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Structure and properties of hot-compacted silicon nitride-silicon carbide materials
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Ni and Mo in the zone between the carbide grains is described and a comparison is made between specimens which has been solid and liquid p h a s e sintered. E F F E C T OF ENVIRONMENT ON TEMPERATURE D E P E N D E N C E OF STRENGTH OF TITANIUM CARBIDE HARDMETALS O.V. Bakun et al, Poroshkovaya Metallurgiya, No 6, 1992, 80-83. (In Russian). Oxidation and mechanical properties of TiC with a Ni-Mo binder were investigated in the t e m p e r a t u r e range 20 to 1000°C. It is shown t h a t the strength of the alloy in air at 500 to 550°C is 30% lower t h a n in vacuum. This is attributed to the effects of oxidation and surface stresses. TWO STAGE GAS-STATIC COMPACTION OF SILICON NITRIDE P.S. Kisly et al, Poroshkovaya Metallurgiya, No 7, 1992, 18-23. (In Russian). The effects of pressure, t e m p e r a t u r e and time on the compaction and structural e v o l u t i o n o f Si:~Na-10% Y20:3 w e r e investigated for a two-stage gas thermal process. Shrinkage, weight loss, h a r d n e s s and fracture were analysed as functions of process conditions. It is shown t h a t to obtain high density the first stage must be at a low pressure. The growth of Si3N 4 crystals can be regulated by control of process conditions. STRUCTURE AND P R O P E R T I E S OF HOT-COMPACTED SILICON NITRIDESILICON CARBIDE MATERIALS A . A . . K a s i y a n e n k o et al, Poroshkovaya Metallurgiya, No 7, 1992, 52-57. (In Russian). An investigation of hot compaction of Si:3N4-SiC m a t e r i a l s , w i t h r e f e r e n c e to composition and particle size distribution, is described, MgO is shown to enhance hot compaction without affecting phase composition. The structure of the material is shown to be closely related to initial composition and particle size distribution. E F F E C T OF STRUCTURE ON ABRASIVE PROPERTIES OF TITANIUM CARBIDEIRON POWDERS E.G. Dyadko and M.D. Krymsky, Poroshkovaya MetaUurgiya, No 7, 1992, 67-71. (In Russian). The use of ferromagnetic abrasive TiC-Fe powders was investigated as functions of structure and the ability to cut and polish metal surfaces. Pores and, particularly, the edges of the TiC particles are shown to contribute to metal removal. USE OF D I S P E R S E D METALLIC B I N D E R FOR SINTERING OF TITANIUM-NIOBIUM CARBONITRIDE HARDALLOY I.V. Zalite et al, Poroshkovaya Metallurgiya,
LITERATURE
REVIEW
No 7, 1992, 79-83. (In Russian). It is reported t h a t high t e m p e r a t u r e evaporation had been used to p r o d u c e ultrafine Fe-Cr-Ni p o w d e r s w h i c h were used to sinter hard alloys based on (Ti, Nb) (C,N). The dispersion of the powders is shown to increase as the concentration of adsorbed gases, O and N, increase. The physico-mechanical properties of the h a r d alloy were investigated with respect to the concentration of binder, in the range 15 to 40 vol%. It is suggested t h a t alloys with 15 to 20% binder are suitable for use as cutting tools for intermediate and finish machining a n d 30 t o 40% b i n d e r a l l o y s a r e r e c o m m e n d e d for friction use. ELECTRON MICROSCOPIC STUDY OF FRACTURE CHARACTERISTICS OF TITANIUM BORIDE-IRON ALLOYS R.A. Andievsky et al, Poroshkovaya Metallurgiya, No 7, 1992, 83-86. (In Russian). An analysis of failure of TiB2-Fe alloys, over a w i d e r a n g e of t e m p e r a t u r e is presented. It is shown t h a t there is an increase in strength up to 600°C resulting from microplastic deformation. Above this there is a reduction in s t r e n g t h caused by general flow of the material. TiB2 grains b e c o m e i s o l a t e d n e a r to t h e e u t e c t i c temperatures, 1250 and 1350°C. Failure is attributed to quasi-brittle p h a s e separation and viscous flow of the binder. PRODUCTION AND PROPERTIES OF CORROSION RESISTANT TANTALUM CARBIDE BASED MATERIALS T.N. Shishkina et al, Poroshkovaya Metallurgiya, No 7, 1992, 101-106. (In Russian). The development of a corrosion resistant alloy based on Ta and Ti carbides in a steel m a t r i x is described. High t e m p e r a t u r e synthesis was used and bars of the alloy were produced. From the structure, p h a s e composition and mechanical properties it is deduced t h a t the material is suitable for use as electrodes in sulphate and nitrate electrolytes.
Injection moulding INTRODUCTION TO THE METAL INJECTION MOULDING PROCESS E.C. Lin, Metal Industries (China), Vol 25 No 2, 1991, 75-84. (In Chinese). MIM is described with reference to a flow chart of the process stages. Powder and b i n d e r r e q u i r e m e n t s are given. It is s u g g e s t e d t h a t t h e use o f MIM could e x p a n d at 40 and 50% per annum. D E B I N D I N G BEHAVIOUR OF INJECTION MOULDED ALUMINA COMPACTS T. Sasaki (Sumitomo Heavy Industries Ltd, Hiratsuka, J a p a n ) , J Japan Soc Powder
and Powder Metallurgy, Vol 40, No 2, 1993, 232-235. (In J a p a n e s e ) . The m e c h a n i s m s of debinding injection moulded alumina compacts were investigated with the object of minimizing t h e o c c u r r e n c e of defects. A wax/EVA b i n d e r w a s used. D e g r a d a t i o n of t h e binder resulted in a dark layer of material in t h e c o m p a c t on h e a t i n g , w i t h t h e unaffected material remaining white. It is p o s t u l a t e d t h a t t h e surface layer is a r e a c t a n t in t h e h e a t i n g process. From analysis of the kinetics of the reacting system it is suggested t h a t reactions at the interface between degraded and unchanged zones are rate determining.
Intermetallic materials DIFFUSION REACTION DURING MECHANICAL ALLOYING OF INTERMETALLIC MATERIALS A.K. Batacharya and E. Artz (Max Planck Inst Stuttgart, Germany), Scipta Metall Mater, Vol 27, No 5, 1992, 635-639. A model and analysis for diffusion and reaction occurring during MA o f i n t e r m e t a l l i c s with a high e n t h a l p y of mixing are presented. E m p h a s i s is placed on the role of diffusion in the evolution of m i c r o s t r u c t u r e . The e f f e c t o f p l a s t i c d e f o r m a t i o n in e n h a n c i n g diffusion is taken into account. It is shown t h a t the time required for MA can be predicted from a consideration of the elemental properties,
ARC SPRAY FORMING OF NICKEL ALUMINIDES A.P. Newbery and B. Cantor (University of Oxford, Oxford, UK), Seipta Metall Mater, Vol 27, No 7, 1992, 925-918. It is shown t h a t Ni aluminides, NiAl, Ni3Al and Ni2Al:3, can be formed by arc spray forming. Elemental wires were used as the starting material and problems of control of composition and porosity are noted. The use of cored wires resulted in production of low porosity materials with equiaxed structures.
FORMATION OF NANO-CRYSTALLINE BINARY INTERMETALLIC TITANIUM COMPOUNDS M. Qi et al, J Materials Science Letters, Vol l l , No 17, 1992, 1147-1150. It is shown t h a t a m o r p h o u s powders, p r e p a r e d by MA, can be converted into nano-crystalline intermetallic c o m p o u n d s by continued milling. In the e x p e r i m e n t s described fine Ti-Cu, Ti-Ni or Ti-Al powders w e r e p r o d u c e d . Ti-Cu p o w d e r s w e r e a m o r p h o u s after 40 hours and crystallized after 180 hours. In the case of Ti-Ni and TAl the c o m p a r a b l e t i m e s were 20 and 100 hours. The c ~ s t a l size is shown to be about 1 rim.
MPR September 1993 45
Ni and Mo in the zone between the carbide grains is described and a comparison is made between specimens which has been solid and liquid p h a s e sintered. E F F E C T OF ENVIRONMENT ON TEMPERATURE D E P E N D E N C E OF STRENGTH OF TITANIUM CARBIDE HARDMETALS O.V. Bakun et al, Poroshkovaya Metallurgiya, No 6, 1992, 80-83. (In Russian). Oxidation and mechanical properties of TiC with a Ni-Mo binder were investigated in the t e m p e r a t u r e range 20 to 1000°C. It is shown t h a t the strength of the alloy in air at 500 to 550°C is 30% lower t h a n in vacuum. This is attributed to the effects of oxidation and surface stresses. TWO STAGE GAS-STATIC COMPACTION OF SILICON NITRIDE P.S. Kisly et al, Poroshkovaya Metallurgiya, No 7, 1992, 18-23. (In Russian). The effects of pressure, t e m p e r a t u r e and time on the compaction and structural e v o l u t i o n o f Si:~Na-10% Y20:3 w e r e investigated for a two-stage gas thermal process. Shrinkage, weight loss, h a r d n e s s and fracture were analysed as functions of process conditions. It is shown t h a t to obtain high density the first stage must be at a low pressure. The growth of Si3N 4 crystals can be regulated by control of process conditions. STRUCTURE AND P R O P E R T I E S OF HOT-COMPACTED SILICON NITRIDESILICON CARBIDE MATERIALS A . A . . K a s i y a n e n k o et al, Poroshkovaya Metallurgiya, No 7, 1992, 52-57. (In Russian). An investigation of hot compaction of Si:3N4-SiC m a t e r i a l s , w i t h r e f e r e n c e to composition and particle size distribution, is described, MgO is shown to enhance hot compaction without affecting phase composition. The structure of the material is shown to be closely related to initial composition and particle size distribution. E F F E C T OF STRUCTURE ON ABRASIVE PROPERTIES OF TITANIUM CARBIDEIRON POWDERS E.G. Dyadko and M.D. Krymsky, Poroshkovaya MetaUurgiya, No 7, 1992, 67-71. (In Russian). The use of ferromagnetic abrasive TiC-Fe powders was investigated as functions of structure and the ability to cut and polish metal surfaces. Pores and, particularly, the edges of the TiC particles are shown to contribute to metal removal. USE OF D I S P E R S E D METALLIC B I N D E R FOR SINTERING OF TITANIUM-NIOBIUM CARBONITRIDE HARDALLOY I.V. Zalite et al, Poroshkovaya Metallurgiya,
LITERATURE
REVIEW
No 7, 1992, 79-83. (In Russian). It is reported t h a t high t e m p e r a t u r e evaporation had been used to p r o d u c e ultrafine Fe-Cr-Ni p o w d e r s w h i c h were used to sinter hard alloys based on (Ti, Nb) (C,N). The dispersion of the powders is shown to increase as the concentration of adsorbed gases, O and N, increase. The physico-mechanical properties of the h a r d alloy were investigated with respect to the concentration of binder, in the range 15 to 40 vol%. It is suggested t h a t alloys with 15 to 20% binder are suitable for use as cutting tools for intermediate and finish machining a n d 30 t o 40% b i n d e r a l l o y s a r e r e c o m m e n d e d for friction use. ELECTRON MICROSCOPIC STUDY OF FRACTURE CHARACTERISTICS OF TITANIUM BORIDE-IRON ALLOYS R.A. Andievsky et al, Poroshkovaya Metallurgiya, No 7, 1992, 83-86. (In Russian). An analysis of failure of TiB2-Fe alloys, over a w i d e r a n g e of t e m p e r a t u r e is presented. It is shown t h a t there is an increase in strength up to 600°C resulting from microplastic deformation. Above this there is a reduction in s t r e n g t h caused by general flow of the material. TiB2 grains b e c o m e i s o l a t e d n e a r to t h e e u t e c t i c temperatures, 1250 and 1350°C. Failure is attributed to quasi-brittle p h a s e separation and viscous flow of the binder. PRODUCTION AND PROPERTIES OF CORROSION RESISTANT TANTALUM CARBIDE BASED MATERIALS T.N. Shishkina et al, Poroshkovaya Metallurgiya, No 7, 1992, 101-106. (In Russian). The development of a corrosion resistant alloy based on Ta and Ti carbides in a steel m a t r i x is described. High t e m p e r a t u r e synthesis was used and bars of the alloy were produced. From the structure, p h a s e composition and mechanical properties it is deduced t h a t the material is suitable for use as electrodes in sulphate and nitrate electrolytes.
Injection moulding INTRODUCTION TO THE METAL INJECTION MOULDING PROCESS E.C. Lin, Metal Industries (China), Vol 25 No 2, 1991, 75-84. (In Chinese). MIM is described with reference to a flow chart of the process stages. Powder and b i n d e r r e q u i r e m e n t s are given. It is s u g g e s t e d t h a t t h e use o f MIM could e x p a n d at 40 and 50% per annum. D E B I N D I N G BEHAVIOUR OF INJECTION MOULDED ALUMINA COMPACTS T. Sasaki (Sumitomo Heavy Industries Ltd, Hiratsuka, J a p a n ) , J Japan Soc Powder
and Powder Metallurgy, Vol 40, No 2, 1993, 232-235. (In J a p a n e s e ) . The m e c h a n i s m s of debinding injection moulded alumina compacts were investigated with the object of minimizing t h e o c c u r r e n c e of defects. A wax/EVA b i n d e r w a s used. D e g r a d a t i o n of t h e binder resulted in a dark layer of material in t h e c o m p a c t on h e a t i n g , w i t h t h e unaffected material remaining white. It is p o s t u l a t e d t h a t t h e surface layer is a r e a c t a n t in t h e h e a t i n g process. From analysis of the kinetics of the reacting system it is suggested t h a t reactions at the interface between degraded and unchanged zones are rate determining.
Intermetallic materials DIFFUSION REACTION DURING MECHANICAL ALLOYING OF INTERMETALLIC MATERIALS A.K. Batacharya and E. Artz (Max Planck Inst Stuttgart, Germany), Scipta Metall Mater, Vol 27, No 5, 1992, 635-639. A model and analysis for diffusion and reaction occurring during MA o f i n t e r m e t a l l i c s with a high e n t h a l p y of mixing are presented. E m p h a s i s is placed on the role of diffusion in the evolution of m i c r o s t r u c t u r e . The e f f e c t o f p l a s t i c d e f o r m a t i o n in e n h a n c i n g diffusion is taken into account. It is shown t h a t the time required for MA can be predicted from a consideration of the elemental properties,
ARC SPRAY FORMING OF NICKEL ALUMINIDES A.P. Newbery and B. Cantor (University of Oxford, Oxford, UK), Seipta Metall Mater, Vol 27, No 7, 1992, 925-918. It is shown t h a t Ni aluminides, NiAl, Ni3Al and Ni2Al:3, can be formed by arc spray forming. Elemental wires were used as the starting material and problems of control of composition and porosity are noted. The use of cored wires resulted in production of low porosity materials with equiaxed structures.
FORMATION OF NANO-CRYSTALLINE BINARY INTERMETALLIC TITANIUM COMPOUNDS M. Qi et al, J Materials Science Letters, Vol l l , No 17, 1992, 1147-1150. It is shown t h a t a m o r p h o u s powders, p r e p a r e d by MA, can be converted into nano-crystalline intermetallic c o m p o u n d s by continued milling. In the e x p e r i m e n t s described fine Ti-Cu, Ti-Ni or Ti-Al powders w e r e p r o d u c e d . Ti-Cu p o w d e r s w e r e a m o r p h o u s after 40 hours and crystallized after 180 hours. In the case of Ti-Ni and TAl the c o m p a r a b l e t i m e s were 20 and 100 hours. The c ~ s t a l size is shown to be about 1 rim.
MPR September 1993 45