Development of ultrafine binderless cemented carbides

Development of ultrafine binderless cemented carbides

Rev/ew, Vol 24, 1991, 21-26. The use of atomic absorbtion spectroscopy for d e t e r m i n a t i o n of Ti a n d W base alloys is described. The inter...

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Rev/ew, Vol 24, 1991, 21-26. The use of atomic absorbtion spectroscopy for d e t e r m i n a t i o n of Ti a n d W base alloys is described. The interfering effects of W, Ni a n d B a n d t h e solvent acids used to dissolve the samples are considered, B a n d A1 a r e r e p o r t e d to inhibit t h e interference of W a n d Ni with the analytical procedures. E F F E C T S OF COBALT ON MECHANICAL P R O P E R T I E S OF S I N T E R E D T U N G S T E N HEAVY ALLOYS

T.Kaneko. ( J a p a n e s e Defence Agency, Tokyo, J a p a n . ) J.Japan Soc, Powder and Powder Metallurgy, Vol 38, No 7, 1991, 864-871. (In Japanese.) The effects of Co a d d i t i o n s on t h e m e c h a n i c a l p r o p e r t i e s of W-Ni-Fe have been investigated. For a W c o n t e n t of 95.4% t h e best i m p r o v e m e n t was found at 0.5%Co. A t lower W c o n t e n t s , 91.8 to 93.4%W t h e Co r e q u i r e m e n t for b e s t p r o p e r t i e s w a s 1.5%. The i n c r e a s e in properties is a t t r i b u t e d to better wettability of t h e W grains against t h e matrix. It is r e p o r t e d t h a t Co s t r e n g t h e n s t h e interfaces between m a t r i x a n d W grains a n d between W grains.

Zinc DENSIFICATION MECHANISM MAPS FOR HOT-PRESSED ZINC-ALUMINIUM ALLOYS

I~Isonishi et al. (Ritsumeikan University, J a p a n . ) J. Iron and Steel Inst. Japan, Vol 77, No 4, 1991, 536-543. (In Japanese.) The densification b e h a v i o u r of two Zn22at%A1 alloy powders is described. The two powders h a d different structures. One h a d a fine m i c r o d u p l e x (~ + ~,) s t r u c t u r e a n d t h e o t h e r was lamellar. The p o w d e r s were consolidated rates and hot-pressing parameter. The microduplex powder densified more rapidly to a higher density t h a n t h e lamellar. This is a t t r i b u t e d to superplasticity which was not found in t h e lamellar powder.

Electrical a n d M m a g n e t i c materials PRODUCTION OF SUPERCONDUCTING COPPER-NIOBIUM-TIN ALLOYS BY HOT EXTRUSION OF RAPIDLY SOLIDIFIED POWDER

A.Inoue et al. (Tohoku University, J a p a n . ) J. Materials Science, Vol 26, No 14, 1991, 3951-3954. The p r o d u c t i o n of s u p e r c o n d u c t i n g Cu5at%Nb-2.5%Sn alloys by h o t e x t r u s i o n of p o w d e r s is d e s c r i b e d . T h e p o w d e r is r e p o r t e d to c o n s i s t of finely d i v i d e d particles of Nb in a Cu-Sn m a t r i x a n d this

52 MPR June 1992

is r e t a i n e d d u r i n g consolidation. Nb3Sn is p r e c i p i t a t e d d u r i n g a n n e a l i n g at 650°C for 100 hours and this increases the superconducting transition temperature (Tc) from 8K to 15IL Values of m a g n e t i c p r o p e r t i e s , critical m a g n e t i c field a n d c u r r e n t density are given. The increase in Tc is a t t r i b u t e d to t h e presence of Nb3Sn.

H a r d m a t e r i a l s a n d tool steels DEVELOPMENT OF HIGH S T R E N G T H S I N T E R E D SILICON NITRIDE

T.Nishioka et ai. (Sumitomo Electric Hardm e t a l Ltd., Princes Risborough, Buckinghamshire, England.) Int. J. Refractory Metals & Hard Mate~als, Vol 10, No 3, 1991, 161-169. The use of sintered SiaN a in cutting tool a n d wear r e s i s t a n t applications is discussed w i t h r e g a r d to t h e p r o p e r t i e s of t h e m a t e r i a l s . The d e v e l o p m e n t of t h e s e materials in which grain size, s h a p e a n d aspect ratio are controlled is considered a n d t h e properties are r e p o r t e d to be high. Klc values of 5 to 7 M P a / m 1/2 t h e r m a l shock resistance of T=90OO°C, good acid resistance a n d Weibull m o d u l u s above 20 a r e r e p o r t e d . In p r o d u c t i o n of t h e s e materials a t t e n t i o n was paid to reduction of non-metallic inclusions. DEVELOPMENT OF ULTRAFINE B I N D E R L E S S C E M E N T E D CARBIDES

S.Imasato, ( N i p p o n T u n g s t e n Co. Ltd., Fukuoka, J a p a n . ) Nippon Tungsten Rev/ew, Vol 24, 1991, 5-12. The a d d i t i o n of h e x a g o n a l BN to WC6.5%Co powders, were t h e n consolidated by pressing a n d sintering is described. The BN a d d i t i o n s are r e p o r t e d to improve t h e sliding p e r f o r m a n c e u n d e r dry conditions in c o m p a r i s o n with conventional carbides. THERMODYNAMIC ANALYSIS OF SINTERING OF T U N G S T E N CARBIDECOBALT IN HYDROGEN

J.Leitner et ai. C ~ s o k a Skola ChemickoTechnolgicka, Praha, Czechoslovakia.) Pokroky Psaskove Metalurgie, No 1-2, 1991, 5.24. (In Czech.) The t h e r m o d y n a m i c s of sintering of Co c e m e n t e d WC h a s been studied in the range 725 ° to 1725°C as a function of H partial pressure a n d alloy composition. On the bases of t h e results t h e d i s t r i b u t i o n of C in carbide a n d m a t r i x was determined. LIQUID PHASE SINTERING OF TITANIUM NITRIDE ENRICHED HIGH S P E E D S T E E L S ( H S S ) AND MECHANICAL P R O P E R T I E S

P.g~Kar, G.S.Upadhyaya, ( I n d i a n I n s t i t u t e of technology, Kanpur, India). Steel Research, Vol 62, No 8, 1991, 352-357.

The p a p e r describes an investigation into the production, structures and properties of T15 HSS containing a d d i t i o n s of TiN. Cold c o m p a c t i o n a n d v a c u u m sintering to full density were used for consolidating of t h e w a t e r atomized powders. The r e s u l t s of s t r u c t u r e a n d p r o p e r t y tests are said to show t h a t t h e a l l o y s w i t h TiN e x h i b i t e q u i v a l e n t mechanical properties. S T U D I E S OF CERAMIC CUTTING TOOL MATERIALS A N D DEVELOPMENT OF MANUFACTURING TECHNOLOGY

M.Furukawa. (Nippon T u n g s t e n Co. Ltd., Fukuoka, J a p a n . ) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 62, 1991, 824-829. (In J a p a n e s e . ) The d e v e l o p m e n t of A1203 a n d SiaN4 cutting tools reinforced with TiC a n d SiC whiskers is described. Hot pressing a n d HIP have been used a n d are r e p o r t e d to result in e n h a n c e d strength and fracture toughness. E F F E C T OF FRACTURE T O U G H N E S S OF IMPACT PARTICLES ON EROSIVE WEAR O F C E R A M I C S

S.Wada. (Toyota Central Laboratories, Aichi, J a p a n . ) J.Japan Soc, Powder and Powder Metallurgy, Vol 38, No 7, 1991, 893-894. An investigation into t h e erosive wear of Si nitride a n d a l u m i n a by different types of a l u m i n a p a r t i c l e s is d e s c r i b e d . It is reported t h a t t h e e r o s i v e w e a r is p r o p o r t i o n a l to t h e fracture t o u g h n e s s of i m p a c t i n g particles.

IntermetaUic materials TITANIUM ALUMINIDE MADE BY SINTERING POWDER P R E P A R E D BY SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS ( S P H T S )

A.Mishima, S.Shite. (Nippon Tungsten co. Ltd., Fukouoka, J a p a n . ) Nippon Tungsten Review, Vol 21, 1991, 27-33. ~A1 powders were p r e p a r e d by SPHTS a n d consolidated by pressing a n d v a c u u m s i n t e r i n g , h o t p r e s s i n g o r HIP. T h e properties of t h e m a t e r i a l s are described as a f u n c t i o n of p r o c e s s c o n d i t i o n s . Significant differences are noted for t h e three process routes and properties increase in t h e order press a n d sinter, h o t press a n d HIP. P R O P E R T I E S OF AMORPHOUS MECHANICALLY ALLOYED ( M A ) TITANIUM-ALUMINIUM POWDERS

Y.H.Park et al. (Tohoku University, Sendai, J a p a n . ) - J . J a p a n Soc, Powder and PowderMetallurgy, Vol 38, No 7, 1991, 914-919. (In Japanese.) The p a p e r describes t h e effects of ball size on t h e a m o r p h i z a t i o n of Ti-50at%Al