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Sintering of high surface area tantalum powders
PREPARATION AND APPLICATIONS OF COPPER-CARBON COMPOSITES Z. Zhu et al (Tianjin University, China). The production of Cu-C composites from Cu coated graphite powders was described. The coated C powders were p r e p a r e d by electrodeposition and effects of process conditions on quality were evaluated. The compacts, p r e s s e d and sintered at 85)°C, were r e p o r t e d to have good electrical conductivity, self l u b r i c a t i o n a n d w e a r r e s i s t a n c e . A p p l i c a t i o n s in l o c o m o t i v e overhead slides were discussed.
Lubricants REPLACEMENT OF INTERNAL WITH EXTERNAL LUBRICANTS W.G. Ball et al (Zinc Corp of America, Palmerton, Philadelphia, USA). Use of lubricants in compaction was discussed with respect to p r o b l e m s which may arise. L u b r i c a n t s are m i x e d w i t h powder or may be applied to die walls. A proposal to lubricate die walls, with a precisely m e a s u r e d quantity of lubricant, injected t h r o u g h t h e lower punch, and to omit some or all of the internal lubricant was described. E F F E C T OF LUBRICANT CHEMISTRY ON G R E E N STRENGTH OF COMPACTS S. Masuhara et al (Kobelco Metal Powders, Japan). The influence of lubricants on green properties and processing of c o m p a c t s was discussed. The effects of ethylene b i s t e r a m i d e on g r e e n s t r e n g t h was d e s c r i b e d . The s t u d y c o n c e n t r a t e d on chemical effects and it was r e p o r t e d t h a t the consistency of the powder m i x t u r e was improved as a result of the investigation. CLEANER LUBRICANTS FOR HIGH DENSITY PARTS
t h e n d e f o r m e d in t h e semi-solid s t a t e at different t e m p e r a t u r e s and strain rates. The effects of temperature and strain rate on structures and formability in the semi-solid state were described and discussed. MICROSTRUCTURAL CONTROL BY UNIFORM DROPLET SPRAY TECHNOLOGY T. A n d o et al ( M a s s a c h u s e t t s Inst. of Technology, C a m b r i d g e , M a s s a c h u s e t t s , USA). The ability of spray forming to produce materials with a range of m i c r o s t r n c t u r e s w a s d i s c u s s e d w i t h r e s p e c t to s p r a y p a r a m e t e r s , which, it was p o i n t e d out, need to be controlled i n d e p e n d e n t l y of o n e a n o t h e r . T h i s w a s n o t so w i t h conventional gas atomization. A device to disintegrate a laminar molten metal stream into uniformly sized d r o p l e t s was described. The application to Sn and A1 alloys was reported. The alloys were shown to have uniform and controllable microstructures which were identified. SINTERING OF HIGH SURFACE A R E A TANTALUM POWDERS S.G. Dubois, R.M. German (Pennsylvania State University, Pennsylvania, USA). High surface area Ta powders, for use in electronic capacitors, were discussed and it was noted t h a t t h e r e is a lack of knowledge concerning the sintering of such powders. E x p e r i m e n t s on the sintering at 1000 to 1800°C, with varying t h e r m a l conditions were described. The results were combined with a c o m p u t e r simulation and prediction of sintering m e c h a n i s m s and process parameters. PROCESS DEVELOPMENT FOR S I N T E R E D HIGH S P E E D AND TOOLS S T E E L S -- A S T E P BEYOND ISO 9002
Special materials
P.A. Miller, I~ Bengtsson (Uddeholm, Fairfield, New Jersey, USA). The development of PM technology for the p r o d u c t i o n of fully dense tool steel p a r t s was discussed with reference to a r a n g e of factors. It w a s r e p o r t e d t h a t E l e c t r o s l a g H e a t i n g T e c h n o l o g y (EHT) h a d b e n e i n t r o d u c e d in t h e p o w d e r p r o d u c t i o n stage a n d t h a t as a result inclusion levels in PM steels had been reduced with c o n s e q u e n t i m p r o v e m e n t s in mechanical properties. EHT was discussed and recent d a t a concerning its use were presented.
STRUCTURES AND FORMABILITY OF S I N T E R E D ALUMINIUM-GRAPHITE COMPOSITES
A NEW PROCESS FOR MAKING M2 HIGH S P E E D S T E E L FROM POWDERS WITH A HIGH OXYGEN CONTENT
C-Y.A~ Tsao (Cheng-Kung University, Taiwan). It was r e p o r t e d t h a t PM h a d b e e n used to fabricate A1-C alloys which were
C.C.Ge et al (University of Science and Technology, Beijing, China). The production of M2 HSS from water a t o m i z e d p o w d e r s c o n t a i n i n g 500 t o
W.R. J o n e s et al (Vacuum Furnace Systems Inc, Souderton, Philadelphia, USA). Problems arising from the burning of lubricants during sintering were discussed. It was reported t h a t cleaner lubricants, which reduce c o n t a m i n a t i o n of sintering equipment, had been developed. It was reported t h a t the tensile elongation of a steel p a r t had been increased form 8% to 30% by the use of the new, cleaner, lubricant tensile Strength being 550 MPa.
42 MPR November 1994
6000 p p m O was described. The powders were p r o c e s s e d by magnetic separation, vacuum d e o x i d a t i o n , pressing, sintering and hot extrusion, a shorter process route t h a n previously used. The cleaning effects of t h e process s t e p s and changes in composition were investigated. Densities were m e a s u r e d as functions of p r o c e s s conditions. It was e s t i m a t e d t h a t t h e r e w o u l d be i n c r e a s e d yield of m a t e r i a l and reduced energy c o n s u m p t i o n in the process.
Tungsten heavy alloys E N H A N C E M E N T OF P R O P E R T I E S OF T U N G S T E N HEAVY ALLOYS BY MICROSTRUCTURAL MODIFICATIONS R.M. German et al (Pennsylvania State University, Pennsylvania, USA). It w a s n o t e d that changes in s t r u c t u r e and p r o p e r t i e s of W heavy a l l o y s c a n r e s u l t f r o m c h a n g e s in composition and process conditions. E x p e r i m e n t a l work on W-Ni-Fe, W-Ni-Co a n d W-Ni-Fe-A1 w a s d e s c r i b e d for a wide range of compositions and sintering c o n d i t i o n s in solid a n d liquid s t a t e s . W grain sizes a n d v o l u m e f r a c t i o n of m a t r i x at full density were determined. Effects of p o s t sintering h e a t t r e a t m e n t , to o p t i m i z e p r o p e r t i e s a n d m i n i m i z e impurity levels were discussed. AGING I N D U C E D CHANGES IN MECHANICAL P R O P E R T I E S OF T U N G S T E N HEAVY ALLOYS P. Doepker, L~I. Cuddy (Pennsylvania State University, Pennsylvania, USA). The response of tensile and impact properties of two W-Ni-Co alloys to aging w a s i n v e s t i g a t e d . The alloys were aged at 700 to 1000°C for 3 hours. At 800°C t h e t e n s i l e e l o n g a t i o n d r o p s f r o m 30% t o z e r o a n d t h e C h a r p e y impact also drops, these reductions b e i n g a c c o m p a n i e d b y a c h a n g e in fracture appearance. Higher aging t e m p e r a t u r e s give recovery of ductility and t o u g h n e s s . An e x p l a n a t i o n of t h e s e p h e n o m e n a was proposed. S T R E N G T H E N I N G OF T U N S T E N HEAVY ALLOYS BY A S E C O N D STRAIN AGING TREATMENT Z. Baosheng (General Research Inst. for Non-Ferrous Metals, China). A n i n v e s t i g a t i o n o f t h e e f f e c t s of second strain aging t r e a t m e n t on W-Ni-Fe heavy alloys was described. The alloys w e r e r e d u c e d 22% by c o l d r o l l i n g , vacuum heat t r e a t e d at ll00°C, f u r t h e r cold worked and aged at 300 to 800°C for up to 5 hours. It was r e p o r t e d t h a t the second cold working and aging resulted in a f u r t h e r i n c r e a s e in m e c h a n i c a l p r o p e r t i e s . A p o s s i b l e e x p l a n a t i o n was presented.
Lubricants REPLACEMENT OF INTERNAL WITH EXTERNAL LUBRICANTS W.G. Ball et al (Zinc Corp of America, Palmerton, Philadelphia, USA). Use of lubricants in compaction was discussed with respect to p r o b l e m s which may arise. L u b r i c a n t s are m i x e d w i t h powder or may be applied to die walls. A proposal to lubricate die walls, with a precisely m e a s u r e d quantity of lubricant, injected t h r o u g h t h e lower punch, and to omit some or all of the internal lubricant was described. E F F E C T OF LUBRICANT CHEMISTRY ON G R E E N STRENGTH OF COMPACTS S. Masuhara et al (Kobelco Metal Powders, Japan). The influence of lubricants on green properties and processing of c o m p a c t s was discussed. The effects of ethylene b i s t e r a m i d e on g r e e n s t r e n g t h was d e s c r i b e d . The s t u d y c o n c e n t r a t e d on chemical effects and it was r e p o r t e d t h a t the consistency of the powder m i x t u r e was improved as a result of the investigation. CLEANER LUBRICANTS FOR HIGH DENSITY PARTS
t h e n d e f o r m e d in t h e semi-solid s t a t e at different t e m p e r a t u r e s and strain rates. The effects of temperature and strain rate on structures and formability in the semi-solid state were described and discussed. MICROSTRUCTURAL CONTROL BY UNIFORM DROPLET SPRAY TECHNOLOGY T. A n d o et al ( M a s s a c h u s e t t s Inst. of Technology, C a m b r i d g e , M a s s a c h u s e t t s , USA). The ability of spray forming to produce materials with a range of m i c r o s t r n c t u r e s w a s d i s c u s s e d w i t h r e s p e c t to s p r a y p a r a m e t e r s , which, it was p o i n t e d out, need to be controlled i n d e p e n d e n t l y of o n e a n o t h e r . T h i s w a s n o t so w i t h conventional gas atomization. A device to disintegrate a laminar molten metal stream into uniformly sized d r o p l e t s was described. The application to Sn and A1 alloys was reported. The alloys were shown to have uniform and controllable microstructures which were identified. SINTERING OF HIGH SURFACE A R E A TANTALUM POWDERS S.G. Dubois, R.M. German (Pennsylvania State University, Pennsylvania, USA). High surface area Ta powders, for use in electronic capacitors, were discussed and it was noted t h a t t h e r e is a lack of knowledge concerning the sintering of such powders. E x p e r i m e n t s on the sintering at 1000 to 1800°C, with varying t h e r m a l conditions were described. The results were combined with a c o m p u t e r simulation and prediction of sintering m e c h a n i s m s and process parameters. PROCESS DEVELOPMENT FOR S I N T E R E D HIGH S P E E D AND TOOLS S T E E L S -- A S T E P BEYOND ISO 9002
Special materials
P.A. Miller, I~ Bengtsson (Uddeholm, Fairfield, New Jersey, USA). The development of PM technology for the p r o d u c t i o n of fully dense tool steel p a r t s was discussed with reference to a r a n g e of factors. It w a s r e p o r t e d t h a t E l e c t r o s l a g H e a t i n g T e c h n o l o g y (EHT) h a d b e n e i n t r o d u c e d in t h e p o w d e r p r o d u c t i o n stage a n d t h a t as a result inclusion levels in PM steels had been reduced with c o n s e q u e n t i m p r o v e m e n t s in mechanical properties. EHT was discussed and recent d a t a concerning its use were presented.
STRUCTURES AND FORMABILITY OF S I N T E R E D ALUMINIUM-GRAPHITE COMPOSITES
A NEW PROCESS FOR MAKING M2 HIGH S P E E D S T E E L FROM POWDERS WITH A HIGH OXYGEN CONTENT
C-Y.A~ Tsao (Cheng-Kung University, Taiwan). It was r e p o r t e d t h a t PM h a d b e e n used to fabricate A1-C alloys which were
C.C.Ge et al (University of Science and Technology, Beijing, China). The production of M2 HSS from water a t o m i z e d p o w d e r s c o n t a i n i n g 500 t o
W.R. J o n e s et al (Vacuum Furnace Systems Inc, Souderton, Philadelphia, USA). Problems arising from the burning of lubricants during sintering were discussed. It was reported t h a t cleaner lubricants, which reduce c o n t a m i n a t i o n of sintering equipment, had been developed. It was reported t h a t the tensile elongation of a steel p a r t had been increased form 8% to 30% by the use of the new, cleaner, lubricant tensile Strength being 550 MPa.
42 MPR November 1994
6000 p p m O was described. The powders were p r o c e s s e d by magnetic separation, vacuum d e o x i d a t i o n , pressing, sintering and hot extrusion, a shorter process route t h a n previously used. The cleaning effects of t h e process s t e p s and changes in composition were investigated. Densities were m e a s u r e d as functions of p r o c e s s conditions. It was e s t i m a t e d t h a t t h e r e w o u l d be i n c r e a s e d yield of m a t e r i a l and reduced energy c o n s u m p t i o n in the process.
Tungsten heavy alloys E N H A N C E M E N T OF P R O P E R T I E S OF T U N G S T E N HEAVY ALLOYS BY MICROSTRUCTURAL MODIFICATIONS R.M. German et al (Pennsylvania State University, Pennsylvania, USA). It w a s n o t e d that changes in s t r u c t u r e and p r o p e r t i e s of W heavy a l l o y s c a n r e s u l t f r o m c h a n g e s in composition and process conditions. E x p e r i m e n t a l work on W-Ni-Fe, W-Ni-Co a n d W-Ni-Fe-A1 w a s d e s c r i b e d for a wide range of compositions and sintering c o n d i t i o n s in solid a n d liquid s t a t e s . W grain sizes a n d v o l u m e f r a c t i o n of m a t r i x at full density were determined. Effects of p o s t sintering h e a t t r e a t m e n t , to o p t i m i z e p r o p e r t i e s a n d m i n i m i z e impurity levels were discussed. AGING I N D U C E D CHANGES IN MECHANICAL P R O P E R T I E S OF T U N G S T E N HEAVY ALLOYS P. Doepker, L~I. Cuddy (Pennsylvania State University, Pennsylvania, USA). The response of tensile and impact properties of two W-Ni-Co alloys to aging w a s i n v e s t i g a t e d . The alloys were aged at 700 to 1000°C for 3 hours. At 800°C t h e t e n s i l e e l o n g a t i o n d r o p s f r o m 30% t o z e r o a n d t h e C h a r p e y impact also drops, these reductions b e i n g a c c o m p a n i e d b y a c h a n g e in fracture appearance. Higher aging t e m p e r a t u r e s give recovery of ductility and t o u g h n e s s . An e x p l a n a t i o n of t h e s e p h e n o m e n a was proposed. S T R E N G T H E N I N G OF T U N S T E N HEAVY ALLOYS BY A S E C O N D STRAIN AGING TREATMENT Z. Baosheng (General Research Inst. for Non-Ferrous Metals, China). A n i n v e s t i g a t i o n o f t h e e f f e c t s of second strain aging t r e a t m e n t on W-Ni-Fe heavy alloys was described. The alloys w e r e r e d u c e d 22% by c o l d r o l l i n g , vacuum heat t r e a t e d at ll00°C, f u r t h e r cold worked and aged at 300 to 800°C for up to 5 hours. It was r e p o r t e d t h a t the second cold working and aging resulted in a f u r t h e r i n c r e a s e in m e c h a n i c a l p r o p e r t i e s . A p o s s i b l e e x p l a n a t i o n was presented.