- Email: [email protected]
Int J refractory metals & hard materials
PM
P o w d e r production POWDERS FROM METAL MELTS BY USE OF S U P E R S O N I C LAMINAR GAS STREAMS L. Gerking ( N a n o v a l E n t w i c k l u n g s KG, Berlin, G e r m a n y ) Powder Metall Int, Vol 25, No 2, 1993, 59-65. A novel gas a t o m i z a t i o n p r o c e s s is described. Metal or ceramic melt s t r e a m s are drawn out by parallel gas flows, at high velocity, to a very small size followed by d i s i n t e g r a t i o n into globular particles. A n a r r o w range of particle sizes is r e p o r t e d a n d t h e process is more energy efficient. A m a t h e m a t i c a l description of t h e process is given. The process was used for m o l t e n materials up to 200°C.
PRODUCTS" Tungsten D E P L E T I O N OF IRIDIUM FROM TUNSTEN-IRIDIUM ALLOYS DURING WORK FUNCTION T E S T I N G L ~ D'Cruz, D.L. Jacobson, (Arizona State University, Tempe, USA,) Int, J. Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 223-234. A study of t h e role of Ir in modifying t h e work f u n c t i o n of W is described. The application considered is as a t h e r m i o n i c emitter for which a high work function is required a n d t h e alloys can be m a d e by PM or arc casting. A vacuum emission t e c h n i q u e was used a n d depletion of Ir was measured by electron probe microanalysis. Theoretical prediction of Ir s e g r e g a t i o n could n o t a c c o u n t for t h e a m o u n t of Ir depletion a n d a n alternative e x p l a n a t i o n is proposed. This involves t h e formation of Ir rich layers during h e a t t r e a t m e n t of t h e alloys prior to testing. E F F E C T S OF GRAIN SHAPE ON C R E E P RATES IN PM T U N G S T E N WIRE I~ Tanoue et al, J Japan Inst of Metals, Vol 57, No 1, 1993, 14-20. (In J a p a n e s e ) . Characteristics of secondary recrystallized grains in PM W wire are defined in t h r e e dimensions. The effects of h e a t i n g rates on grain s h a p e changes were investigated in n o n - d o p e d W wire a n d the defined parameters indicate t h r e e d i m e n s i o n a l changes. The effects of grain configuration on steady state creep were determined. It is r e p o r t e d t h a t t h e grain configuration can be used to s u p p r e s s creep only w h e n t h e grain boundary area is not substantially altered.
LITERATURE
REVIEW
Hard materials and tool steels ELECTRON MICROSCOPIC STUDY OF CORE-RIM S T R U C T U R E S IN TITANIUM CARBONITRIDE C E R M E T S T. Laoui et al (Katholic University, Leuven, Heverlee, Belgium, Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 207212. An investigation of core-rim s t r u c t u r e s in Ti (C,N) - 11.1 Wt%WC- 15.2%Mo2C-8.7%Co5.4%Ni Ti (C,N) - 18.2wt%WC- 13.5%TaC8.1%Co-7.8%Ni, using analytical electron microscopy, is described. It is r e p o r t e d that core and rim have the same structures in some grains a n d t h e r e are small differences in others. There is a small m i s o r i e n t a t i o n b e t w e e n core a n d r i m resulting in generation of dislocations a t t h e interface w h e n t h e lattice p a r a m e t e r s are the same. SILICON CARBIDE-SILCON NITRIDE C O M P O S I T E MATERIALS V. Biansini et al (Resaearc Inst, for Ceramic Technology, Faenza, Italy), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 213-221. It is r e p o r t e d t h a t SiaN4 20vol%SiC s u b m i c r o n p a r t i c l e reinforced m a t e r i a l s h a d been p r o d u c e d by hot pressing a n d pressureless sintering. The sintering characteristics were found to be influenced by t h e p r e s e n c e of t h e SiC particles. The mechanical properties were strongly d e p e n d e n t on grain size, a m o u n t of s i n t e r i n g aid a d d e d , d e n s i f i c a t i o n a n d particle reinforcement. ANALYTICAL TOOLS FOR THE CHARACTERIZATION OF C E R M E T S P. Wilhartitz et al (Metallwerk Plansee GmbH, Reutte, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 235-246. The literature concerning c h a r a c t e r i z a t i o n , by a w i d e r a n g e of methods, of cermets is critically reviewed. An i n v e s t i g a t i o n , in w h i c h t h e b i n d e r phases of cermets were chemically dissolved a n d t h e surface of t h e r e m a i n i n g carbides e x a m i n e d by analytical electron microscopy and three-dimensional s e c o n d a r y i o n m a s s s p e c t r o m e t r y , is described. 3-D SIMS was found to give a d e p t h resolution of 10 ~m. It is shown t h a t t h e m a i n d i s t r i b u t i o n of c o m p o n e n t s between b i n d e r a n d carbide grains can be investigated.
E F F E C T S OF MICROWAVE PLASMA D E P O S I T I O N P A R A M E T E R S ON FORMATION OF DIAMOND COATINGS ON SILICON ALUMINIUM OXYNITRIDE (SIAION) SUBSTRATES A~ Lindlbauer et al (Technical University, Vienna, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992,247258. It is r e p o r t e d t h a t d i a m o n d films h a d b e e n g r o w n on SiA1ON s u b s t r a t e s by chemical v a p o u r deposition form CH4-H2 gas m i x t u r e s w i t h effects of gas p r e s s u r e a n d composition, microwave power a n d s u b s t r a t e t e m p e r a t u r e being studied. At low CH4 c o n c e n t r a t i o n s t h e d i a m o n d crystals were characterised by (111) facets and (110) facets at higher CH4. Correlations between diamond morphology, growth rate, h o m o g e n e i t y of t h e deposit a n d size of t h e p l a s m a ball are given a n d discussed. IMPORTANCE OF S U B S T R A T E TEMPERATURE AND OTHER P A R A M E T E R S IN HOT FILAMENT DIAMOND SYNTHESIS R. H a u b n e r et al (Technical University, Vienna, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 259269. A n i n v e s t i g a t i o n of t h e e f f e c t s of substrate temperature and other p a r a m e t e r s on t h e deposition of diamond, by h o t filament chemical v a p o u r deposition, on to c e m e n t e d carbides is described. The p a r a m e t e r s investigated included f i l a m e n t / s u b s t r a t e separation, filament t e m p e r a t u r e , gas composition, (CH4-H2) pressure a n d flow rate. Factors d e t e r m i n i n g s u b s t r a t e t e m p e r a t u r e a n d d i a m o n d growth rate a n d morphology are outlined. It is shown t h a t lower substrate temperatures give improved d i a m o n d adhesion. P R O P E R T I E S OF LIQUID PHASE S I N T E R E D T I 5 A N D T42 HIGH S P E E D STEELS P.I~ Kar et al (Tata Steels, J a m s h e d p u r , India), Int J Powder Metallurgy, Vol 29,
No 2, 1993, 139-148. An investigation of liquid phase s i n t e r i n g of T15 a n d T42 h i g h s p e e d steels, formed from water atomized powders, is described. Effects of sintering temperatures and atmospheres were studied. The optimum sintering t e m p e r a t u r e s to give high density were 127°C for T I 5 a n d 1230°C for T42 b o t h in vacuum. T15 is s h o w n to have h i g h e r h a r d n e s s a n d transverse r u p t u r e s t r e n g t h
MPR December 1993 47
P o w d e r production POWDERS FROM METAL MELTS BY USE OF S U P E R S O N I C LAMINAR GAS STREAMS L. Gerking ( N a n o v a l E n t w i c k l u n g s KG, Berlin, G e r m a n y ) Powder Metall Int, Vol 25, No 2, 1993, 59-65. A novel gas a t o m i z a t i o n p r o c e s s is described. Metal or ceramic melt s t r e a m s are drawn out by parallel gas flows, at high velocity, to a very small size followed by d i s i n t e g r a t i o n into globular particles. A n a r r o w range of particle sizes is r e p o r t e d a n d t h e process is more energy efficient. A m a t h e m a t i c a l description of t h e process is given. The process was used for m o l t e n materials up to 200°C.
PRODUCTS" Tungsten D E P L E T I O N OF IRIDIUM FROM TUNSTEN-IRIDIUM ALLOYS DURING WORK FUNCTION T E S T I N G L ~ D'Cruz, D.L. Jacobson, (Arizona State University, Tempe, USA,) Int, J. Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 223-234. A study of t h e role of Ir in modifying t h e work f u n c t i o n of W is described. The application considered is as a t h e r m i o n i c emitter for which a high work function is required a n d t h e alloys can be m a d e by PM or arc casting. A vacuum emission t e c h n i q u e was used a n d depletion of Ir was measured by electron probe microanalysis. Theoretical prediction of Ir s e g r e g a t i o n could n o t a c c o u n t for t h e a m o u n t of Ir depletion a n d a n alternative e x p l a n a t i o n is proposed. This involves t h e formation of Ir rich layers during h e a t t r e a t m e n t of t h e alloys prior to testing. E F F E C T S OF GRAIN SHAPE ON C R E E P RATES IN PM T U N G S T E N WIRE I~ Tanoue et al, J Japan Inst of Metals, Vol 57, No 1, 1993, 14-20. (In J a p a n e s e ) . Characteristics of secondary recrystallized grains in PM W wire are defined in t h r e e dimensions. The effects of h e a t i n g rates on grain s h a p e changes were investigated in n o n - d o p e d W wire a n d the defined parameters indicate t h r e e d i m e n s i o n a l changes. The effects of grain configuration on steady state creep were determined. It is r e p o r t e d t h a t t h e grain configuration can be used to s u p p r e s s creep only w h e n t h e grain boundary area is not substantially altered.
LITERATURE
REVIEW
Hard materials and tool steels ELECTRON MICROSCOPIC STUDY OF CORE-RIM S T R U C T U R E S IN TITANIUM CARBONITRIDE C E R M E T S T. Laoui et al (Katholic University, Leuven, Heverlee, Belgium, Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 207212. An investigation of core-rim s t r u c t u r e s in Ti (C,N) - 11.1 Wt%WC- 15.2%Mo2C-8.7%Co5.4%Ni Ti (C,N) - 18.2wt%WC- 13.5%TaC8.1%Co-7.8%Ni, using analytical electron microscopy, is described. It is r e p o r t e d that core and rim have the same structures in some grains a n d t h e r e are small differences in others. There is a small m i s o r i e n t a t i o n b e t w e e n core a n d r i m resulting in generation of dislocations a t t h e interface w h e n t h e lattice p a r a m e t e r s are the same. SILICON CARBIDE-SILCON NITRIDE C O M P O S I T E MATERIALS V. Biansini et al (Resaearc Inst, for Ceramic Technology, Faenza, Italy), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 213-221. It is r e p o r t e d t h a t SiaN4 20vol%SiC s u b m i c r o n p a r t i c l e reinforced m a t e r i a l s h a d been p r o d u c e d by hot pressing a n d pressureless sintering. The sintering characteristics were found to be influenced by t h e p r e s e n c e of t h e SiC particles. The mechanical properties were strongly d e p e n d e n t on grain size, a m o u n t of s i n t e r i n g aid a d d e d , d e n s i f i c a t i o n a n d particle reinforcement. ANALYTICAL TOOLS FOR THE CHARACTERIZATION OF C E R M E T S P. Wilhartitz et al (Metallwerk Plansee GmbH, Reutte, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 235-246. The literature concerning c h a r a c t e r i z a t i o n , by a w i d e r a n g e of methods, of cermets is critically reviewed. An i n v e s t i g a t i o n , in w h i c h t h e b i n d e r phases of cermets were chemically dissolved a n d t h e surface of t h e r e m a i n i n g carbides e x a m i n e d by analytical electron microscopy and three-dimensional s e c o n d a r y i o n m a s s s p e c t r o m e t r y , is described. 3-D SIMS was found to give a d e p t h resolution of 10 ~m. It is shown t h a t t h e m a i n d i s t r i b u t i o n of c o m p o n e n t s between b i n d e r a n d carbide grains can be investigated.
E F F E C T S OF MICROWAVE PLASMA D E P O S I T I O N P A R A M E T E R S ON FORMATION OF DIAMOND COATINGS ON SILICON ALUMINIUM OXYNITRIDE (SIAION) SUBSTRATES A~ Lindlbauer et al (Technical University, Vienna, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992,247258. It is r e p o r t e d t h a t d i a m o n d films h a d b e e n g r o w n on SiA1ON s u b s t r a t e s by chemical v a p o u r deposition form CH4-H2 gas m i x t u r e s w i t h effects of gas p r e s s u r e a n d composition, microwave power a n d s u b s t r a t e t e m p e r a t u r e being studied. At low CH4 c o n c e n t r a t i o n s t h e d i a m o n d crystals were characterised by (111) facets and (110) facets at higher CH4. Correlations between diamond morphology, growth rate, h o m o g e n e i t y of t h e deposit a n d size of t h e p l a s m a ball are given a n d discussed. IMPORTANCE OF S U B S T R A T E TEMPERATURE AND OTHER P A R A M E T E R S IN HOT FILAMENT DIAMOND SYNTHESIS R. H a u b n e r et al (Technical University, Vienna, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 259269. A n i n v e s t i g a t i o n of t h e e f f e c t s of substrate temperature and other p a r a m e t e r s on t h e deposition of diamond, by h o t filament chemical v a p o u r deposition, on to c e m e n t e d carbides is described. The p a r a m e t e r s investigated included f i l a m e n t / s u b s t r a t e separation, filament t e m p e r a t u r e , gas composition, (CH4-H2) pressure a n d flow rate. Factors d e t e r m i n i n g s u b s t r a t e t e m p e r a t u r e a n d d i a m o n d growth rate a n d morphology are outlined. It is shown t h a t lower substrate temperatures give improved d i a m o n d adhesion. P R O P E R T I E S OF LIQUID PHASE S I N T E R E D T I 5 A N D T42 HIGH S P E E D STEELS P.I~ Kar et al (Tata Steels, J a m s h e d p u r , India), Int J Powder Metallurgy, Vol 29,
No 2, 1993, 139-148. An investigation of liquid phase s i n t e r i n g of T15 a n d T42 h i g h s p e e d steels, formed from water atomized powders, is described. Effects of sintering temperatures and atmospheres were studied. The optimum sintering t e m p e r a t u r e s to give high density were 127°C for T I 5 a n d 1230°C for T42 b o t h in vacuum. T15 is s h o w n to have h i g h e r h a r d n e s s a n d transverse r u p t u r e s t r e n g t h
MPR December 1993 47