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Sintering mechanisms of TiCCr3C2 ceramic composites
Nickel
Tungsten
COMPACTIBILITY OF HIGHLY D I S P E R S E D Ni POWDERS AND ROLLING OF THIN POROUS STRIPS
E F F E C T OF PHOSPHORUS CONTENT ON THE IMPACT STRENGTH OF T U N G S T E N HEAVY ALLOY
I v a n o v , e t al, P o r o s k o v a y a Metallurgiya, No 6, 1990, 23-26. In Russian.
S-H.Hong, et al, (Inst. of Advanced Science and Technology, Seoul, Korea), Powder Metallurgy International, Vol 22, No 6, 1990, 24-31. The addition of up to 300 p p m of P was shown to reduce the impact strength of W4.9Ni-2.1Fe heavy alloy even after heat t r e a t m e n t at 1150~C and water quenching. The e m b r i t t l e m e n t is o b s e r v e d a t P c o n c e n t r a t i o n s n o r m a l for t h i s alloy. Structure and composition (Auger s p e c t r o s c o p y was used for s u r f a c e analysis) show t h a t the e m b r i t t l e m e n t can be attributed to segregation of P at the grain-matrix interface. The impact strength was found to decrease with decreasing heat t r e a t m e n t t e m p e r a t u r e and cooling rate in a c c o r d a n c e w i t h the m e c h a n i s m of segregation of impurities to interfaces.
A.M.
The compactibility of Ni powders with specific surface in the range 2.5-12 m~/g has been studied. Effect of pressure on density of compacts as a function of specific surface was measured. The ability of the powder to be rolled into strip with 40-70% porosity and 30-70 #m in thickness has been established.
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF E X T R U D E D BARS FORMED FROM Ar-ATOMIZED Ni-BASE SUPERALLOY POWDERS J.S. Park, et al, (Seoul National University, Seoul, Korea), J. Korean Inst. of Metals, Vol 26, No 9, 1990, 825-832. In Korean. The p a p e r d r a w s a t t e n t i o n to a n d explains the beneficial effects of W and Mo on the structure and properties of Nibase superalloys. The effect of Mo additions on e x t r u d e d bar made from Ar-atomized superalloy powders was investigated. The powders were found to have a dendritic structure. The volume fraction of the 7' p h a s e in the e x t r u d e d bar was increased from 55 to 65% when the Mo content was increased from 0.97 to 4.68 wt%. This resulted in an increase in strength of 100 MPa in the range 650 to 850°C. Smaller increases were found above 850°C.
STRUCTURE AND MECHANICAL PROPERTIES OF W-Ni-Cu ALLOYS K a l i n i n a , e t al, P o r o s k o v a y a Metallurgiya, No 5, 1990, 80-83. In Russian. M.M.
The effects of thermochemical t r e a t m e n t on the structure and properties of PM W3Ni-2Cu has been examined. It has been shown t h a t the d e p t h of p e n e t r a t i o n of W into the Ni-Cu matrix is d e t e r m i n e d by the cooling rate from the liquid p h a s e sintering temperature. A m e c h a n i s m for the effects of thermochemical t r e a t m e n t on properties is proposed.
E F F E C T S OF DOPING A G E N T S ON THE HIGH TEMPERATURE S T R E N G T H OF PM T U N G S T E N WIRE
Niobium ..............
-
.
SINTERING CONDITIONS AND STRUCTURE OF POROUS NIOBIUM L e v i n s k y , e t al, P o r o s k o v a y a Metallurgiya, No 5, 1990, 29+33. In Russian.
T.V.
The effect of powder dispersivity on the sintering of Nb c o m p a c t s was studied. An expansion was noted in the initial stage of sintering and this is said to be related to the dispersivity. Shrinkage of the more dispersed powders is initiated at lower t e m p e r a t u r e s and proceeds more rapidly t h a n in c o a r s e r g r a i n e d p o w d e r s . At porosity above 40% the original particles are retained and below 40% continuous skeletons of metal pores are observed in the microstructure.
K. Tanoue, et al, (Kyushu I n s t i t u t e of Technology, Kitaktushu, J a p a n ) , J. Japan Inst. of Metals, Vol 53, No 9, 1990. In Japanese. The effects of d o p a n t s and heating rates on t h e c h a r a c t e r i s t i c s o f s e c o n d a r y recrystallization a n d t h e effect of t h e latter on the high t e m p e r a t u r e strength, particularly creep strength, of PM W wire have been examined. Fractures are t r a n s g r a n u l a r (ductile) for doped wire but intergranular for non-doped material. The stress c o m p o n e n t of the creep power law s h o w s d e p e n d e n c e on s t r e s s , m a i n l y internal stress. This is attributed to the possibility of bubbles in d o p e d wire and the characteristic configuration, long elongated grains, of the secondary recrystallization structure.
Coatings PRODUCTION OF FUNCTIONALLY GRADIENT MATERIALS ( F G M ) BY A GAS P R E S S U R E COMBUSTION SINTERING PROCESS F. Matsuzaki, et al, J. Japat~ Soe. Powder and Powder Metallurg.q, Vol 37, No 7, 1990, 937-941. In Japanese. A process for the production of a MoSie/ SiC c o a t i n g on a TiA1 s u b s t r a t e , for aerospace applications is described. The gas pressure combustion sintering process, coupled with HIP, is used. The coated material is shown to have good oxidation resistance and high t e m p e r a t u r e strength. The structure of the coating was examined by X-ray diffraction and microscopy.
Ceramics SINTERING MECHANISMS OF TiCCr3C 2 CERAMIC COMPOSITES T. tiachisuka, J. Japan Soc. Powder and Powder Metallurgy, Vol 37+ No 6, 199(), 861 868. In Japanese. The sintering behaviour of TiC-Cr:~Cz ceramic composites containing 1% metallic impurities was investigated as a function of TiC content. It was shown that densification improved as a result of using the carbide mixture compared with the single carbides. The metallic impurities studied were found to dissolve in the CruC2 during sintering. Full density could be attained on sintering at less than 1600 C. TRANSFORMATION T O U G H E N E D ALUMINA OBTAINED BY A REACTION SPRAY PROCESS T. Haug, et al, (Dornier GmbH, Friedrich s h a f e n , G e r m a n y ) , Powder Metallurgy International, Vol 22, No 5, 1990, 32-34. A l u m i n a c e r a m i c s , t o u g h e n e d by a h o m o g e n e o u s d i s t r i b u t i o n of zirconia, have been produced by a reaction spray process in which aqueous solutions are sprayed into a hot reaction vessel. For alumina powder with 20% zirconia and f u r t h e r additions, s t r e n g t h s of 700-800 MPa and toughnesses 8+10 MPa/m 1/u were obtained.
Electrical and mechanical materials MICROSTRUCTURE OF SINTERED FeNd-B MAGNETS G. Schneider, et al, (Foundation for Indust r i a l T e c h n o l o g y , L o r e n a , B r a s i l ) , Z. Metallkunde, Vol 81, No 5, 1990, 322-329.
MPR
March
1991
57
Tungsten
COMPACTIBILITY OF HIGHLY D I S P E R S E D Ni POWDERS AND ROLLING OF THIN POROUS STRIPS
E F F E C T OF PHOSPHORUS CONTENT ON THE IMPACT STRENGTH OF T U N G S T E N HEAVY ALLOY
I v a n o v , e t al, P o r o s k o v a y a Metallurgiya, No 6, 1990, 23-26. In Russian.
S-H.Hong, et al, (Inst. of Advanced Science and Technology, Seoul, Korea), Powder Metallurgy International, Vol 22, No 6, 1990, 24-31. The addition of up to 300 p p m of P was shown to reduce the impact strength of W4.9Ni-2.1Fe heavy alloy even after heat t r e a t m e n t at 1150~C and water quenching. The e m b r i t t l e m e n t is o b s e r v e d a t P c o n c e n t r a t i o n s n o r m a l for t h i s alloy. Structure and composition (Auger s p e c t r o s c o p y was used for s u r f a c e analysis) show t h a t the e m b r i t t l e m e n t can be attributed to segregation of P at the grain-matrix interface. The impact strength was found to decrease with decreasing heat t r e a t m e n t t e m p e r a t u r e and cooling rate in a c c o r d a n c e w i t h the m e c h a n i s m of segregation of impurities to interfaces.
A.M.
The compactibility of Ni powders with specific surface in the range 2.5-12 m~/g has been studied. Effect of pressure on density of compacts as a function of specific surface was measured. The ability of the powder to be rolled into strip with 40-70% porosity and 30-70 #m in thickness has been established.
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF E X T R U D E D BARS FORMED FROM Ar-ATOMIZED Ni-BASE SUPERALLOY POWDERS J.S. Park, et al, (Seoul National University, Seoul, Korea), J. Korean Inst. of Metals, Vol 26, No 9, 1990, 825-832. In Korean. The p a p e r d r a w s a t t e n t i o n to a n d explains the beneficial effects of W and Mo on the structure and properties of Nibase superalloys. The effect of Mo additions on e x t r u d e d bar made from Ar-atomized superalloy powders was investigated. The powders were found to have a dendritic structure. The volume fraction of the 7' p h a s e in the e x t r u d e d bar was increased from 55 to 65% when the Mo content was increased from 0.97 to 4.68 wt%. This resulted in an increase in strength of 100 MPa in the range 650 to 850°C. Smaller increases were found above 850°C.
STRUCTURE AND MECHANICAL PROPERTIES OF W-Ni-Cu ALLOYS K a l i n i n a , e t al, P o r o s k o v a y a Metallurgiya, No 5, 1990, 80-83. In Russian. M.M.
The effects of thermochemical t r e a t m e n t on the structure and properties of PM W3Ni-2Cu has been examined. It has been shown t h a t the d e p t h of p e n e t r a t i o n of W into the Ni-Cu matrix is d e t e r m i n e d by the cooling rate from the liquid p h a s e sintering temperature. A m e c h a n i s m for the effects of thermochemical t r e a t m e n t on properties is proposed.
E F F E C T S OF DOPING A G E N T S ON THE HIGH TEMPERATURE S T R E N G T H OF PM T U N G S T E N WIRE
Niobium ..............
-
.
SINTERING CONDITIONS AND STRUCTURE OF POROUS NIOBIUM L e v i n s k y , e t al, P o r o s k o v a y a Metallurgiya, No 5, 1990, 29+33. In Russian.
T.V.
The effect of powder dispersivity on the sintering of Nb c o m p a c t s was studied. An expansion was noted in the initial stage of sintering and this is said to be related to the dispersivity. Shrinkage of the more dispersed powders is initiated at lower t e m p e r a t u r e s and proceeds more rapidly t h a n in c o a r s e r g r a i n e d p o w d e r s . At porosity above 40% the original particles are retained and below 40% continuous skeletons of metal pores are observed in the microstructure.
K. Tanoue, et al, (Kyushu I n s t i t u t e of Technology, Kitaktushu, J a p a n ) , J. Japan Inst. of Metals, Vol 53, No 9, 1990. In Japanese. The effects of d o p a n t s and heating rates on t h e c h a r a c t e r i s t i c s o f s e c o n d a r y recrystallization a n d t h e effect of t h e latter on the high t e m p e r a t u r e strength, particularly creep strength, of PM W wire have been examined. Fractures are t r a n s g r a n u l a r (ductile) for doped wire but intergranular for non-doped material. The stress c o m p o n e n t of the creep power law s h o w s d e p e n d e n c e on s t r e s s , m a i n l y internal stress. This is attributed to the possibility of bubbles in d o p e d wire and the characteristic configuration, long elongated grains, of the secondary recrystallization structure.
Coatings PRODUCTION OF FUNCTIONALLY GRADIENT MATERIALS ( F G M ) BY A GAS P R E S S U R E COMBUSTION SINTERING PROCESS F. Matsuzaki, et al, J. Japat~ Soe. Powder and Powder Metallurg.q, Vol 37, No 7, 1990, 937-941. In Japanese. A process for the production of a MoSie/ SiC c o a t i n g on a TiA1 s u b s t r a t e , for aerospace applications is described. The gas pressure combustion sintering process, coupled with HIP, is used. The coated material is shown to have good oxidation resistance and high t e m p e r a t u r e strength. The structure of the coating was examined by X-ray diffraction and microscopy.
Ceramics SINTERING MECHANISMS OF TiCCr3C 2 CERAMIC COMPOSITES T. tiachisuka, J. Japan Soc. Powder and Powder Metallurgy, Vol 37+ No 6, 199(), 861 868. In Japanese. The sintering behaviour of TiC-Cr:~Cz ceramic composites containing 1% metallic impurities was investigated as a function of TiC content. It was shown that densification improved as a result of using the carbide mixture compared with the single carbides. The metallic impurities studied were found to dissolve in the CruC2 during sintering. Full density could be attained on sintering at less than 1600 C. TRANSFORMATION T O U G H E N E D ALUMINA OBTAINED BY A REACTION SPRAY PROCESS T. Haug, et al, (Dornier GmbH, Friedrich s h a f e n , G e r m a n y ) , Powder Metallurgy International, Vol 22, No 5, 1990, 32-34. A l u m i n a c e r a m i c s , t o u g h e n e d by a h o m o g e n e o u s d i s t r i b u t i o n of zirconia, have been produced by a reaction spray process in which aqueous solutions are sprayed into a hot reaction vessel. For alumina powder with 20% zirconia and f u r t h e r additions, s t r e n g t h s of 700-800 MPa and toughnesses 8+10 MPa/m 1/u were obtained.
Electrical and mechanical materials MICROSTRUCTURE OF SINTERED FeNd-B MAGNETS G. Schneider, et al, (Foundation for Indust r i a l T e c h n o l o g y , L o r e n a , B r a s i l ) , Z. Metallkunde, Vol 81, No 5, 1990, 322-329.
MPR
March
1991
57