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Mechanical properties of silicon carbide-βsialon composites at high temperatures
PM CONSOLIDATION DYNAMICS OF T U N G S T E N POWDER DURING DRY BAG COLD ISOSTATIC P R E S S I N G
B.P. Bewlay, (GEC, Schenectady, New York, USA), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 165-174. The p a p e r describes t h e consolidation dynamics of W powder during CIP in t h e range 14 to 211 MPa pressurized at 2 or 10 MPa/sec. Elastic relaxation during depressurization is discussed in relation to origins of defects. Elastic r e l a x a t i o n was found to increase from 0.13% a t 14 MPa to 0.55% at 211 MPa. Heating of t h e c o m p a c t s was observed a n d t h i s is a t t r i b u t e d to interparticle friction a rise in t e m p e r a t u r e of a b o u t 10°C being found. The effect of pressurisation rate on h e a t generation is described.
Ceramics PHASE AND CHEMICAL C H A N G E S DURING OF PARTIALLY STABILIZED ZIRCONIA
M.I. Kabanova a n d V.A. D u b a k Poroshkovaya Metallurgiya, No 5, 1992, 85-89. (In Russian). C h a n g e s in t h e s u r f a c e p h a s e a n d chemical composition of ZrO2, m a d e from powders of differing structures, during air or v a c u u m s i n t e r i n g are described. An impirical formula for calculation of t h e p r o p o r t i o n of a non-equilibrium t e t r a g o n a l p h a s e is given. POSSIBILITIES FOR THE IMPROVEMENT OF RELIABILITY OF ADVANCED STRUCTURAL CERAMICS
J. Dusza, ( I n s t of M a t e r i a l s Research, Kosice, C z e c h o s l o v a k i a ) , Pokroky Psaskove Metalurgie, No 1, 1993, 23071. P o s s i b l e i m p r o v e m e n t s in t h e h i g h t e m p e r a t u r e p r o p e r t i e s of s t r u c t u r a l c e r a m i c m a t e r i a l s , i n c l u d i n g WC-Co, Al203-Siw, A1203-ZrO 2 a n d Si3N4-Si3N4w are discussed with reference to defects, pores a n d clusters of s t r u c t u r a l constituents, a n d s t r e n g t h e n i n g mechanisms. It is suggested t h a t i m p r o v e m e n t s in properties will accrue f r o m i m p r o v e d u n d e r s t a n d i n g of t h e i n f l u e n c e of m i c r o s t r u c t u r e o n c r e e p deformation and crack initiation and growth.
Composites MECHANICAL PROPERTIES OF SILICON CARBIDE-~SIALON COMPOSITES AT HIGH TEMPERATURES
C. Yamagashi et al (Nihon C e m e n t Co. Ltd., Tokyo, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 12, 1992, 1113-1118. (In J a p a n e s e ) . The high temperature mechanical p r o p e r t y / s t r u c t u r e r e l a t i o n s h i p s of SiC-
46 MPR July\August 1993
LITERATURE
REVIEW
~sialon composites were investigated. The a d d i t i o n of SiC is r e p o r t e d to increase t h e flexural s t r e n g t h a n d creep resistance of ~sialon. This is a t t r i b u t e d to less liquid phase formation being formed during sintering a n d improved creep resistance to inhibition of grain b o u n d a r y glide. THERMAL CONDUCTIVITIES OF COMPOSITES WITH U L T R A D I S P E R S E D TITANIUM NITRIDE-ALUMINIUM NITRIDE
O.L. Dozhdikova et al, Poroshkovaya Metallurgiya, No 5, 1992, 70-74. (In Russian). An investigation of the thermal properties, h e a t capacity a n d conductivity of A1N-TiN, in t h e r a n g e 20 to 1000°C, is described. The t h e r m a l c o n d u c t i v i t y of m a t e r i a l s m a d e from ultrafine powder is r e p o r t e d to b e 50% h i g h e r t h a n t h e calculated value for a m e c h a n i c a l mixture. It is suggested t h a t t h e TiN-AIN system could be used in t h e creation of new h e a t r e s i s t a n t materials.
Electrical and magnetic HIGH PERMEABILITY FERRITE
J. Miklik a n d J. P e t r e k ( P r a m e t a.s., Sumperk, Czechoslovakia), Pokroky Psaskove Metalurgie, No 1, 1993, 5-11. (In Czech). The p r o d u c t i o n of ferrite m a t e r i a l s by PM is r e p o r t e d to have been e x t e n d e d to t h e m a n u f a c t u r e of h i g h p e r m e a b i l i t y ferrites. The technical characteristics are described a n d p o t e n t i a l applications are discussed. MAGNETIC P R O P E R T I E S OF RAPIDLY SOLIDIFIED POWDERS HOT P R E S S E D AND DIE U P S E T IRON-NEODYMIUMBORON MAGNET ALLOYS
C-J. Choi et al (Korea Inst. of Machinery a n d Metals, Changwon, Korea), J Korean Inst of Metals, Vol 30, No 10, 1992, 12111217. (In Korean). An investigation of the magnetic properties of Fe-Nd-B alloys, in RS p o w d e r form, h o t pressed a n d die u p s e t conditions, is described. Hot pressing above 720°C is r e p o r t e d to yield fully d e n s e i s o t r o p i c m a t e r i a l s a n d h o t pressing a t 750°C to result in o p t i m u m properties. The d u r a t i o n of hot pressing is said to have little effect a n i s t r o p y was f o u n d in t h e die u p s e t materials due to a l i g n m e n t of t h e C-axis of t h e Fe14Nd2B parallel to t h e direction of upsetting.
Hard materials BRAZING OF C E M E N T E D TITANIUM CARBIDE TO STAINLESS S T E E L
W.C. Lee et al (Seoul National University, Seoul, Korea), J Korean Inst of Metals, Vol 30, No 9, 1992, 1136-1143. (In Korean).
An i n v e s t i g a t i o n of t h e s t r e n g t h of brazed j o i n t s between TiC-Co a n d 304L stainless steel is described. Low Ag brazing alloys were used a n d t h e effects of brazing alloy a n d conditions on s t r u c t u r e s a n d t h e s t r e n g t h of t h e interface were determined. J o i n t s t r e n g t h was assessed by a s h e a r test. Values u p to 257 MPa are reported. The s t r e n g t h of t h e b o n d is a t t r i b u t e d to t h e f o r m a t i o n of a Fe-Co-Ni-Cr alloy p r o d u c t a t t h e interface, t h e m e c h a n i s m s is described as a solid solution f o r m a t i o n between Co a n d Ni from t h e c e m e n t e d carbide a n d Fe, Ni a n d Cr from t h e stainless steel. PREPARATION OF A NICKELCHROMIUM OVERLAY WELD ALLOY CONTAINING FINELY D I S P E R S E D NIOBIUM CARBIDE PARTICLES
T. Tomita et al (Hyogo Inst of I n d u s t r i a l Research, Hyogo, J a p a n ) , J Japan Inst of Metals, Vol 56, No 11, 1992, 1296-1302. (In J a p a n e s e ) . The p r o d u c t i o n of a Ni-20 wt% Cr p o w d e r , 10 p m in size, c o n t a i n i n g a dispersion of a 1.3 p m NbC, using mixing a n d g r a n u l a t i o n of t h e p o w d e r s , is described. The powders are applied to a s u b s t r a t e by a p l a s m a arc process w h i c h m e l t s b o t h c o n s t i t u e n t s of t h e m i x e d powders. The objective of t h e work was to produce a hard, wear and corrosion r e s i s t a n t surface. MECHANICAL T E S T DISCRIMINABILITY FOR T U N G S T E N CARBIDE HARD METALS
B. Roebuck a n d W. Coles (National Physical Laboratory, Teddington, UK), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 127-136. The a b i l i t y of m e c h a n i c a l t e s t s to d i s c r i m i n a t e between m a t e r i a l s differing by small a m o u n t s is discussed. In order to t e s t t h i s two WC-6% Co alloys w e r e p r e p a r e d f r o m p o w d e r s differing by a small a m o u n t in particle size distribution. One specimen showed a uniform d i s t r i b u t i o n of Co a n d WC a n d o t h e r c o n t a i n e d small Co-rich regions several m i c r o n s in size. The h a r d n e s s , n o t c h e d and unnotched bend strengths, plane s t r a i n a n d i n d e n t a t i o n fracture t o u g h n e s s and abrasive wear resistance were compared. The t e s t s used are described in detail. Only t h e n o t c h e d b e n d a n d abrasive w e a r t e s t s showed differences between t h e two materials. NICKEL IN HARDMETALS
V.A. Tracey (Solihull, UK), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 137-149. A review of t h e literature concerning Ni in h a r d m e t a l s a n d cermets is presented. It is shown t h a t Ni can replace, wholly or partly, Co in WC-Co a n d in TiC b a s e m a t e r i a l s , for c u t t i n g t o o l a n d w e a r r e s i s t a n t applications.
B.P. Bewlay, (GEC, Schenectady, New York, USA), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 165-174. The p a p e r describes t h e consolidation dynamics of W powder during CIP in t h e range 14 to 211 MPa pressurized at 2 or 10 MPa/sec. Elastic relaxation during depressurization is discussed in relation to origins of defects. Elastic r e l a x a t i o n was found to increase from 0.13% a t 14 MPa to 0.55% at 211 MPa. Heating of t h e c o m p a c t s was observed a n d t h i s is a t t r i b u t e d to interparticle friction a rise in t e m p e r a t u r e of a b o u t 10°C being found. The effect of pressurisation rate on h e a t generation is described.
Ceramics PHASE AND CHEMICAL C H A N G E S DURING OF PARTIALLY STABILIZED ZIRCONIA
M.I. Kabanova a n d V.A. D u b a k Poroshkovaya Metallurgiya, No 5, 1992, 85-89. (In Russian). C h a n g e s in t h e s u r f a c e p h a s e a n d chemical composition of ZrO2, m a d e from powders of differing structures, during air or v a c u u m s i n t e r i n g are described. An impirical formula for calculation of t h e p r o p o r t i o n of a non-equilibrium t e t r a g o n a l p h a s e is given. POSSIBILITIES FOR THE IMPROVEMENT OF RELIABILITY OF ADVANCED STRUCTURAL CERAMICS
J. Dusza, ( I n s t of M a t e r i a l s Research, Kosice, C z e c h o s l o v a k i a ) , Pokroky Psaskove Metalurgie, No 1, 1993, 23071. P o s s i b l e i m p r o v e m e n t s in t h e h i g h t e m p e r a t u r e p r o p e r t i e s of s t r u c t u r a l c e r a m i c m a t e r i a l s , i n c l u d i n g WC-Co, Al203-Siw, A1203-ZrO 2 a n d Si3N4-Si3N4w are discussed with reference to defects, pores a n d clusters of s t r u c t u r a l constituents, a n d s t r e n g t h e n i n g mechanisms. It is suggested t h a t i m p r o v e m e n t s in properties will accrue f r o m i m p r o v e d u n d e r s t a n d i n g of t h e i n f l u e n c e of m i c r o s t r u c t u r e o n c r e e p deformation and crack initiation and growth.
Composites MECHANICAL PROPERTIES OF SILICON CARBIDE-~SIALON COMPOSITES AT HIGH TEMPERATURES
C. Yamagashi et al (Nihon C e m e n t Co. Ltd., Tokyo, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 12, 1992, 1113-1118. (In J a p a n e s e ) . The high temperature mechanical p r o p e r t y / s t r u c t u r e r e l a t i o n s h i p s of SiC-
46 MPR July\August 1993
LITERATURE
REVIEW
~sialon composites were investigated. The a d d i t i o n of SiC is r e p o r t e d to increase t h e flexural s t r e n g t h a n d creep resistance of ~sialon. This is a t t r i b u t e d to less liquid phase formation being formed during sintering a n d improved creep resistance to inhibition of grain b o u n d a r y glide. THERMAL CONDUCTIVITIES OF COMPOSITES WITH U L T R A D I S P E R S E D TITANIUM NITRIDE-ALUMINIUM NITRIDE
O.L. Dozhdikova et al, Poroshkovaya Metallurgiya, No 5, 1992, 70-74. (In Russian). An investigation of the thermal properties, h e a t capacity a n d conductivity of A1N-TiN, in t h e r a n g e 20 to 1000°C, is described. The t h e r m a l c o n d u c t i v i t y of m a t e r i a l s m a d e from ultrafine powder is r e p o r t e d to b e 50% h i g h e r t h a n t h e calculated value for a m e c h a n i c a l mixture. It is suggested t h a t t h e TiN-AIN system could be used in t h e creation of new h e a t r e s i s t a n t materials.
Electrical and magnetic HIGH PERMEABILITY FERRITE
J. Miklik a n d J. P e t r e k ( P r a m e t a.s., Sumperk, Czechoslovakia), Pokroky Psaskove Metalurgie, No 1, 1993, 5-11. (In Czech). The p r o d u c t i o n of ferrite m a t e r i a l s by PM is r e p o r t e d to have been e x t e n d e d to t h e m a n u f a c t u r e of h i g h p e r m e a b i l i t y ferrites. The technical characteristics are described a n d p o t e n t i a l applications are discussed. MAGNETIC P R O P E R T I E S OF RAPIDLY SOLIDIFIED POWDERS HOT P R E S S E D AND DIE U P S E T IRON-NEODYMIUMBORON MAGNET ALLOYS
C-J. Choi et al (Korea Inst. of Machinery a n d Metals, Changwon, Korea), J Korean Inst of Metals, Vol 30, No 10, 1992, 12111217. (In Korean). An investigation of the magnetic properties of Fe-Nd-B alloys, in RS p o w d e r form, h o t pressed a n d die u p s e t conditions, is described. Hot pressing above 720°C is r e p o r t e d to yield fully d e n s e i s o t r o p i c m a t e r i a l s a n d h o t pressing a t 750°C to result in o p t i m u m properties. The d u r a t i o n of hot pressing is said to have little effect a n i s t r o p y was f o u n d in t h e die u p s e t materials due to a l i g n m e n t of t h e C-axis of t h e Fe14Nd2B parallel to t h e direction of upsetting.
Hard materials BRAZING OF C E M E N T E D TITANIUM CARBIDE TO STAINLESS S T E E L
W.C. Lee et al (Seoul National University, Seoul, Korea), J Korean Inst of Metals, Vol 30, No 9, 1992, 1136-1143. (In Korean).
An i n v e s t i g a t i o n of t h e s t r e n g t h of brazed j o i n t s between TiC-Co a n d 304L stainless steel is described. Low Ag brazing alloys were used a n d t h e effects of brazing alloy a n d conditions on s t r u c t u r e s a n d t h e s t r e n g t h of t h e interface were determined. J o i n t s t r e n g t h was assessed by a s h e a r test. Values u p to 257 MPa are reported. The s t r e n g t h of t h e b o n d is a t t r i b u t e d to t h e f o r m a t i o n of a Fe-Co-Ni-Cr alloy p r o d u c t a t t h e interface, t h e m e c h a n i s m s is described as a solid solution f o r m a t i o n between Co a n d Ni from t h e c e m e n t e d carbide a n d Fe, Ni a n d Cr from t h e stainless steel. PREPARATION OF A NICKELCHROMIUM OVERLAY WELD ALLOY CONTAINING FINELY D I S P E R S E D NIOBIUM CARBIDE PARTICLES
T. Tomita et al (Hyogo Inst of I n d u s t r i a l Research, Hyogo, J a p a n ) , J Japan Inst of Metals, Vol 56, No 11, 1992, 1296-1302. (In J a p a n e s e ) . The p r o d u c t i o n of a Ni-20 wt% Cr p o w d e r , 10 p m in size, c o n t a i n i n g a dispersion of a 1.3 p m NbC, using mixing a n d g r a n u l a t i o n of t h e p o w d e r s , is described. The powders are applied to a s u b s t r a t e by a p l a s m a arc process w h i c h m e l t s b o t h c o n s t i t u e n t s of t h e m i x e d powders. The objective of t h e work was to produce a hard, wear and corrosion r e s i s t a n t surface. MECHANICAL T E S T DISCRIMINABILITY FOR T U N G S T E N CARBIDE HARD METALS
B. Roebuck a n d W. Coles (National Physical Laboratory, Teddington, UK), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 127-136. The a b i l i t y of m e c h a n i c a l t e s t s to d i s c r i m i n a t e between m a t e r i a l s differing by small a m o u n t s is discussed. In order to t e s t t h i s two WC-6% Co alloys w e r e p r e p a r e d f r o m p o w d e r s differing by a small a m o u n t in particle size distribution. One specimen showed a uniform d i s t r i b u t i o n of Co a n d WC a n d o t h e r c o n t a i n e d small Co-rich regions several m i c r o n s in size. The h a r d n e s s , n o t c h e d and unnotched bend strengths, plane s t r a i n a n d i n d e n t a t i o n fracture t o u g h n e s s and abrasive wear resistance were compared. The t e s t s used are described in detail. Only t h e n o t c h e d b e n d a n d abrasive w e a r t e s t s showed differences between t h e two materials. NICKEL IN HARDMETALS
V.A. Tracey (Solihull, UK), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 137-149. A review of t h e literature concerning Ni in h a r d m e t a l s a n d cermets is presented. It is shown t h a t Ni can replace, wholly or partly, Co in WC-Co a n d in TiC b a s e m a t e r i a l s , for c u t t i n g t o o l a n d w e a r r e s i s t a n t applications.