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Heat treatment of PM parts - mechanical properties and tolerance
e n a b l e easy control of t h e W skeleton, to e n h a n c e Cu infiltration a n d to stabilize t h e microstructure. E N H A N C E D SINTERING OF MICROHOMOGENEOUS TUNGSTENCOPPER COMPOSITE POWDER
J.S. Lee et al. (Hanyang University, Ansan, Korea). It was r e p o r t e d t h a t t h e sintering of W20wt% Cu powders could be e n h a n c e d by t h e t h o r o u g h mixing of t h e Cu a n d W p o w d e r s by h i g h e n e r g y b a l l m i l l i n g followed by H reduction. Investigations in which green compacts with a green density of 60% were sintered in H a t t e m p e r a t u r e s u p to 1400°C were described. It was found t h a t full d e n s i t y could be a t t a i n e d a t 1200°C. T h e e n h a n c e d s i n t e r i n g w a s d i s c u s s e d w i t h c o n s i d e r a t i o n given to m i c r o s t r u c t u r a l evolution. SINTERING S T U D I E S ON T U N G S T E N CARBIDE-COBALT HARDMETALS
L Prakash, H. Westermann. (United Hardm e t a l GmbH, Horb, Germany). Sintering of WC-Co was investigated with reference to t h e effects of carbide grain size, 0.8, 1.0 a n d 3 ~tm a n d t h e a d d i t i o n of VC, Cr2C3 a n d TabNbC. It was considered t h a t m o s t of t h e sintering takes place in t h e solid s t a t e even t h o u g h WC-Co is r e g a r d e d as a liquid p h a s e sintering system. Control of t h e solid s t a t e sintering was said to be essential for control of m i c r o s t r u c t u r e a n d h e n c e for optimization of the production of high integrity c e m e n t e d carbide parts. THE ROLE OF B I N D E R MELTING A N D CRYSTALLIZATION ON STRUCTURE DEVELOPMENT IN HARD METALS
K.S. C h e r n i a v s k y et al (Refractory a n d H a r d m e t a l s Research Institute, Moscow, Russia). Structural evolution d u r i n g sintering of WC-Co a n d W-Ni-Fe was investigated, pore s h a p e a n d grain growth being studied. In WC-Co t h e d o m i n a n t m e c h a n i s m s before melting of t h e b i n d e r were recrystallization of Co a n d p r e c i p i t a t i o n . In W-Ni-Fe i n d e p e n d e n t nucleation of W was possible. Differences in s t r u c t u r e d e v e l o p m e n t were attributed to differences in crystal anisotropy a n d WC/Co a n d W/Fe-Ni p h a s e b o u n d a r y energies.
Liquid phase sintering SIMULATION OF SOLUTION REPRECIPITATION P R O C E S S
Z.S. Nikolic, M.M. Ristic, (Serbian Academy of Sciences a n d Arts, Belgrade, Serbia). E x p e r i m e n t a l results were used to show t h a t t h e driving force for t h e solutionr e p r e c i p i t a t i o n p r o c e s s is t h e c h e m i c a l potential between solid grains and
42 MPR January 1994
solid alloy. A c o m p u t e r simulation of t h e p r o c e s s was p r e s e n t e d . The t h e o r e t i c a l basis of t h e s i m u l a t i o n was given a n d it was suggested t h a t t h e simulation was general and applicable to any twoc o m p o n e n t system. E F F E C T OF MECHANICAL GRINDING ON LIQUID PHASE SINTERING OF COPPER-LEAD ALLOYS
T. O h a s h i e t al ( N a g o y a I n s t i t u t e of Technology, Nagoya, J a p a n ) . A c o m p a r i s o n was m a d e of t h e sintering of C u - P b c o m p a c t s m a d e f r o m w a t e r a t o m i z e d p o w d e r or from m e c h a n i c a l l y ground powders using dilatometry and m e t a l l o g r a p h y . E x p a n s i o n s were n o t e d a t t h e melting p o i n t of Pb a n d a t 627 to 727°C according to time of grinding which w a s a t t r i b u t e d to r e c r y s t a l l i z a t i o n of t h e Cu.
Novel surface treatments HEAT TREATMENT OF PM PARTS -MECHANICAL P R O P E R T I E S AND TOLERANCES W. Z i m m e r m a n n , (Ringsdorff-Werke GmbH, Bonn, Germany). Heat t r e a t m e n t processes, carburizing, nitriding, carbonitriding and through hardening, used to e n h a n c e t h e p r o p e r t i e s o f PM s t e e l s , w e r e r e v i e w e d and characteristic dimensional and property changes were given. It was suggested t h a t through hardening enabled closer dimensional tolerances and higher t o u g h n e s s to be attained. Carburizing can b e u s e d to i m p r o v e w e a r a n d fatigue properties and nitriding for more specialized applications. TECHNOLOGY AND APPLICATIONS OF CHEMICALLY VAPOUR D E P O S I T E D DIAMOND FILMS
N. Fujimori. ( S u m i t o m o Electric I n d u s t r i e s Ltd, Itami City, J a p a n ) . The technology a n d a p p l i c a t i o n of CVD d i a m o n d film were reviewed. D i a m o n d containing cutting tools were also discussed. F u t u r e t r e n d s were indicated a n d it was a n t i c i p a t e d t h a t CVD d i a m o n d s will find widespread a p p l i c a t i o n s in active a n d passive devices. INFLUENCE OF S I N T E R E D DENSITY ON THE MICROSTRUCTURE OF IONN I T R I D E D LAYERS ON S T E E L S
X. Su et al (Heat T r e a t m e n t Institute, Beijing, China). A study of p h a s e compositions in t h e n i t r i d e d layers on ion-nitrided PM steels, as a function of p h a s e composition in t h e nitrided layers on ion-nitrided PM steels, as a function of sintered density was described. It was s h o w n t h a t after ionnitriding a t 580°C t h e a m o u n t of 7 p h a s e
a n d t h e d e p t h of N p e n e t r a t i o n increased with t h e n u m b e r of pores. Structure a n d pore d i s t r i b u t i o n also influenced t h e d e p t h of p e n e t r a t i o n a n d p h a s e composition. DISTRIBUTION OF ALLOYING E L E M E N T S IN ION-NITRIDED S I N T E R E D CHROMIUM-MOLYBDENUM S T E E L
H. Yin et al (Powder Metallurgy Institute, Beijing, China). The d i s t r i b u t i o n of Cr a n d Mo in a sintered and ion-nitrided steel was investigated with reference to the discrepancy between N c o n c e n t r a t i o n n e a r pores a n d in t h e matrix. After nitriding a t 620°C for 4 h o u r s t h e Cr a n d Mo c o n t e n t s of t h e n i t r i d e d layer was 1.5 t i m e s t h a t of t h e matrix. The m e c h a n i s m s of Cr a n d Mo diffusion against the concentration g r a d i e n t was discussed. USE OF ELECTROSPARK ALLOYING FOR PRODUCTION OF WEAR R E S I S T A N T COATINGS
E~A. Levashov et al (Russia). The u s e of e l e c t r o s p a r k alloying to deposit a layer c o n t a i n i n g Ti, Cr a n d Ta carbides a n d ultrafine d i a m o n d particles was described. The process was shown to be p o s s i b l e d u e to self p r o p a g a t i o n h i g h temperature synthesis reactions. The f o r m a t i o n of t h e c o m p o n e n t s of t h e coatings a n d t h e coatings was discussed. GAS PHASE D E P O S I T I O N OF REFRACTORY METALS BY DECOMPOSITION OF F L U O R I D E S
Y.M. Korolev. (Refractory a n d H a r d m e t a l s Research Institute, Moscow, Russia). T h e p h y s i c o - c h e m i c a l p r i n c i p l e s of d e p o s i t i o n of W, Mo, Nb a n d Ta from gaseous fluorides were discussed. It was shown t h a t in t h e case W a n d Ta deposit is not affected by i n t e r m e d i a t e fluorides. I n t e r m e d i a t e fluorides influence deposits o f N b a n d Mo. T h e d e p o s i t s were d e s c r i b e d a n d c o n d i t i o n s of d e p o s i t i o n were given. COATINGS OF SILICON AND BORON CARBIDES FORMED BY INTERACTION WITH METAL POWDERS
E.Y. G u t m a n a s et al (Technion, Haifa, Israel). It was r e p o r t e d t h a t coatings on carbide particles h a d b e e n formed by reactions b e t w e e n SiC, BaC a n d g r a p h i t e a n d strongly carbide forming metals. The coatings were found to consist of carbides, silicides or borides. The t h e r m a l stability of t h e coatings was assessed by incorporating coated or u n c o a t e d powders in Ni or Fe base PM matrices a n d h e a t t r e a t m e n t a t 1000 to 1100°C. The coatings were shown to i m p r o v e t h e s t a b i l i t y of SiC, BaC a n d g r a p h i t e in m e t a l matrices.
J.S. Lee et al. (Hanyang University, Ansan, Korea). It was r e p o r t e d t h a t t h e sintering of W20wt% Cu powders could be e n h a n c e d by t h e t h o r o u g h mixing of t h e Cu a n d W p o w d e r s by h i g h e n e r g y b a l l m i l l i n g followed by H reduction. Investigations in which green compacts with a green density of 60% were sintered in H a t t e m p e r a t u r e s u p to 1400°C were described. It was found t h a t full d e n s i t y could be a t t a i n e d a t 1200°C. T h e e n h a n c e d s i n t e r i n g w a s d i s c u s s e d w i t h c o n s i d e r a t i o n given to m i c r o s t r u c t u r a l evolution. SINTERING S T U D I E S ON T U N G S T E N CARBIDE-COBALT HARDMETALS
L Prakash, H. Westermann. (United Hardm e t a l GmbH, Horb, Germany). Sintering of WC-Co was investigated with reference to t h e effects of carbide grain size, 0.8, 1.0 a n d 3 ~tm a n d t h e a d d i t i o n of VC, Cr2C3 a n d TabNbC. It was considered t h a t m o s t of t h e sintering takes place in t h e solid s t a t e even t h o u g h WC-Co is r e g a r d e d as a liquid p h a s e sintering system. Control of t h e solid s t a t e sintering was said to be essential for control of m i c r o s t r u c t u r e a n d h e n c e for optimization of the production of high integrity c e m e n t e d carbide parts. THE ROLE OF B I N D E R MELTING A N D CRYSTALLIZATION ON STRUCTURE DEVELOPMENT IN HARD METALS
K.S. C h e r n i a v s k y et al (Refractory a n d H a r d m e t a l s Research Institute, Moscow, Russia). Structural evolution d u r i n g sintering of WC-Co a n d W-Ni-Fe was investigated, pore s h a p e a n d grain growth being studied. In WC-Co t h e d o m i n a n t m e c h a n i s m s before melting of t h e b i n d e r were recrystallization of Co a n d p r e c i p i t a t i o n . In W-Ni-Fe i n d e p e n d e n t nucleation of W was possible. Differences in s t r u c t u r e d e v e l o p m e n t were attributed to differences in crystal anisotropy a n d WC/Co a n d W/Fe-Ni p h a s e b o u n d a r y energies.
Liquid phase sintering SIMULATION OF SOLUTION REPRECIPITATION P R O C E S S
Z.S. Nikolic, M.M. Ristic, (Serbian Academy of Sciences a n d Arts, Belgrade, Serbia). E x p e r i m e n t a l results were used to show t h a t t h e driving force for t h e solutionr e p r e c i p i t a t i o n p r o c e s s is t h e c h e m i c a l potential between solid grains and
42 MPR January 1994
solid alloy. A c o m p u t e r simulation of t h e p r o c e s s was p r e s e n t e d . The t h e o r e t i c a l basis of t h e s i m u l a t i o n was given a n d it was suggested t h a t t h e simulation was general and applicable to any twoc o m p o n e n t system. E F F E C T OF MECHANICAL GRINDING ON LIQUID PHASE SINTERING OF COPPER-LEAD ALLOYS
T. O h a s h i e t al ( N a g o y a I n s t i t u t e of Technology, Nagoya, J a p a n ) . A c o m p a r i s o n was m a d e of t h e sintering of C u - P b c o m p a c t s m a d e f r o m w a t e r a t o m i z e d p o w d e r or from m e c h a n i c a l l y ground powders using dilatometry and m e t a l l o g r a p h y . E x p a n s i o n s were n o t e d a t t h e melting p o i n t of Pb a n d a t 627 to 727°C according to time of grinding which w a s a t t r i b u t e d to r e c r y s t a l l i z a t i o n of t h e Cu.
Novel surface treatments HEAT TREATMENT OF PM PARTS -MECHANICAL P R O P E R T I E S AND TOLERANCES W. Z i m m e r m a n n , (Ringsdorff-Werke GmbH, Bonn, Germany). Heat t r e a t m e n t processes, carburizing, nitriding, carbonitriding and through hardening, used to e n h a n c e t h e p r o p e r t i e s o f PM s t e e l s , w e r e r e v i e w e d and characteristic dimensional and property changes were given. It was suggested t h a t through hardening enabled closer dimensional tolerances and higher t o u g h n e s s to be attained. Carburizing can b e u s e d to i m p r o v e w e a r a n d fatigue properties and nitriding for more specialized applications. TECHNOLOGY AND APPLICATIONS OF CHEMICALLY VAPOUR D E P O S I T E D DIAMOND FILMS
N. Fujimori. ( S u m i t o m o Electric I n d u s t r i e s Ltd, Itami City, J a p a n ) . The technology a n d a p p l i c a t i o n of CVD d i a m o n d film were reviewed. D i a m o n d containing cutting tools were also discussed. F u t u r e t r e n d s were indicated a n d it was a n t i c i p a t e d t h a t CVD d i a m o n d s will find widespread a p p l i c a t i o n s in active a n d passive devices. INFLUENCE OF S I N T E R E D DENSITY ON THE MICROSTRUCTURE OF IONN I T R I D E D LAYERS ON S T E E L S
X. Su et al (Heat T r e a t m e n t Institute, Beijing, China). A study of p h a s e compositions in t h e n i t r i d e d layers on ion-nitrided PM steels, as a function of p h a s e composition in t h e nitrided layers on ion-nitrided PM steels, as a function of sintered density was described. It was s h o w n t h a t after ionnitriding a t 580°C t h e a m o u n t of 7 p h a s e
a n d t h e d e p t h of N p e n e t r a t i o n increased with t h e n u m b e r of pores. Structure a n d pore d i s t r i b u t i o n also influenced t h e d e p t h of p e n e t r a t i o n a n d p h a s e composition. DISTRIBUTION OF ALLOYING E L E M E N T S IN ION-NITRIDED S I N T E R E D CHROMIUM-MOLYBDENUM S T E E L
H. Yin et al (Powder Metallurgy Institute, Beijing, China). The d i s t r i b u t i o n of Cr a n d Mo in a sintered and ion-nitrided steel was investigated with reference to the discrepancy between N c o n c e n t r a t i o n n e a r pores a n d in t h e matrix. After nitriding a t 620°C for 4 h o u r s t h e Cr a n d Mo c o n t e n t s of t h e n i t r i d e d layer was 1.5 t i m e s t h a t of t h e matrix. The m e c h a n i s m s of Cr a n d Mo diffusion against the concentration g r a d i e n t was discussed. USE OF ELECTROSPARK ALLOYING FOR PRODUCTION OF WEAR R E S I S T A N T COATINGS
E~A. Levashov et al (Russia). The u s e of e l e c t r o s p a r k alloying to deposit a layer c o n t a i n i n g Ti, Cr a n d Ta carbides a n d ultrafine d i a m o n d particles was described. The process was shown to be p o s s i b l e d u e to self p r o p a g a t i o n h i g h temperature synthesis reactions. The f o r m a t i o n of t h e c o m p o n e n t s of t h e coatings a n d t h e coatings was discussed. GAS PHASE D E P O S I T I O N OF REFRACTORY METALS BY DECOMPOSITION OF F L U O R I D E S
Y.M. Korolev. (Refractory a n d H a r d m e t a l s Research Institute, Moscow, Russia). T h e p h y s i c o - c h e m i c a l p r i n c i p l e s of d e p o s i t i o n of W, Mo, Nb a n d Ta from gaseous fluorides were discussed. It was shown t h a t in t h e case W a n d Ta deposit is not affected by i n t e r m e d i a t e fluorides. I n t e r m e d i a t e fluorides influence deposits o f N b a n d Mo. T h e d e p o s i t s were d e s c r i b e d a n d c o n d i t i o n s of d e p o s i t i o n were given. COATINGS OF SILICON AND BORON CARBIDES FORMED BY INTERACTION WITH METAL POWDERS
E.Y. G u t m a n a s et al (Technion, Haifa, Israel). It was r e p o r t e d t h a t coatings on carbide particles h a d b e e n formed by reactions b e t w e e n SiC, BaC a n d g r a p h i t e a n d strongly carbide forming metals. The coatings were found to consist of carbides, silicides or borides. The t h e r m a l stability of t h e coatings was assessed by incorporating coated or u n c o a t e d powders in Ni or Fe base PM matrices a n d h e a t t r e a t m e n t a t 1000 to 1100°C. The coatings were shown to i m p r o v e t h e s t a b i l i t y of SiC, BaC a n d g r a p h i t e in m e t a l matrices.