Carbide and binder phases in cemented carbides

Carbide and binder phases in cemented carbides

Re, in the range 0 to 2% was a d d e d to WC-10%Co alloys, s i m i l a r s i n t e r i n g behaviour to non-Re alloys was found. There was an increase...

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Re, in the range 0 to 2% was a d d e d to WC-10%Co alloys, s i m i l a r s i n t e r i n g behaviour to non-Re alloys was found. There was an increase in h a r d n e s s for the Re alloys which were rich in WC but the transverse rupture strength was unchanged.

HIGH P R E S S U R E S I N T E R I N G OF DIAMOND BY A GLASSY CARBON A D D I T I O N M.Miyamoto et al, (Kobe Steel Ltd. Akashi, J a p a n ) . Int, J. Refractory Metals and Hard Materials, No 1 10, No 1, 1991, 27-31. High p r e s s u r e sintering, by a solvent metal infiltration technique, of d i a m o n d particles in an a m o r p h o u s carbon m a t r i x has been investigated. Transformation of a m o r p h o u s carbon to d i a m o n d was found to p r o m o t e infiltration of the metal. A well s i n t e r e d d i a m o n d material, with a fine h o m o g e n e o u s m i c r o s t r u c t u r e a n d high hardness, was obtained with material c o n t a i n i n g 70 to 80% d i a m o n d in t h e starting material. Wear resistance of t h e material was assessed.

STRUCTURE OF THE BINDING PHASE IN RHENIUM ALLOYED COBALT C E M E N T E D T U N G S T E N CARBIDES A.F.Lisovsky et al, (Ukraine Academy of Sciences, Kiev, USSR). Int, J, Refractory Metals and Hard Materials No 1 10, No 1, 1991, 33-36. Electron microscopy was used to study the structure of the m a t r i x in WC-Co alloys to which Re had been added. Re was found to dissolve in t h e Co matrix. Re reduces the stacking fault energy and p r o m o t e s the m a r t e n s i t i c t r a n s f o r m a t i o n CoB to Coe, Control of the Co m a t r i x structure and p r o p e r t i e s w e r e d e m o n s t r a t e d t o be possible.

FORMATION OF IMPURITY CONTAINING P H A S E S IN C E M E N T E D CARBIDES B.Uhrenius et al, (Swedish Inst for Metals Research, Stockholm, S w e d e n ) . Int, J.

Refractory Metals and Hard Materials, No 1 10, No 1, 1991, 45-55. Cemented carbides containing oxide and sulphide inclusions were investigated, Al, Si, Ca and P were a d d e d to the raw materials and S and O were i n t r o d u c e d by increasing the O or S potentials in the sintering atmospheres causing precipitation of the inclusions. The result were compared with calculated phase equilibria. The inclusions formed u n d e r various conditions of alloy and a t m o s p h e r e compositions were described. It was found t h a t CaS was always formed in presence of Ca and S.

APPLICATION OF TITANIUM COATINGS TO BORON NITRIDE V.G.Aleshin et al, Poroshkovaya Metallurgiya, No 4, 1991, 40-44, (In Russian). Ti coatings were applied to cubic BN and subjected to heat treatment. The interactions between the coating and the s u b s t r a t e were examined. BN, TiN and oxides were detected after t r e a t m e n t at 955°C. This is a t t r i b u t e d to diffusion of N and B into the Ti coating. D E N S I F I C T I O N OF SILICON NITRIDE BY HIGH G A S E O U S P R E S S U R E P.S.Kisly et al, Poroshkovaya Metallurgiya, No 4, 1991, 44-48, (In Russian). Densification of SiN by hot isostatic pressing (HIP) was studied. An inverse t e m p e r a t u r e relationship for densification in Ar of powders with a high specific surface was found. A more c o m p l e x situation was noted in specimens t r e a t e d in N d e p e n d i n g on additives and p h a s e composition. Fe was found to cause increased shrinkage with p r e s s u r e and for 0 the inverse relationship is found. In the cases of powders with low specific surface the effects of p r e s s u r e on densification are less pronounced. OXIDATION OF COATINGS ON DIAMOND V.G. C h u p r i n a et al, Poroshkovaya Metallurgiya, No 4, 1991, 53-58, (In Russian). The oxidation of Mo and Mo-Ni coatings on d i a m o n d s u b s t r a t e on heating in air, at 750 a n d 850°C, w a s i n v e s t i g a t e d by t h e r m o g r a v i m e t r i c a n a l y s i s a n d X-ray diffraction. Accumulation of oxides in the scale a n d loss of volatile oxides were found, Carbides were formed. The scale was rich in NiO due to the loss of MoO 3 by sublimation. INTERPHASE REACTIONS IN CHROMIUM C E M E N T E D TITANIUM CARBIDE AND CARBONITRIDE F.F.Egorov et al. Poroshkovaya Metallurgiya, No 4, 1991, 69-74, (In Russian). Interactions between TiC and Ti(C,N) and liquid Cr during liquid p h a s e sintering were studied. In the case of the TiC a t h r e e p h a s e structure was d e t e c t e d due to t h e formation of Cr3C 2 in accordance with the thermal equilibrium diagram. In the case of the carbonitride t h e r e was denitriding of the solid p h a s e as CrN2 was formed. The findings are r e p o r t e d to limit the use of Cr for liquid p h a s e s i n t e r i n g of TiC a n d Ti(C,N) h a r d metals due to reduction in properties. STRUCTURE FORMATION IN T U N G S T E N / C H R O M I U M CARBIDENICKEL HARD METALS V.P.Bondarenko et al, Poroshkovaya Metallurgiya, No 4, 1991, 85-89, (In Russian). E f f e c t s o f Cr3C2, u s e d in p a r t i a l

r e p l a c e m e n t for WC, in Ni c e m e n t e d carbides was studied. A three phase structure was observed above 15wt% Cr carbide. The p r e s e n c e of Cr carbide is r e p o r t e d to r e d u c e t h e q u a l i t y of Ni c e m e n t e d WC materials. CARBIDE AND B I N D E R P H A S E S IN C E M E N T E D CARBIDES G.S.Upadhyaya, (Indian Inst of Technology, Kanpur, India). Rev, Powder Metallurgy

and Physical Ceramics, Vol 4, No 1, 1990, 59-78. The c a r b i d e a n d b i n d e r p h a s e s in c e m e n t e d c a r b i d e s are d i s c u s s e d w i t h r e s p e c t to t h e o r d e r in w h i c h e a c h composition was developed. The scientific b a s e s underlying t h e selection of each combination of binder (Fe, Co, Ni, Mo, Cr and steel) and carbide (carbides of W, Ti, Ta, Hf, and Hb) are considered. An a t t e m p t is m a d e to rationalize the classification of c e m e n t e d carbide materials in order to ensure efficient application. TECHNOLOGICAL D E F E C T S IN COATINGS ON C E M E N T E D CARBIDES P . P e l t a n , Pokroky Praskove Metallurgie, No 4, 1990, 5-19, ( I n C z e c h ) . The application of chemical a n d physical vapour d e p o s i t e d coatings on cutting tool materials is reviewed with consideration given to composition, thickness, a d h e s i o n of t h e coating, structure and defects. Coating tools of differing appearance were e x a m i n e d and service lives investigated. APPLICATION OF POLYCRYSTALLINE DIAMOND FOR D R E S S I N G OF GRINDING WHEELS J . D o u b r a v s k y a n d J. Havlcek. Pokroky Praskove MetaUurgie, No 4, 1990, 20-27, (In Czech). A description is given of polycrystalline d i a m o n d b o n d e d with a ceramic p h a s e for use as grinding material. Laboratory and service t e s t s are outlined.

Intermetallic materials MICROSTRUCTURE OF NICKELTITANIUM SME ALLOYS M.Zhu et al. (Dalian Univ of Technology, Dalian, China). Acta Metall, Materia, Vol 39, No 7, 1991, 1481-1487. The m i c r o s t r u c t u r e of Ni-To, s h a p e memory effect (SME) alloys, which had been p r o d u c e d by explosive compaction followed by h e a t t r e a t m e n t h a s b e e n investigated. The extensive formation of TiNi intermetallic is d e m o n s t r a t e d and a g o o d SME w a s o b t a i n e d . D i f f e r e n c e s between PM and c a s t / w r o u g h t SME alloys were reported. Other Ti-Ni intermetallic were detected.

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