Influence of pressure sintering on properties of cemented carbides

Influence of pressure sintering on properties of cemented carbides

E F F E C T OF A D D I T I O N OF NICKEL BORIDE ON MECHANICAL P R O P E R T I E S AND WEAR RESISTANCE OF COPPER-TIN-LEAD ALLOYS T. Higuchi et al (Dai...

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E F F E C T OF A D D I T I O N OF NICKEL BORIDE ON MECHANICAL P R O P E R T I E S AND WEAR RESISTANCE OF COPPER-TIN-LEAD ALLOYS

T. Higuchi et al (Daido Metal Co, Inuyama, J a p a n ) , J. Japan Soc. Powder and Powder Metallurgy, Vol 40, No 8, 1993, 780-783. (In J a p a n e s e ) . It was r e p o r t e d t h a t t h e effects of t h e additions of Ni boride on t h e m e c h a n i c a l a n d wear p r o p e r t i e s of Cu-3.5wt%Sn-23%Pb b e a r i n g alloys h a d b e e n i n v e s t i g a t e d . Hardness and tensile strength were increased a n d t h e wear p r o p e r t i e s were improved by a factor of four for alloys w i t h 3 to 8wt% of t h e Ni boride.

Iron a n d s t e e l

Tantalum SINTERING OF D I S P E R S E D TANTALUM POWDERS

Y.V. Levinski et al (Moscow Inst. of Fine C h e m i c a l Technology, Moscow, Russia), Poroshkovaya Metallurgiya, No 12, 1992, 11-16. (In Russian). A study of t h e sintering of Ta powder, of different dispersions, at 1400 to 1800°C is d e s c r i b e d . T h e p h e n o m e n o n of z o n a l isolation is r e p o r t e d to be greater as t h e particle size is reduced. Pore sizes are r e p o r t e d to be d e p e n d e n t on particle size distribution. It is suggested t h a t surface diffusion a n d slip are t h e m e c h a n i s m s causing zonal isolation.

Tungsten R E C E N T DEVELOPMENTS IN FERROUS POWDER METALLURGY ALLOYS

W.B. J a m e s (Hoeganaes Corporation, Riverton, New Jersey, USA), Int. J. Powder Metallurgy, Vol 30, No 2, 1994, 157-162. A new a p p r o a c h to ferrous PM m a t e r i a l is described. This uses highly compressible high p e r f o r m a n c e powders m i x e d with a p a t e n t e d b i n d e r . To e n s u r e t h a t t h e properties and structures satisfy the r e q u i r e m e n t s of t h e applications t h e alloys are f o r m u l a t e d t a k i n g into a c c o u n t t h e process route. The powders are r e p o r t e d to have b e t t e r flow a n d die filling p r o p e r t i e s which leads to improved consistency in processing. The p r e s e n c e of t h e b i n d e r reduces alloy segregation. Alloy a n d p l a i n C steels can be made. It is r e p o r t e d t h a t f u r t h e r d e v e l o p m e n t s in alloy f o r m u l a t i o n a n d p r o c e s s t e c h n o l o g y will e n a b l e d e n s i t i e s of 7.3 t o 7.5 g m / c m 3 to be attained.

Titanium STRUCTURE A N D P R O P E R T I E S OF TITANIUM-CHROMIUM P R E P A R E D FROM ELEMENTAL POWDER MIXTURES

Y. Ikeda et al (Kyushi University, Fukuoka, J a p a n ) , J. Japan Soc. Powder and Powder Metallurgy, Vol 40, No 8, 1993, 774-779. (In J a p a n e s e ) . The sintering behaviour, s t r u c t u r e a n d p r o p e r t i e s of Ti-4wt%Cr, m a d e f r o m elemental powders mixtures were investigated. It is r e p o r t e d t h a t Cr does not affect t h e compatibility or sintering characteristics. Diffusion of Cr into t h e Ti is temperature dependent and 1 hour at 1100°C is required for homogenization. At 1200°© a density of 95% was attained. The alloy was ~ (body centred cubic) a t 1200°C ( w i t h p r e c i p i t a t e s of a (close p a c k e d h e x a g o n a l ) f o r m i n g d u r i n g cooling a t l°C/sec giving a fine ¢¢ + ~ s t r u c t u r e with good m e c h a n i c a l p r o p e r t i e s . F r a c t u r e characteristics are described a n d discussed.

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NOVEL T U N G S T E N ELECTRODE MATERIALS WITH RARE-EARTH ADDITIONS

Z. Wenlu et al (Tungsten a n d Molybdenum Plant, Beijing, C h i n a ) , PM Technology, Vol 11, No 3, 1993, 196-201. (In Chinese). A study of W alloys with a d d i t i o n s of rare e a r t h e l e m e n t s is reported. The alloys are used as electrodes. The a d d i t i o n of Y as oxide is s h o w n to be t h e m o s t beneficial due to t h e grain refining effects. Effects of oxides of W were also investigated.

Ceramic materials OPTIMIZATION OF SINTERING OF CERAMICS

V.M. Gropyanov, ~ L . Rizhikov (Technological Inst., St Petersburg, Russia), Science ofSintering, Vol 25, No 3, 1993, 109-116. The sintering of ceramics was discussed with respect to strength, wear and characteristics of grain size a n d porosity developed during sintering. The problem of o p t i m i z a t i o n of sintering is considered. The kinetics of densification were d e t e r m i n e d e x p e r i m e n t a l l y a n d used to optimize time a n d t e m p e r a t u r e conditions for s i n t e r e d Al2Oa.

Electrical and magnetic materials S I N T E R E D NICKEL-COPPER-ZINC POWDER F E R R I T E S FOR COMPOSITE CHIP COMPONENTS

S. Saito et al (TDK Corp, Narita, J a p a n ) , J. Japan Soc. Powder and Powder Metallurgy, Vol 40, No 8, 1993, 809-814. (In Japanese). The effects of c o m p o s i t i o n , r e s i d u a l stresses, a n d small a m o u n t s of additives on t h e electromagnetic p r o p e r t i e s of Ni-CuZn f e r r i t e s w e r e i n v e s t i g a t e d . It w a s r e p o r t e d t h a t electrical loss is strongly d e p e n d e n t on composition which m u s t be

strictly controlled. I n c r e a s e in r e s i d u a l stress increases hysteresis loss. V205 is shown to be t h e m o s t effective additive.

H a r d m a t e r i a l s a n d tool steels PHASE COMPOSITION IN C E M E N T E D CARBIDES AND C E R M E T S

P. Lindahl et al (Chalmers University of Technology, GSteborg, Sweden), Int. J. Refractory Metals & Hard Materials, Vol 12, No 3, 1993-1994, 107-113. An investigation of p h a s e c o m p o s i t i o n in a range of c e m e n t e d carbides is described. All were r e p o r t e d to consist of a skeleton of hard phases with grain boundary segregation of binder. Some of t h e m e t a l from t h e h a r d p h a s e was detected in t h e b i n d e r b u t very little C or N. C o r e / r i m s t r u c t u r e s were found in cermets with more t h a n one h a r d phase. ANALYSIS OF B I N D E R P H A S E S IN TITANIUM-MOLYBDENUM HARD METAL C E R M E T S

P. Lindahl et al ( C h a l m e r s University of Technology, GSteborg, S w e d e n ) , Int. J. Refractory Metals & Hard Materials, Vol 12, No 3, 1993-1994, 115-119. The compositions of t h e b i n d e r p h a s e s in a series of cermets b a s e d on TiC-TiNMoC2-(Co/Ni) were investigated by a t o m p r o b e field ion microscopy. A range of Co:Ni ratios were tested. The c o n c e n t r a t i o n of Mo in t h e b i n d e r increases with increase in %TiN a n d with increasing Co:Ni ratio. Ti decreases with %TIN. C o n c e n t r a t i o n of W a n d N in t h e b i n d e r is very small. Increase in TiN reduce t h e a m o u n t of N in t h e binder. MOLAR VOLUMES AND VOLUME FRACTIONS OF P H A S E S IN TUNGSTENCARBON-COBALT C E M E N T E D CARBIDES

B. U h r e n i u s ( S w e d i s h Inst. of M e t a l s Research, Stockholm, Sweden), Inst. J. Refractory Metals & Hard Materials, Vol 12, No 3, 1993-1994, 121-127. T h e r m o d y n a m i c s is applied to densities a n d lattice p a r a m e t e r s of p h a s e s in t h e WC-Co system, composition a n d t e m p e r a t u r e being t a k e n into account. The resulting p a r a m e t e r s are used to show how volume fractions vary with temperature and composition. It is s h o w n t h a t t h e d a t a can be used to predict volume changes d u r i n g cooling a n d t h e r m a l expansion. Predicted a n d e x p e r i m e n t a l d a t a are compared. INFLUENCE OF P R E S S U R E S I N T E R I N G ON P R O P E R T I E S OF C E M E N T E D CARBIDES

A. Doubravsky, P. Vasak (VUPM, Sumperk, Czechoslovakia), Pokroky Psaskove Metalurgie, No 4, 1993, 5-16. (In Czech).

PM

An investigation of pressure sintering (HIP) on t h e p r o p e r t i e s of c e m e n t e d carbides is described. A c o m p a r i s o n is made between the properties of conventionally sintered and pressure sintered materials. F R A C T U R E T O U G H N E S S O F TWOPHASE TUNGSTEN CARBIDE-COBALT CERMETS

K.S. Ravichandran (Wright Patterson Air Force Base, Ohio, USA), A c t a Metall, Mater., Vol 42, No 1, 1994, 143-150. The fracture toughness of WC-Co was discussed with regard to prediction from fracture mechanism relationships. Resistance to f r a c t u r e is a t t r i b u t e d to plastic deformation of the Co matrix. It is a s s u m e d t h a t deformation of Co between the WC particles a p p r o x i m a t e s to ideal plastic flow of a ductile layer between rigid platens and this was incorporated in the fracture toughness predictions. Reasonable agreement between predicted and m e a s u r e d values of fracture t o u g h n e s s is reported. I N V E S T I G A T I O N OF D I R E C T S I N T E R I N G FOR P R O D U C T I O N OF T15 HIGH SPEED STEEL

J M . Gallardo, E.J. H e r r e r a (E.T.S. de I n g e n i e r o s I n d u s t r i a l e s , Seville, S p a i n ) , Rev. de Metall., Vol 29, No 6, 1993, 362367. (In Spanish). A study of the process variables affecting the production of T15 HSS is described. Processing was cold compaction and direct sintering. Emphasis is p l a c e d o n compaction pressure, bulk lubrication with graphite and die wall lubrication with Zn stearate and green strength and density of compacts. E L E C T R O N M I C R O S C O P E S T U D Y OF STEEL BONDED CEMENTED CARBIDE

W. Qiang et al (Hua Zhong University of Science and Technology, Wuhuan, China), P M Technology, Vol 11, No 3, 1993, 202207. Transmission microscopy studies of TiC 50Nb Steel bonded c e m e n t e d carbides is described. Structure is shown to influence p r o p e r t i e s due to t h e p r e c i p i t a t i o n of carbides in the steel matrix.

Mechanical alloying M E C H A N I C A L ALLOYING OF IRONS I L I C O N P O W D E R S A N D E F F E C T S OF HEAT TREATMENT

S.Shiga et al (Nihama College of Technology, Nihama, J a p a n ) , J. J a p a n Soc. P o w d e r a n d P o w d e r M e t a l l u r g y , Vol 40, No 8, 1993, 770-773. (In J a p a n e s e ) . An investigation of MA of Si-(10 to 50) at%Fe is described. The MA powders were

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characterized. It is r e p o r t e d t h a t ~FeSi is formed in Si-50at%Fe and [3FeSi2 in Si30%Fe. Equilibrium p h a s e s were formed on heating in the range 900 to 1000°C and air cooled.

pM2TEC'94. The abstracts which follow are for papers which were presented at the international Conference on P o w d e r Metallurgy and Particulate Materials which was held in T o r o n t o , C a n a d a from 8th to l lth M a y 1994.

Powder production I M P R O V E M E N T S ON A T O M I Z E D POWDERS THROUGH ORIENTED P R O B L E M SOLVING

D.J. K a s p u t i s et al ( H o e g a n a e s Corp, Riverton, New Jersey, USA). The total quality of the system in use for p r o d u c t i o n of a t o m i z e d p o w d e r s w a s described. The i m p o r t a n c e of employee participation was emphasized. The p h a s e s of t h e o p e r a t i o n s , p r o d u c t c o n t r o l , statistics, documentation, personal development and process development w e r e c o n s i d e r e d . I m p r o v e m e n t in t h e microcleanliness of powders was used as an example. OXYGEN IN I R O N A N D S T E E L POWDERS

S.M. Kaufman (Peerless Metal Powders and Abrasives, USA). An investigation of the chemistry and stability of the oxides formed in Fe and steel powder during processing was described, it was r e p o r t e d t h a t additions of elements such as Si or A1 increased the stability of the oxides but t h a t the oxide of Si may be reduced in presence of enough C. Thermodynamics was used to justify the conclusion. MICROSTRUCTURAL DEVELOPMENT IN P O W D E R A T O M I Z A T I O N

W.J. Boettinger (NIST, USA). Microstructural evolution during atomization to powder was discussed with regard to nucleation, freezing rate and motion of the liquid/solid interface. An e x p e r i m e n t a l study of A1-8wt%Fe alloys was described in which distinct microstructures were observed according to particle sizes. In the finest powder, 10 prom, with a large d e g r e e of u n d e r c o o l i n g , a two z o n e structure of coarse and fine ~ cells was found. As particle size increased structures of ~kl and ~AI/FeAI3 with eutectic were formed. In particles above 40 p m m proeutectic FeAl~ was present.

Compaction DENSITY DISTRIBUTION AND MAGNETIC FLUX DURING C O M P A C T I O N IN M A G N E T I C F I E L D H. Kotera, S. Shima (Kyoto University, Kyoto, J a p a n ) . The compaction of magnetic materials in a m a g n e t i c field was reviewed w i t h r e s p e c t to p r o d u c t a n d p r o c e s s i m p r o v e m e n t s , m o v e m e n t s of p a r t i c l e s in the applied field, effects at the diewall a n d d e n s i t y d i s t r i b u t i o n s . F i n i t e element analysis was applied 1,o density distribution to determine tile relationships between powder/die-wall interactions, density and magnetic flux. Effects of m a g n e t i c flux on i n t e r n a l s t r e s s e s in c o m p a c t s d u r i n g c o n s o l i d a t i o n were discussed. N E W E X T R U S I O N M E T H O D FOR C O N S O L I D A T I O N OF P O W D E R S

H. Hoshino, S. Kohara (Science University of Tokyo, J a p a n ) . The use of extrusion for the c o n s o l i d a t i o n of metal p o w d e r s was discussed. It was noted t h a t there may be considerable residual porosity which has a d e t r i m e n t a l effect on properties. A m o d i f i e d e x t r u s i o n t e c h n i q u e , which was reported to result in lower porosity, by giving larger s h e a r deformation, was described. The p o w d e r was c o m p r e s s e d i n t o a c y l i n d e r and t h e n e x t r u d e d at r i g h t a n g l e s to t h e a x i s of t h e f i r s t c o m p r e s s i o n . It w a s r e p o r t e d t h a t densities of 98 to 99% were a t t a i n e d and a t e n s i l e s t r e n g t h of 120 MPa for AI deformed 30% in extrusion. N E T S H A P E F O R G I N G OF H I P IMPLANT COMPONENTS

R.V. Raman, S.V. Rele (Ceracon Inc, Scaramento, California, USA). The manufacture of femoral stems and h e a d s for hip p r o s t h e s e s was discussed with reference to forging. It was suggested that production from metal powder may offer a lower cost m e t h o d d e p e n d e n t on the attainment of satisfactory p r o p e r t i e s . An i n v e s t i g a t i o n , w h i c h considered net s h a p e forming, evaluation of m e c h a n i c a l p r o p e r t i e s a n d w e a r , was described. Dimensional control was analyzed. M A N U F A C T U R E OF H I G H P E R F O R M A N C E S I N T E R E D S T E E L S BY A DOUBLE PRESS/DOUBLE SINTER ROUTE

I.W. Donaldson, R.R. Biederman (The Presmet Corp, Worcester, USA). It was r e p o r t e d t h a t a double p r e s s / double sinter route had been used to p r o c e s s f e r r o u s m a t e r i a l s to h i g h d e n s i t y a n d high levels of m e c h a n i c a l

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