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Formation of titanium carbide during milling of elemental titanium and carbon powders
Ceramic materials SLIP CASTING OF MULLITE PARTS AND PROPERTIES OF SINTEBED MATERIALS
M.Maeda et al. (National Industrial Research Inst. of Nagoya, Nagoya, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 10451048. (In Japanese.) The use of slip casting to prepare sintered parts from mullite powder was studied with regard to the characteristics of the slurries used. The optimum amount of an organic polymer, added as a de-flocculant, was 0.2wt%. Green densities up to 60% were made by vacuum filtration and high sintered densities were attained by sintering at 1650°C in air for 3 hours. PHASE RELATIONSHIPS ALUMINA-ZIRCONIA
IN
S.N.Lakiza, L.M.Lopato. Poroshkovaya Metall., No 11/12, 1996, 51-58. (In Russian.) Phase relationships in metastable AlzOs-ZrO,-Y,O, were investigated. It is shown that a compound, Y,A150,, is synthesized during solidification of superheated melts.
Composite materials PRODUCTION AND SINTERING PROPERTIES OF MOLYBDENUMALUMINA COMPOSITES FROM COATED POWDERS
H.Kaga et al. (Hokkaido Industrial Technology Centre, Hakodate, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 1055-1060. (In Japanese.) It is reported that MO-A&O, composites had been prepared from MO-coated Also, powders with varying amounts of MO. Powders were coated by mechanofusion. The MO-Al,O, composite compacts were sintered by a plasma spark method. The composites made from the coated powders had higher densities than composites made from MO-Al,O, mixtures.
Electrical and magnetic materials HYDROGEN ABSORPTION NEODYMIUM-IRON-BORON MAGNETIC MATERIALS
IN
et al. (Sumitomo Metal Industries Ltd, Yamagasaki, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 978-983. (In Japanese.) Effect of milling methods on powder characteristics and hence on properties A.Saguchi
of sintered Nd-Fe-B magnets are discussed. A method of size reduction, H decrepitation, was investigated with reference to the effects of absorbed H on the magnetic materials. The mechanism of H absorption was elucidated. EFFECT OF ADDED IRON PHOSPHIDE POWDER ON MAGNETIC PROPERTIES OF SINTERED IRONCHROMIUM
TKato et al. (Daido Inst. of Technology, Nagoya, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 1013-1018. (In Japanese.) Effects of FeP, in PM Fe-12.5%Cr, on magnetic properties were investigated for AC and DC conditions. The highest magnetic properties were attained at 0.6% and 0.8% FeP for DC and AC conditions. Effects of density were determined. DC properties are increased with density. The effects are discussed with regard to formation of solid solutions.
Hard materials and tool steels REACTION OF TRANSITION METALS WITH CARBON AND IMPLICATIONS FOR SYNTHESIS OF DIAMOND
C.M.Sung, M.F.Tai. (National ChungCheng University, Chiayii, Taiwan.) ht. J. Refractory Metals Hard Mater., Vol 15, No 4, 1997,237-256. The carbide forming ability of metals is reviewed with respect to the number of vacancies in the d-orbitals in the electronic structure. Where this is zero, as in Cu and Zn, carbides are not formed. With a small number of vacancies, such as Fe, carbides are formed but Ti and V are strong carbide formers because of the numerous vacancies in the dorbitals. Metals of intermediate reactivity may catalyse transition of graphite to diamond. Formation of diamond from graphite at high pressure is discussed in terms of nucleation and growth. Catalysis by metals is modelled and it is predicted that Fe, Co, Ni, Mn and Cr are effective catalysts. These are used in commercial high pressure synthesis of diamond. NATURAL AND SYNTHETIC POLYCRYSTALLINE DIAMOND EMPHASIS ON BALLAS
WITH
B.Lux et al. (Technical University of Vienna, Vienna, Austria.) Znt. J. Refractory Metals Hard Mater., Vol 15, No 516, 1997, 263-288. Natural polycrystalline diamond exists in two forms, ballas and carbonado. Chemical vapour deposition of diamond at low pressure is discussed and the ability to deposit a polycrystalline
diamond ceramic is noted. Structures in synthetic diamond and ballas are compared. The possibility of making improvements in synthetic diamond are considered. FORMATION OF TITANIUM CARBIDE DUBING MILLING OF ELEMENTAL TITANIUM AND CARBON POWDERS
N.Q.Wu et al. (Zhejiang University, Hangzhou, China.) Int. J. Refractory Metals Hard Mater., Vol 15, No 515, 1997, 289-293. It is reported that elemental Ti and C powders had been ball milled and the synthesis of TiC monitored. It is concluded that mechanical alloying is a viable means of making Tic. NEW TYPES OF CEMENTED COATINGS ‘DIADUR’
CARBIDE
J.Subrt. (PRAMET a.s., Vyskumny Ustav Praskove Metal., Sumperk, Czech Republic.) Pokroky Praskove Metal., Vol 35, No 1, 1997, 14-23. (In Czech.) Wear resistant coatings on cemented carbide substrates are discussed. It is reported that new coatings, with graded structures, ‘Diadur’, have good adhesion. Results of cutting tests on steels, cast iron and stainless steels are presented. STABILITY OF NITROGEN IN TITANIUM CARBONITRIDE SOLID SOLUTIONS
S.Kang. (Seoul National University, Seoul, Korea.) Powder Metall., Vol 40, No 2, 1997, 139-142. Ti(C,N) is discussed. It is noted that N in solid solution in a TiC lattice improves cutting performance by refining structure. N in Ti(C,N) is considered to be unstable and this is explained by reference to the mixing behaviour of TiC and TIN. Loss of N from Ti(C,N) was investigated for different C:N ratios and little effect was found, indicating that the affinity of N for Ti, in Ti(C,N), is as strong as that of C. It is suggested that the system is fairly stable at high temperature. STRUCTURAL DEVELOPMENT AND SINTERING KINETICS OF CERAMIC REINFORCED HIGH SPEED STEEL
J.D.Bolton, A.J.Gant. (University of Bradford, Bradford, UK.) Powder Metall., Vol40, No 2, 1997, 143-151. Sintering and structural evolution in M2/3 HSS, with additions of NbC or Tic, were investigated. A supersolidus liquid phase sintering mechanism was found. NbC and TiC increased the minimum temperature required for sintering to full density but enlarged the sintering ‘window’ and restricted the formation of MPR May 1998 37
M.Maeda et al. (National Industrial Research Inst. of Nagoya, Nagoya, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 10451048. (In Japanese.) The use of slip casting to prepare sintered parts from mullite powder was studied with regard to the characteristics of the slurries used. The optimum amount of an organic polymer, added as a de-flocculant, was 0.2wt%. Green densities up to 60% were made by vacuum filtration and high sintered densities were attained by sintering at 1650°C in air for 3 hours. PHASE RELATIONSHIPS ALUMINA-ZIRCONIA
IN
S.N.Lakiza, L.M.Lopato. Poroshkovaya Metall., No 11/12, 1996, 51-58. (In Russian.) Phase relationships in metastable AlzOs-ZrO,-Y,O, were investigated. It is shown that a compound, Y,A150,, is synthesized during solidification of superheated melts.
Composite materials PRODUCTION AND SINTERING PROPERTIES OF MOLYBDENUMALUMINA COMPOSITES FROM COATED POWDERS
H.Kaga et al. (Hokkaido Industrial Technology Centre, Hakodate, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 1055-1060. (In Japanese.) It is reported that MO-A&O, composites had been prepared from MO-coated Also, powders with varying amounts of MO. Powders were coated by mechanofusion. The MO-Al,O, composite compacts were sintered by a plasma spark method. The composites made from the coated powders had higher densities than composites made from MO-Al,O, mixtures.
Electrical and magnetic materials HYDROGEN ABSORPTION NEODYMIUM-IRON-BORON MAGNETIC MATERIALS
IN
et al. (Sumitomo Metal Industries Ltd, Yamagasaki, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 978-983. (In Japanese.) Effect of milling methods on powder characteristics and hence on properties A.Saguchi
of sintered Nd-Fe-B magnets are discussed. A method of size reduction, H decrepitation, was investigated with reference to the effects of absorbed H on the magnetic materials. The mechanism of H absorption was elucidated. EFFECT OF ADDED IRON PHOSPHIDE POWDER ON MAGNETIC PROPERTIES OF SINTERED IRONCHROMIUM
TKato et al. (Daido Inst. of Technology, Nagoya, Japan.) J. Jpn. Sot. Powder Powder Metall., Vol 43, No 8, 1996, 1013-1018. (In Japanese.) Effects of FeP, in PM Fe-12.5%Cr, on magnetic properties were investigated for AC and DC conditions. The highest magnetic properties were attained at 0.6% and 0.8% FeP for DC and AC conditions. Effects of density were determined. DC properties are increased with density. The effects are discussed with regard to formation of solid solutions.
Hard materials and tool steels REACTION OF TRANSITION METALS WITH CARBON AND IMPLICATIONS FOR SYNTHESIS OF DIAMOND
C.M.Sung, M.F.Tai. (National ChungCheng University, Chiayii, Taiwan.) ht. J. Refractory Metals Hard Mater., Vol 15, No 4, 1997,237-256. The carbide forming ability of metals is reviewed with respect to the number of vacancies in the d-orbitals in the electronic structure. Where this is zero, as in Cu and Zn, carbides are not formed. With a small number of vacancies, such as Fe, carbides are formed but Ti and V are strong carbide formers because of the numerous vacancies in the dorbitals. Metals of intermediate reactivity may catalyse transition of graphite to diamond. Formation of diamond from graphite at high pressure is discussed in terms of nucleation and growth. Catalysis by metals is modelled and it is predicted that Fe, Co, Ni, Mn and Cr are effective catalysts. These are used in commercial high pressure synthesis of diamond. NATURAL AND SYNTHETIC POLYCRYSTALLINE DIAMOND EMPHASIS ON BALLAS
WITH
B.Lux et al. (Technical University of Vienna, Vienna, Austria.) Znt. J. Refractory Metals Hard Mater., Vol 15, No 516, 1997, 263-288. Natural polycrystalline diamond exists in two forms, ballas and carbonado. Chemical vapour deposition of diamond at low pressure is discussed and the ability to deposit a polycrystalline
diamond ceramic is noted. Structures in synthetic diamond and ballas are compared. The possibility of making improvements in synthetic diamond are considered. FORMATION OF TITANIUM CARBIDE DUBING MILLING OF ELEMENTAL TITANIUM AND CARBON POWDERS
N.Q.Wu et al. (Zhejiang University, Hangzhou, China.) Int. J. Refractory Metals Hard Mater., Vol 15, No 515, 1997, 289-293. It is reported that elemental Ti and C powders had been ball milled and the synthesis of TiC monitored. It is concluded that mechanical alloying is a viable means of making Tic. NEW TYPES OF CEMENTED COATINGS ‘DIADUR’
CARBIDE
J.Subrt. (PRAMET a.s., Vyskumny Ustav Praskove Metal., Sumperk, Czech Republic.) Pokroky Praskove Metal., Vol 35, No 1, 1997, 14-23. (In Czech.) Wear resistant coatings on cemented carbide substrates are discussed. It is reported that new coatings, with graded structures, ‘Diadur’, have good adhesion. Results of cutting tests on steels, cast iron and stainless steels are presented. STABILITY OF NITROGEN IN TITANIUM CARBONITRIDE SOLID SOLUTIONS
S.Kang. (Seoul National University, Seoul, Korea.) Powder Metall., Vol 40, No 2, 1997, 139-142. Ti(C,N) is discussed. It is noted that N in solid solution in a TiC lattice improves cutting performance by refining structure. N in Ti(C,N) is considered to be unstable and this is explained by reference to the mixing behaviour of TiC and TIN. Loss of N from Ti(C,N) was investigated for different C:N ratios and little effect was found, indicating that the affinity of N for Ti, in Ti(C,N), is as strong as that of C. It is suggested that the system is fairly stable at high temperature. STRUCTURAL DEVELOPMENT AND SINTERING KINETICS OF CERAMIC REINFORCED HIGH SPEED STEEL
J.D.Bolton, A.J.Gant. (University of Bradford, Bradford, UK.) Powder Metall., Vol40, No 2, 1997, 143-151. Sintering and structural evolution in M2/3 HSS, with additions of NbC or Tic, were investigated. A supersolidus liquid phase sintering mechanism was found. NbC and TiC increased the minimum temperature required for sintering to full density but enlarged the sintering ‘window’ and restricted the formation of MPR May 1998 37