency for edge chipping but better crater wear reistance on the rake face.
Electrical and magnetic materials Effects of barium titanate on sintering and electrical properties of nickel electrode materials R.Ueyama et al. (Daiken Chemical Industry Corp., Osaka, Japan.) ].Japan Soc. Powder/Powder Metall., Vol 48, No 5, 2ool 392-396. In Japanese. Dispersability of BaTiO 3 ill Ni paste and the effects of the amount added oll sintering and electrical properties of Ni electrodes, for multi-layer capicitors, were investigated. BaTiO 3 reduced sintering shrinkage and increased the electrical resistivity. The amount of BaTiO 3 should not exceed 30%, above this the resistivity increased rapidly.
Hard materials and tool steels Thermodynamics in chemical vapour deposition of hard materials J.T.Wang et al. (Fudan University, Shanghai, China.) Int. J. Refract. Metals/Hard Mater., Vol 19, No 4-6, 2ool, 464-466 •
January 2003 ~
35
The 'thermodynamic paradox, connected with diamond growth and graphite etching, which violates the second law of thermodynamics, are discussed with reference to chemical vapour deposition. Calculation and experimental measurements were made of non-equilibrium phase diagrams, with good agreement. Non-equilibrium phase diagrams do not fit clasical thermodynamics and changes have bcen made. Partial non-equilibrium phase diagrams are presented for chemical vapour deposition of cubic BN.
Fabrication of titanium carbonitride based cermets with graded structure l.Konyashin. (Max-Planck Inst. for Metallforschung, Stattgart, Germany.) Int. J. Refract. Metals/Hard Mater., Vo[ 19, No 4-6, 2ooi, 523-526. It is reported that coated Ti(C,N)-Ni-Mo cermets, with composition and structure gradients, had been fabricated by a technique involving interaction between cermets and Cr vapour in vacuum. The coatings consisted of Cr carbide layer, 10mm thick on the outside and a l m m interlayer of Ni-Cr alloy between coating and substratc. Thered was a 100mm layer near the surface with graded structure and composition which is shown to have enhanced oxidation and corrosion resistance.
Effect of cubic phase composition on gradient zone formation in cemented carbides R.Frykholm et al. (Chalmers University of Technology, GOteborg, Sweden.) Int. J. Refract. Metals/Hard Mater., Vol 19, No 4-6, 2ooi, 527-538. Cemented carbide cutting tools with a surface zone depleted of carbide and enriched with binder were investigated. The results art" compared with simulations based on solution of multi-component diffusion equations and thermodynamic calculations. WC-Ti(C,N)-Co, WC-Ti(C,N)-NbC-Co and WC-Ti(C,N)-TaC-Co were studied. The surface zone is created by outward diffusion of N which leads to inward diffusion of Ti and a carbide depleted zone is created. The width of the the depleted zone is influenced by' the additions of TaC or NbC.
Tool wear in cutting sintered iron A.Ogura et al. (OSG Corp., Toyokawa, Japan.) ].Japan Soc. Powder/Powder Metall., Vol 48, No 5, 2ool, 386-391. In japanese.
3 6
January 2003
Tool life in cutting ferrous materials is discussed and an investigation of turning sintered Fe alloys is described. Cemented carbides, coated with (Ti,V)N, TiN or (Ti,A1)N, and ceramics, AI203-(0, 30 or 70)%TIC and Si3N4, were used at a cutting speed of 5m S~c-l. Lowest tool wear rates were found for (Ti,V)N and Si3N4. Abrasion was the main wear mechanism for ceramics.
Progress in titanium carbide composites H.¥.Chen et al. (Guilin Inst. of Technology. Guilin, China.) PM Industry, Vo111, No 3, 2ooi,38-44. In Chinese. It is noted that TiC composite materials are becoming more widely used. Research in progress is reported with reference to production technology, mechanical properties, rules for design and possible problems and their solutions.
Metal injection moulding Production of microporous metals R.Dwivedi, J.Fauerbach. (Southco Inc., Concrodville, USA.) PM Science/Technology Briefs, Vol 3, No 2, 2001, 22-25 . It is reported that a method for making microporous metals, with fine, closed pores and a fully dense surface skin, had been developed. This involves injection of gas, at high pressure, into the feedstock as it flows down the barrel of an injectionmoulding machine. Gas dissolves in the binder and is released as the feedstock passes the nozzle. Freezing of the feedstock arrests growth of gas bubbles. Pores are 5mm to 200mm in size. Pores are retained during debinding and sintering. Size and volume fraction of pores depends on process parameters. The process can also be used during extrusion.
Non-uniform shrinkage of injection moulded guide during sintering S.Takizawa et al. (Tohoku University, Sendal, Japan.) J.Japan Soc Powder/ Powder Metall., Vol 48, No 5, 2ooi,44545o • In Japanese In situ measurements of non-uniform shrinkage and distortion of a part during sintering were made by digital image correlation, to an accuracy of 3mm. Observed periodical shrinkage is attributed to non-uniform injection flow at opposite ends of the part and green density variations. Distortion due to gravity effects is estimated at 2 per cent.
SuperaUoys Structure and properties of udimet720 processed by hot isostatic pressing F.He, W.X.Wang. (Inst. of Aeronautical Materials, Beijing, China.) PM Industry, Vo111, NO 4, 2001,7"11. In Chinese. It is noted that Udimet720 is conventionally used in cast/wrought form. It is reported that PM materials processed by extrusion or forging have good mechanical properties. A study in which Udimet720 was processed by HIP and heat treatment is described. The properties are described and are shown to be comparable with extruded and forged alloys.
PM components Self lubricating bearing for mine cable S.H.Min et al. (Agricultural Machinery Research Inst., ChangSha, China.) PM Industry, Vo[ 11, No 3, 2ooi, 35-37. In Chinese. It is reported that PM had been used to produce self lubricating bearings for mining cable applications. The material was shown to perform better than alloy206 in terms of cost.
Development of aluminium PM composites for cylinder liners K.Azetsu, T.Hayashi. (Sumitomo Electric Industries Co. Ltd., Itami, Japan.) J.Japan Soc Powder/Powder Metall., Vol 48, No 5, 2ooi, 426-431. In Japanese. It is reported that cylinder liners for motorcycle engines had been made from rapidly solidified AI-17%Si-5%Fe3 . 5 % C u - 1 % M g - 0 . 5 % M n fine spherical alloy powder, with added graphite and A1203. The wear resistance is shown to be comparable with cast iron.
Miscellaneous Trends in rapid prototyping of parts from metal powders M.Imamura. (Sintokogio Ltd., Urawa, Japan.) J.]apan Soc Powder/Powder Metall., Vol 48, No 5, 2ooi, 415-421. In Japanese. Rapid prototyping of parts from metal powder is discussed in terms of its development from laser stereolithography. Initially a master model was copied. More recently layer lamination has been the basis of rapid prototyping. Recent developments are reviewed.
metal-powder.net
High-performance sintered low-alloy steels by high densification and microstructural control H.Miura et al, (Kumamoto University, Kumarnoto, Japan.) J.lapan Soc Powder/ Powder Metal/., Vol 48, No 5, 2ool,456460. In Japanese. Bi-modal Fe powders, 8 parts atomised angular 53 to 74ram and 2 parts carbonyl spherical 5ram, and acicular 4mm Ni powders were used to make steel samples. High density was attained by double press-double sinter means. This resulted in improved mechanical properties without loss of ductility due to solid solution hardenmg and a duplex microstructure. Use of nine parts coarse and one part fine powder lowered properties.
Magnesium Solid state reactions in Mg mechanically alloyed with addition of low melting point oxides A.Yamazaki et al. (Nihon University, Narashino, japan.) J.lapan Soc. Powder/Powder MetaH., Vol 48, No 5, 2ooi, 397-4o3 • In Japanese. Mg powder was mechanically alloyed, in At, with additions of SnO2, PbO or Sb203 and consolidated by vacuum hot pressing. Solid state reactions during pressing and subsequent heat treatment were investigated. Mg 2Sn, Mg2Pb, Mg2Sb3 and MgO wet formed. Microstructures and mechanical properties were studied.
metal-powder.net
Solid state reactions in Mg mechanically alloyed with metal silicides A.Yamazaki et al. (Nihon University, Narashino, Japan.) J.lapan Soc. Powder/Powder Metali., Vol 48, No 5, 2om,4o4-411. In Japanese. Mg powder was mechanically alloyed, in Ar, with additions of Ti, Cr and W silicides and consolidated by vacuum hot pressing. Precipitates of Mg silicides were formed by solid state reaction and Ti, Cr and W were dispersed in the Mg matrix.
Tungsten Nanometre high-density tungsten alloy EJingiian et al. (Central South University, Hunan, China.) PM Techno[ogy,Vol 19, No 4, 2001, 238-241. In Chinese. The current state of research into nanometre W alloys is reviewed with reference to production and processing of powder, sintering and applications of these materials.
Ceramic materials Graded mullite coatings S.N.Basu et al. (Boston University, Boston, USA.) Int. J. Refract. Metals/Hard Mater., Vo119, No 4-6, 2ool, 467-477. It is reported that compositionally graded, dense, uniform and crack free mullite, 3A1203.SiO2, coatings had been deposited on SiC by chemical vapour deposition. The AhSi ratio increased towards the outer surface. The structure was a mixture of yAl203 crystallites in a vitreous SiO 2 rich matrix. Phase changes in the coating during heat treatment at 1100°C to 1400°C were studied. Changes identified included a tetragonal to orthorhombic change, synthesis of mullite, devitrification of SiO 2, precipitation of At203 and twinning.
MuUite coatings on silicon based ceramics V.K.Sarin, M.L.Auger. (lonBond AG, Oiten, Switzerland.) Int. J. Refract. Metals/Hard Mater., Vo119, No 4-6, 2ooi, 479-494. Mullite coatings were deposited on SiC substrates by chemical vapour deposition from a mixture of A1CI3, SiC]4, CO 2 and H gases in a hot-wall vertical reactor. Intermediate reactions are shown to be significant to growth of mullite. Growth rate and structure of mullite depended on process conditions and gas mixture composition.
Coatings Coating properties optimised for tribological performance in cold forging and fine blanking applications F .Klocke, H.-W. Raedt. (RWl-H, Aachen, Germany.) int. ]. Refract. Metals/Hard Mater., Vol 19, No 4-6, 2ore, 495-5o5. Hard ceramic coatings on metal forming tools are reviewed. Results of characterisation of tribological conditions m cold forging and fine blanking are presented and models for friction and wear processes are developed. Coating properties are optimised and measured.
Microstructure and properties of chemical vapour deposited y alumina coatings A.Larsson, S.Ruppi. (Chalmers University of Technology, G6teborg, Sweden.) Int. J. Refract. Metals/Hard Mater., Vo119, No 4-6, 2ooi, 515-522. Microstructures and properties of CVD 7AIzO3 on TiN and Ti(C,N) precoated cemented carbides were investigated. The alumina was fine grained with {1,1,1} growth twins epitaxially grown on the substrates. Cutting performance is evaluated and compared with 1¢A12()3 coatings. The g coatings had slightly lower adhesion and a tendency for edge chipping but better crater wear reistance on the rake face.
Electrical and magnetic materials Effects of barium titanate on sintering and electrical properties of nickel electrode materials R.Ueyama et al. (Daiken Chemical Industry Corp., Osaka, Japan.) ].Japan Soc. Powder/Powder Metall., Vol 48, No 5, 2ool 392-396. In Japanese. Dispersability of BaTiO 3 ill Ni paste and the effects of the amount added oll sintering and electrical properties of Ni electrodes, for multi-layer capicitors, were investigated. BaTiO 3 reduced sintering shrinkage and increased the electrical resistivity. The amount of BaTiO 3 should not exceed 30%, above this the resistivity increased rapidly.
Hard materials and tool steels Thermodynamics in chemical vapour deposition of hard materials J.T.Wang et al. (Fudan University, Shanghai, China.) Int. J. Refract. Metals/Hard Mater., Vol 19, No 4-6, 2ool, 464-466 •
January 2003 ~
35
The 'thermodynamic paradox, connected with diamond growth and graphite etching, which violates the second law of thermodynamics, are discussed with reference to chemical vapour deposition. Calculation and experimental measurements were made of non-equilibrium phase diagrams, with good agreement. Non-equilibrium phase diagrams do not fit clasical thermodynamics and changes have bcen made. Partial non-equilibrium phase diagrams are presented for chemical vapour deposition of cubic BN.
Fabrication of titanium carbonitride based cermets with graded structure l.Konyashin. (Max-Planck Inst. for Metallforschung, Stattgart, Germany.) Int. J. Refract. Metals/Hard Mater., Vo[ 19, No 4-6, 2ooi, 523-526. It is reported that coated Ti(C,N)-Ni-Mo cermets, with composition and structure gradients, had been fabricated by a technique involving interaction between cermets and Cr vapour in vacuum. The coatings consisted of Cr carbide layer, 10mm thick on the outside and a l m m interlayer of Ni-Cr alloy between coating and substratc. Thered was a 100mm layer near the surface with graded structure and composition which is shown to have enhanced oxidation and corrosion resistance.
Effect of cubic phase composition on gradient zone formation in cemented carbides R.Frykholm et al. (Chalmers University of Technology, GOteborg, Sweden.) Int. J. Refract. Metals/Hard Mater., Vol 19, No 4-6, 2ooi, 527-538. Cemented carbide cutting tools with a surface zone depleted of carbide and enriched with binder were investigated. The results art" compared with simulations based on solution of multi-component diffusion equations and thermodynamic calculations. WC-Ti(C,N)-Co, WC-Ti(C,N)-NbC-Co and WC-Ti(C,N)-TaC-Co were studied. The surface zone is created by outward diffusion of N which leads to inward diffusion of Ti and a carbide depleted zone is created. The width of the the depleted zone is influenced by' the additions of TaC or NbC.
Tool wear in cutting sintered iron A.Ogura et al. (OSG Corp., Toyokawa, Japan.) ].Japan Soc. Powder/Powder Metall., Vol 48, No 5, 2ool, 386-391. In japanese.
3 6
January 2003
Tool life in cutting ferrous materials is discussed and an investigation of turning sintered Fe alloys is described. Cemented carbides, coated with (Ti,V)N, TiN or (Ti,A1)N, and ceramics, AI203-(0, 30 or 70)%TIC and Si3N4, were used at a cutting speed of 5m S~c-l. Lowest tool wear rates were found for (Ti,V)N and Si3N4. Abrasion was the main wear mechanism for ceramics.
Progress in titanium carbide composites H.¥.Chen et al. (Guilin Inst. of Technology. Guilin, China.) PM Industry, Vo111, No 3, 2ooi,38-44. In Chinese. It is noted that TiC composite materials are becoming more widely used. Research in progress is reported with reference to production technology, mechanical properties, rules for design and possible problems and their solutions.
Metal injection moulding Production of microporous metals R.Dwivedi, J.Fauerbach. (Southco Inc., Concrodville, USA.) PM Science/Technology Briefs, Vol 3, No 2, 2001, 22-25 . It is reported that a method for making microporous metals, with fine, closed pores and a fully dense surface skin, had been developed. This involves injection of gas, at high pressure, into the feedstock as it flows down the barrel of an injectionmoulding machine. Gas dissolves in the binder and is released as the feedstock passes the nozzle. Freezing of the feedstock arrests growth of gas bubbles. Pores are 5mm to 200mm in size. Pores are retained during debinding and sintering. Size and volume fraction of pores depends on process parameters. The process can also be used during extrusion.
Non-uniform shrinkage of injection moulded guide during sintering S.Takizawa et al. (Tohoku University, Sendal, Japan.) J.Japan Soc Powder/ Powder Metall., Vol 48, No 5, 2ooi,44545o • In Japanese In situ measurements of non-uniform shrinkage and distortion of a part during sintering were made by digital image correlation, to an accuracy of 3mm. Observed periodical shrinkage is attributed to non-uniform injection flow at opposite ends of the part and green density variations. Distortion due to gravity effects is estimated at 2 per cent.
SuperaUoys Structure and properties of udimet720 processed by hot isostatic pressing F.He, W.X.Wang. (Inst. of Aeronautical Materials, Beijing, China.) PM Industry, Vo111, NO 4, 2001,7"11. In Chinese. It is noted that Udimet720 is conventionally used in cast/wrought form. It is reported that PM materials processed by extrusion or forging have good mechanical properties. A study in which Udimet720 was processed by HIP and heat treatment is described. The properties are described and are shown to be comparable with extruded and forged alloys.
PM components Self lubricating bearing for mine cable S.H.Min et al. (Agricultural Machinery Research Inst., ChangSha, China.) PM Industry, Vo[ 11, No 3, 2ooi, 35-37. In Chinese. It is reported that PM had been used to produce self lubricating bearings for mining cable applications. The material was shown to perform better than alloy206 in terms of cost.
Development of aluminium PM composites for cylinder liners K.Azetsu, T.Hayashi. (Sumitomo Electric Industries Co. Ltd., Itami, Japan.) J.Japan Soc Powder/Powder Metall., Vol 48, No 5, 2ooi, 426-431. In Japanese. It is reported that cylinder liners for motorcycle engines had been made from rapidly solidified AI-17%Si-5%Fe3 . 5 % C u - 1 % M g - 0 . 5 % M n fine spherical alloy powder, with added graphite and A1203. The wear resistance is shown to be comparable with cast iron.
Miscellaneous Trends in rapid prototyping of parts from metal powders M.Imamura. (Sintokogio Ltd., Urawa, Japan.) J.]apan Soc Powder/Powder Metall., Vol 48, No 5, 2ooi, 415-421. In Japanese. Rapid prototyping of parts from metal powder is discussed in terms of its development from laser stereolithography. Initially a master model was copied. More recently layer lamination has been the basis of rapid prototyping. Recent developments are reviewed.
metal-powder.net