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An investigation of compaction in pressing of tungsten heavy alloys
z
~ Jam mIII i~ =1 a~'a~ iI.111]lql = J all ::kval | ~ ' , •
tire reduction is discussed. I[ w a s found t h a t d o p a n t p h a s e particle size i n c r e a s e s with r e d u c t i o n t e m p e r a t u r e .
is s h o w n to s e g r e g a t e at grain b o u n d a r i e s a n d pores in W billets or crack facets in rods a n d wires.
SOLUTION SOFTENING OF IRIDIUM AND RHENIUM IN TUNGSTEN AT ROOM TEMPERATURE
AN INVESTIGATION OF COMPACTION I N P R E S S I N G O F T U N G S T E N HEAVY ALLOYS
A. Lui el al, (Arizona State University, Tempe, Arizona, USA), h~,t J. Refractory
A.L. Lobov et al, (Central Scientific Res e a r c h I n s t i t u t e for F e r r o u s Metallurgy, USSR), Stal', No 10, 1990, 94-97. I n
Metals a n d H a r d Materials, Vol 10, No 2, 1991, 1 0 7 1 1 4 .
Russian.
A t t e n t i o n w a s d r a w n to t h e l o w t e m p e r a t u r e b r i t t l e n e s s of W a n d to a l l e m p t s lo overcome t h i s hy alhrying a n d t h e use of high p u r i t y W. It was s h o w n t h a t the addition of RE to W results in i n c r e a s e s in room t e m p e r a t m e ductility a n d h i g h t e m p e r a t u r e s t r e n g t h . The possible use of Ir was discussed. An investigation of t h e room temperature structure and properties, which h a d theob.jective of e l u c i d a t i n g t h e m e c h a n i s m of sold s o l u t i o n s o f t e n i n g in WIr a n d Ir in t h o r i a t e d W, w a s described.
A s t u d y of c o m p a c t i o n p r o c e s s e s in W-Ni a n d W-Ni-Fe heavy alloys is described. The p o w d e r s used, t h e r e l a t i o n s h i p s b e t w e e n compact density and compressive strength a n d t h e c o m p a c t i n g p r e s s u r e a n d alloy c o m p o s i t i o n are considered.
EFFECTS OF NICKEL:IRON RATIO ON MECHANICAL PROPERTIES OF T U N G S T E N HEAVY ALLOYS
PRODUCTION OF SILVER-TIN OXIDE ELECTRICAL CONTACTS FROM ELECTROLESSLY PLATED COMPOSITE POWDERS
Electrical a n d m a g n e t i c materials
Soc P o w d e r a n d Powder Metallurgy, ~7~1 38, No 4, 1991, 540-547. In Japanese.
H. C h a n g et al, (University of Utah, USA),
"Fire influences of Ni:Fe ratio a n d t h e a d ( l i t i o n o f Co (:,n t h e m e c h a n i c a l properties of W-based heavy alloys have been studied. The Ni:Fe ratio varied in t h e range one p a r t of Ni to one to ten p a ~ s of Fe a n d t h e Co a d d i t i o n s were e i t h e r 0.5 of 1.Owl~?a. M a x i m u m values for s t r e n g t h a n d ductility were l o u n d at Ni:Fe - 1:4 a n d 0.5%Co. The r e s u l t s were d i s c u s s e d in t e r m s of m i c r o s t r u c t u r e , sizes of fracture s o u r c e s and matrix toughness.
Sintered electrical c o n t a c t m a t e r i a l were p r e p a r e d from SnO 2 p o w d e r s w h i c h h a d been p l a t e d with Ag by a novel m e t h o d . The m e c h a n i s m of e l e c t r o l e s s p l a t i n g w a s investigated u s i n g m i x e d p o t e n t i a l theory. The p o w d e r s a n d s i n t e r e d c o n t a c t s w e r e e x a m i n e d by s c a n n i n g electron m i c r o s c o p y and the electrical and mechanical p r o p e r t i e s were m e a s u r e d .
:
strengths obtained.
above
5 0 0 K g l . ' m m ~ we re
MICROSTRUCTURAL CHARACTERISATION OF CEMENTED CARBIDES USING SCANNING ELECTRON MICROSCOPY (SEM) WITH AUTOMATIC IMAGE ANALYIS (AIA) A. Nordgren, (Swedish I n s t i t u t e for Metals R e s e a r c h , S t o c k h o l m , S w e d e n ) , I n t J.
Refractory Metals a n d t l a r d MateriaLs, Vol 10, No 2, 1991, 61-81. The s t r u c t u r e s of WC-Co a n d WC 07-Co (7 - cubic p h a s e s o t h e r t h a n WC) were s t u d i e d by SEM w i t h AIA. The s t u d y was a i m e d at developing t h e use of AIA with c e m e n t e d c a r b i d e s w i t h r e g a r d to t h e d e t e r m i n a t i o n ofcarbide grain size, v o l u m e fraction and contiguity. Optimised specimen preparation, high resolution m i c r o s c o p y a n d i m a g e p r o c e s s i n g were f o u n d to be required. Two m e t h o d s of o b t a i n i n g back s c a t t e r e d electron e o n t r a s t , a t o m i c n u m b e r a n d channelling, were used. The r e s u l t s were r e p o r t e d to be sufficient accuracy for t h e m e t h o d to be u s e d for t h e c h a r a c t e r i s a t i o n of a wide range of h a r d materials.
T. Kaneko, J. Japat~
CONTROL OF PARTICLE SIZE OF TUNGSTEN POWDER
Materials Science a n d E n g i n e e r i n g B, Vol BS, No 2 1991, 99-105.
H a r d m a t e r i a l s a n d tool steels
I). S u e t al, E n g a n d Chcm Metallurgy, Vol
10, No 4, 1989, 67-7"0. I'n Chinese. The eflbcts of p r o c e s s variables on t h e particle size of W powder m a d e by t h e r e d u c t i o n of W blue oxide were investigated in i n d u s t r i a l s c a l e e x p e r i m e n t s . T h e optimum process conditions were e s t a b l i s h e d a n d a n e q u a t i o n for t h e prediction of particle size w a s deduced.
BEHAVIOUR OF TRACE ELEMENT POTASSIUM IN DOPED TUNGSTEN M. Zhou et al, J. Central South l n s t i t u t e o f
M i n i n g a n d Metallurgy (China, Vo120, No 4, 1989, 390-397. In Chinese. The d i s t r i b u t i o n a n d b e h a v i o u r of K in W p o w d e r have been e x a m i n e d as a f u n c t i o n of powder particle size. K c o n t e n t w a s f o u n d to increase with d e c r e a s e in particle size. K
HIGH STRENGTH MICROGRAINED CEMENTED CARBIDES T. F u k a t s u et al, (Toshiba Tungaloy Co Ltd, Kawasaki, J a p a n ) , I n t J. Refractory Metals
a n d H a r d Materials, Vol 10, No 2, 1991, 61-81. An i n v e s t i g a t i o n i n t e n d e d to give i m p r o v e d p r o p e r t i e s to MC-Co m a t e r i a l s is described. C a u s e s of p r o p e r t y reduction, p o r e s , Co p o o l s c o a r s e W g r a i n s a n d i m p u r i t i e s are d i s c u s s e d . The effects of carbide grain growth, inhibitors a n d t h e purity of the raw materials were i n v e s t i g a t e d w i t h respect to d e f e c t s a p p e a r i n g on t h e f r a c t u r e s u r f a c e o f t r a n s v e r s e r u p t u r e d s p e c i m e n s . The r e s u l t s were s h o w n to d e m o n s t r a t e t h a t p o w d e r p u r i t y w a s m o s t significant a n d by u s i n g high p u r i t y WC p o w d e r t r a n s v e r s e r u p t u r e
OPTIMISATION OF PROCESSING PARAMETERS FOR DIRECT VACUUM SINTERING OF A T15 HIGH SPEED STEEL (HSS) M. S a n t o s et al, (LNETI, Lisbon Portugal),
P o w d e r Metallurgy, Vol 34. No 2, 1991, 93100. A s t u d y of t h e v a c u u m s i n t e r i n g of w a t e r a t o m i s e d T15 HSS is described. Effects of p r o c e s s variables, c o m p a c t i n g p r e s s u r e and s i n t e r i n g t e m p e r a t u r e and t h e t i m e were investigated, metallographic and f r a c t o g r a p h i c s t u d i e s w e r e c a r r i e d out. H i g h e s t s t r e n g t h s were a s s o c i a t e d with low p o r o s i t y , t h e a b s e n c e of g r a i n b o u n d a r y films a n d a fine h o m o g e n e o u s m i c r o s t r u c t u r e . It is s u g g e s t e d t h a t cracks e x i s t i n g in fine carbide particles are s u b critical in a f r a c t u r e m e c h a n i c s s e n s e S t u d i e s of g r o u n d a n d g r o u n d p l u s polished specimens showed that grinding a l o n e w a s a d e q u a t e for p r e p a r a t i o n of quality control s p e c i m e n s .
TUNGSTEN CARBIDE HARD METALS CEMENTED WITH FERRO-ALLOYS T. Farooq, T2. Davies, (UMIST/University of Manchester, Manchester, E n g l a n d ) , I n t J.
P o w d e r Metallurgy, Vol 27, No 4, 1991, 34 7-355. WC c e m e n t e d with ferro-alloys ( s t a i n l e s s steel or Fe-Co-NiMoB m a t r i x ) were c h a r a c t e r i s e d for s t r u c t u r e , h a r d n e s s . s t r e n g t h a n d t o u g h n e s s . It w a s f o u n d t h a t high d e n s i t y w a s a t t a i n e d , t h e r e w a s good bonding and high hardness when a s t a i n l e s s steel m a t r i x w a s used. The Fe-
MPR February 1992 59
~ Jam mIII i~ =1 a~'a~ iI.111]lql = J all ::kval | ~ ' , •
tire reduction is discussed. I[ w a s found t h a t d o p a n t p h a s e particle size i n c r e a s e s with r e d u c t i o n t e m p e r a t u r e .
is s h o w n to s e g r e g a t e at grain b o u n d a r i e s a n d pores in W billets or crack facets in rods a n d wires.
SOLUTION SOFTENING OF IRIDIUM AND RHENIUM IN TUNGSTEN AT ROOM TEMPERATURE
AN INVESTIGATION OF COMPACTION I N P R E S S I N G O F T U N G S T E N HEAVY ALLOYS
A. Lui el al, (Arizona State University, Tempe, Arizona, USA), h~,t J. Refractory
A.L. Lobov et al, (Central Scientific Res e a r c h I n s t i t u t e for F e r r o u s Metallurgy, USSR), Stal', No 10, 1990, 94-97. I n
Metals a n d H a r d Materials, Vol 10, No 2, 1991, 1 0 7 1 1 4 .
Russian.
A t t e n t i o n w a s d r a w n to t h e l o w t e m p e r a t u r e b r i t t l e n e s s of W a n d to a l l e m p t s lo overcome t h i s hy alhrying a n d t h e use of high p u r i t y W. It was s h o w n t h a t the addition of RE to W results in i n c r e a s e s in room t e m p e r a t m e ductility a n d h i g h t e m p e r a t u r e s t r e n g t h . The possible use of Ir was discussed. An investigation of t h e room temperature structure and properties, which h a d theob.jective of e l u c i d a t i n g t h e m e c h a n i s m of sold s o l u t i o n s o f t e n i n g in WIr a n d Ir in t h o r i a t e d W, w a s described.
A s t u d y of c o m p a c t i o n p r o c e s s e s in W-Ni a n d W-Ni-Fe heavy alloys is described. The p o w d e r s used, t h e r e l a t i o n s h i p s b e t w e e n compact density and compressive strength a n d t h e c o m p a c t i n g p r e s s u r e a n d alloy c o m p o s i t i o n are considered.
EFFECTS OF NICKEL:IRON RATIO ON MECHANICAL PROPERTIES OF T U N G S T E N HEAVY ALLOYS
PRODUCTION OF SILVER-TIN OXIDE ELECTRICAL CONTACTS FROM ELECTROLESSLY PLATED COMPOSITE POWDERS
Electrical a n d m a g n e t i c materials
Soc P o w d e r a n d Powder Metallurgy, ~7~1 38, No 4, 1991, 540-547. In Japanese.
H. C h a n g et al, (University of Utah, USA),
"Fire influences of Ni:Fe ratio a n d t h e a d ( l i t i o n o f Co (:,n t h e m e c h a n i c a l properties of W-based heavy alloys have been studied. The Ni:Fe ratio varied in t h e range one p a r t of Ni to one to ten p a ~ s of Fe a n d t h e Co a d d i t i o n s were e i t h e r 0.5 of 1.Owl~?a. M a x i m u m values for s t r e n g t h a n d ductility were l o u n d at Ni:Fe - 1:4 a n d 0.5%Co. The r e s u l t s were d i s c u s s e d in t e r m s of m i c r o s t r u c t u r e , sizes of fracture s o u r c e s and matrix toughness.
Sintered electrical c o n t a c t m a t e r i a l were p r e p a r e d from SnO 2 p o w d e r s w h i c h h a d been p l a t e d with Ag by a novel m e t h o d . The m e c h a n i s m of e l e c t r o l e s s p l a t i n g w a s investigated u s i n g m i x e d p o t e n t i a l theory. The p o w d e r s a n d s i n t e r e d c o n t a c t s w e r e e x a m i n e d by s c a n n i n g electron m i c r o s c o p y and the electrical and mechanical p r o p e r t i e s were m e a s u r e d .
:
strengths obtained.
above
5 0 0 K g l . ' m m ~ we re
MICROSTRUCTURAL CHARACTERISATION OF CEMENTED CARBIDES USING SCANNING ELECTRON MICROSCOPY (SEM) WITH AUTOMATIC IMAGE ANALYIS (AIA) A. Nordgren, (Swedish I n s t i t u t e for Metals R e s e a r c h , S t o c k h o l m , S w e d e n ) , I n t J.
Refractory Metals a n d t l a r d MateriaLs, Vol 10, No 2, 1991, 61-81. The s t r u c t u r e s of WC-Co a n d WC 07-Co (7 - cubic p h a s e s o t h e r t h a n WC) were s t u d i e d by SEM w i t h AIA. The s t u d y was a i m e d at developing t h e use of AIA with c e m e n t e d c a r b i d e s w i t h r e g a r d to t h e d e t e r m i n a t i o n ofcarbide grain size, v o l u m e fraction and contiguity. Optimised specimen preparation, high resolution m i c r o s c o p y a n d i m a g e p r o c e s s i n g were f o u n d to be required. Two m e t h o d s of o b t a i n i n g back s c a t t e r e d electron e o n t r a s t , a t o m i c n u m b e r a n d channelling, were used. The r e s u l t s were r e p o r t e d to be sufficient accuracy for t h e m e t h o d to be u s e d for t h e c h a r a c t e r i s a t i o n of a wide range of h a r d materials.
T. Kaneko, J. Japat~
CONTROL OF PARTICLE SIZE OF TUNGSTEN POWDER
Materials Science a n d E n g i n e e r i n g B, Vol BS, No 2 1991, 99-105.
H a r d m a t e r i a l s a n d tool steels
I). S u e t al, E n g a n d Chcm Metallurgy, Vol
10, No 4, 1989, 67-7"0. I'n Chinese. The eflbcts of p r o c e s s variables on t h e particle size of W powder m a d e by t h e r e d u c t i o n of W blue oxide were investigated in i n d u s t r i a l s c a l e e x p e r i m e n t s . T h e optimum process conditions were e s t a b l i s h e d a n d a n e q u a t i o n for t h e prediction of particle size w a s deduced.
BEHAVIOUR OF TRACE ELEMENT POTASSIUM IN DOPED TUNGSTEN M. Zhou et al, J. Central South l n s t i t u t e o f
M i n i n g a n d Metallurgy (China, Vo120, No 4, 1989, 390-397. In Chinese. The d i s t r i b u t i o n a n d b e h a v i o u r of K in W p o w d e r have been e x a m i n e d as a f u n c t i o n of powder particle size. K c o n t e n t w a s f o u n d to increase with d e c r e a s e in particle size. K
HIGH STRENGTH MICROGRAINED CEMENTED CARBIDES T. F u k a t s u et al, (Toshiba Tungaloy Co Ltd, Kawasaki, J a p a n ) , I n t J. Refractory Metals
a n d H a r d Materials, Vol 10, No 2, 1991, 61-81. An i n v e s t i g a t i o n i n t e n d e d to give i m p r o v e d p r o p e r t i e s to MC-Co m a t e r i a l s is described. C a u s e s of p r o p e r t y reduction, p o r e s , Co p o o l s c o a r s e W g r a i n s a n d i m p u r i t i e s are d i s c u s s e d . The effects of carbide grain growth, inhibitors a n d t h e purity of the raw materials were i n v e s t i g a t e d w i t h respect to d e f e c t s a p p e a r i n g on t h e f r a c t u r e s u r f a c e o f t r a n s v e r s e r u p t u r e d s p e c i m e n s . The r e s u l t s were s h o w n to d e m o n s t r a t e t h a t p o w d e r p u r i t y w a s m o s t significant a n d by u s i n g high p u r i t y WC p o w d e r t r a n s v e r s e r u p t u r e
OPTIMISATION OF PROCESSING PARAMETERS FOR DIRECT VACUUM SINTERING OF A T15 HIGH SPEED STEEL (HSS) M. S a n t o s et al, (LNETI, Lisbon Portugal),
P o w d e r Metallurgy, Vol 34. No 2, 1991, 93100. A s t u d y of t h e v a c u u m s i n t e r i n g of w a t e r a t o m i s e d T15 HSS is described. Effects of p r o c e s s variables, c o m p a c t i n g p r e s s u r e and s i n t e r i n g t e m p e r a t u r e and t h e t i m e were investigated, metallographic and f r a c t o g r a p h i c s t u d i e s w e r e c a r r i e d out. H i g h e s t s t r e n g t h s were a s s o c i a t e d with low p o r o s i t y , t h e a b s e n c e of g r a i n b o u n d a r y films a n d a fine h o m o g e n e o u s m i c r o s t r u c t u r e . It is s u g g e s t e d t h a t cracks e x i s t i n g in fine carbide particles are s u b critical in a f r a c t u r e m e c h a n i c s s e n s e S t u d i e s of g r o u n d a n d g r o u n d p l u s polished specimens showed that grinding a l o n e w a s a d e q u a t e for p r e p a r a t i o n of quality control s p e c i m e n s .
TUNGSTEN CARBIDE HARD METALS CEMENTED WITH FERRO-ALLOYS T. Farooq, T2. Davies, (UMIST/University of Manchester, Manchester, E n g l a n d ) , I n t J.
P o w d e r Metallurgy, Vol 27, No 4, 1991, 34 7-355. WC c e m e n t e d with ferro-alloys ( s t a i n l e s s steel or Fe-Co-NiMoB m a t r i x ) were c h a r a c t e r i s e d for s t r u c t u r e , h a r d n e s s . s t r e n g t h a n d t o u g h n e s s . It w a s f o u n d t h a t high d e n s i t y w a s a t t a i n e d , t h e r e w a s good bonding and high hardness when a s t a i n l e s s steel m a t r i x w a s used. The Fe-
MPR February 1992 59