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Mechanical properties of PM alloy steels
PM
i n c o r p o r a t e d i n t o t h e FEM c o m p u t e r software a n d used to c o m p a r e t h e direct a n d inverse e x t r u s i o n of A1 powders. The ability of t h e FEM software to deal with t h e shape porosity and morphology of deformed particles and thermal and residual stresses for HIP, p o w d e r forging a n d e x t r u s i o n was d e m o n s t r a t e d .
Liquid phase sintering I
I IIIII
THEORY OF ACTIVATED LIQUID P H A S E S I N T E R I N G AND APPLICATION TO C O P P E R - T U N G S T E N ALLOYS J . L J o h n s o n , R.M. German, (Pennsylvania State University, Pennsylvania, USA). Liquid phase sintering (LPS) of i n s o l u b l e s y s t e m s s u c h as Cu-W w a s discussed with regard to t h e h i n d e r a n c e of sintering by t h e insolubility a n d t h e of s i n t e r i n g e n h a n c e r s w h i c h a c t by a s o l u t i o n / p r e c i p i t a t i o n m e c h a n i s m in t h e liquid phase. The use of s i n t e r i n g aids which act by promoting solid state sintering between W grains at contact points was considered and a grain b o u n d a r y diffusion m o d e l was u s e d to calculate activation energies which were r e p o r t e d to be in good a g r e e m e n t w i t h e x p e r i m e n t a l results. EFFECTS OF ATMOSPHERE TEMPERATURE AND COMPOSITION ON D E N S I F I C A T I O N O F NICKEI~ T U N G S T E N - M A N G A N E S E ALLOYS A~ B e l h a d j i h a m i d a , R.M. G e r m a n ( P e n n s y l v a n i a S t a t e University, P e n n s y l v a n i a , USA). The use of W-Ni-Mn alloys as heavy alloy material was discussed and it was suggested t h a t sintering could be carried o u t 300°C below t h a t used for W-Ni-Fe. Sintering of W-Ni-Mn in H was r e p o r t e d to be u n s a t i s f a c t o r y since H does n o t p r e v e n t o x i d a t i o n of Mn, which, coupled with void formation, results in a brittle alloy. Results of a s t u d y of t h e effects of t e m p e r a t u r e , alloy c o m p o s i t i o n a n d sintering a t m o s p h e r e on W-Ni-Mn were presented. These process p a r a m e t e r s were related to m i c r o s t r u c t u r a l evolution and improved sintering and densification were reported. ACTIVATED S I N T E R I N G T H R O U G H T H E P R E S E N C E OF LIQUID P H A S E S M. Courbiere et al (Pechiney -- Centre de Recherches, France). A s t u d y of t h e liquid p h a s e s i n t e r i n g of steel was described for systems in which t r a n s i e n t Fe-Fe2Si a n d Fe-Fe2B eutectics are formed a n d which result in improved densification. M a x i m u m values for %C a n d optimum %B w e r e d e t e r m i n e d . The beneficial effects of B on densification of some commercial Fe alloys was demonstrated.
54 MPR October 1992
LITERATURE
REVIEW
S I N T E R I N G BEHAVIOUR O F COATED POWDERS
A~SINTERED MATERIALS
E. Friedrich et al (Dresden University of Technology, Dresden, Germany). The influence of coatings on powders on s i n t e r i n g b e h a v i o u r was discussed w i t h reference to i m p o r t a n t p a r a m e t e r s , t h e m e t a l , t h i c k n e s s a n d s t r u c t u r e of t h e coating and the substrate. Shrinkage c u r v e s for c o a t e d a n d u n - c o a t e d Fe powders were presented. F o r m a t i o n of a solid solution between coating and s u b s t r a t e w a s r e p o r t e d to c h a n g e t h e s h r i n k a g e b e h a v i o u r d e p e n d i n g on t h e coating t h i c k n e s s a n d aids densification even t h o u g h t h e a m o u n t of liquid p h a s e p r e s e n t is small.
C.M. Lindberg et al ( H o g a n a s AB, Hoganas, Sweden). The p r o p e r t i e s of high s t r e n g t h sintered steels were discussed with reference to t h e need for costly secondary t r e a t m e n t s to overcome t h e p r e s e n c e of weak p h a s e s arising from t h e use of plain Fe powders a n d t h e s t r e n g t h e n i n g of t h e s e phases. Plain Fe powder was replaced by prealloyed Fe-Mo powder. The use of this powder in a single p r e s s / s i n t e r route was r e p o r t e d to r e s u l t in low d i m e n s i o n a l change and tensile strengths up to 900 MPa.
A NEW M O L Y B D E N U M - P H O S P H O R U S S I N T E R E D S T E E L WITH HIGH IMPACT STRENGTH C. Lindberg (Hoeganas AB, Hoeganas, Sweden). The use of u p to 0.6%P to increase t h e i m p a c t s t r e n g t h of PM steel was described. The P as a d d e d as a fine grained ferrop h o s p h o r u s p o w d e r to t h e Fe-Mo powder. The consolidated steel was r e p o r t e d to have i m p a c t s t r e n g t h s up to 100 J after sintering a t 1120°C.
Low alloy steels HIGH PERFORMANCE HEAT TREATED PM S T E E L S W.B. J a m e s , R~I. C a u s t o n (Hoeganas Corporation, Riverton, USA). The c o m b i n a t i o n of properties, s t r e n g t h and ductility, surface hardness and h a r d e n a b i l i t y d e m a n d e d of steel p a r t s was discussed w i t h respect to t h e limited ability of PM m a t e r i a l s to achieve t h e conflicting requirements. The development and p r o p e r t i e s of s t e e l s m a d e f r o m h i g h c o m p r e s s i b i l i t y low alloy steel p o w d e r s w a s c o n s i d e r e d in t h e l i g h t of t h e i r r e s p o n s e to surface h a r d e n i n g t r e a t m e n t s . LOW CARBON PM ALLOY S T E E L S RJ. C a u s t o n et al. (Hoeganas Corporation, Riverton, USA). Process limitations, t e m p e r a t u r e a n d dew point, in t h e s i n t e r i n g of b l e n d e d elemental powders were outlined. A method, w h e r e Mn a n d Cr can be alloyed with high compressibility Fe-Mo p o w d e r to m a k e a high s t r e n g t h low carbon alloy steel was described. High hardenability, conferred by t h e alloy e l e m e n t s results in a bainitic s t r u c t u r e on cooling from t h e sintering t e m p e r a t u r e . Attractive values of tensile p r o p e r t i e s a n d t r a n s v e r s e r u p t u r e s t r e n g t h were reported.
HIGH STRENGTH
MECHANICAL P R O P E R T I E S OF PM ALLOY S T E E L S C.M. Sonsino et al ( F r a u n h o f e r Institut, D a r m s t a d t , Germany). The n e e d s of t h e a u t o m o b i l e industry for high duty PM m a t e r i a l s was discussed. A s t u d y w a s d e s c r i b e d of t h e f a t i g u e p r o p e r t i e s of two s t e e l s . One w a s a d i f f u s i o n alloyed Fe-8%Ni-l%Mo-0.5%C, density 7.5 g/cm 3 and the other Fe-1, 5%Mo-0.5%C d e n s i t y 7.05 g / c m a. As-sintered a n d h e a t treated, n o t c h e d a n d p l a n e s p e c i m e n s were fatigue tested a n d t h e results were r e p o r t e d to show high values of fatigue strength. The suitability of t h e steels for high s t r e s s e d a u t o m o b i l e parts, e.g. gears, was discussed. DOUBLE P R E S S A N D S I N T E R FOR LOW ALLOY S T E E L S FOR H I G H P E R F O R M A N C E APPLICATIONS F~I. Gosselin et al (Quebec Metal Powders, Montreal, C a n a d a ) . The p a p e r r e p o r t e d a study of a double p r e s s / d o u b l e s i n t e r route for a 0.85%Mo low •".lloy steel with various g r a p h i t e additions. Effects of process conditions were studied. The m e c h a n i c a l properties were correlated w i t h t h e microstructure. BIMETAL S I N T E R E D ROCKER ARM F. Blaimschein et al (Miba Sintermetall AG, Vorchdorf, Austria). The p r o p e r t y r e q u i r e m e n t s for a rocker a r m for a three-valve diesel a u t o m o b i l e e n g i n e w e r e d i s c u s s e d in d e t a i l w i t h reference to t h e ability of PM to p r o d u c e a bimetallic component with properties s u p e r i o r to cast or w r o u g h t materials. The design a n d d e v e l o p m e n t of a rocker a r m in which a PM Mo alloyed steel is b o n d e d to a low alloy PM steel during compaction were described. The key factor was the triboiogical properties of t h e Mo steel. The p a r t was m a d e by double compaction a n d sintering was in a c o n t i n u o u s furnace.
i n c o r p o r a t e d i n t o t h e FEM c o m p u t e r software a n d used to c o m p a r e t h e direct a n d inverse e x t r u s i o n of A1 powders. The ability of t h e FEM software to deal with t h e shape porosity and morphology of deformed particles and thermal and residual stresses for HIP, p o w d e r forging a n d e x t r u s i o n was d e m o n s t r a t e d .
Liquid phase sintering I
I IIIII
THEORY OF ACTIVATED LIQUID P H A S E S I N T E R I N G AND APPLICATION TO C O P P E R - T U N G S T E N ALLOYS J . L J o h n s o n , R.M. German, (Pennsylvania State University, Pennsylvania, USA). Liquid phase sintering (LPS) of i n s o l u b l e s y s t e m s s u c h as Cu-W w a s discussed with regard to t h e h i n d e r a n c e of sintering by t h e insolubility a n d t h e of s i n t e r i n g e n h a n c e r s w h i c h a c t by a s o l u t i o n / p r e c i p i t a t i o n m e c h a n i s m in t h e liquid phase. The use of s i n t e r i n g aids which act by promoting solid state sintering between W grains at contact points was considered and a grain b o u n d a r y diffusion m o d e l was u s e d to calculate activation energies which were r e p o r t e d to be in good a g r e e m e n t w i t h e x p e r i m e n t a l results. EFFECTS OF ATMOSPHERE TEMPERATURE AND COMPOSITION ON D E N S I F I C A T I O N O F NICKEI~ T U N G S T E N - M A N G A N E S E ALLOYS A~ B e l h a d j i h a m i d a , R.M. G e r m a n ( P e n n s y l v a n i a S t a t e University, P e n n s y l v a n i a , USA). The use of W-Ni-Mn alloys as heavy alloy material was discussed and it was suggested t h a t sintering could be carried o u t 300°C below t h a t used for W-Ni-Fe. Sintering of W-Ni-Mn in H was r e p o r t e d to be u n s a t i s f a c t o r y since H does n o t p r e v e n t o x i d a t i o n of Mn, which, coupled with void formation, results in a brittle alloy. Results of a s t u d y of t h e effects of t e m p e r a t u r e , alloy c o m p o s i t i o n a n d sintering a t m o s p h e r e on W-Ni-Mn were presented. These process p a r a m e t e r s were related to m i c r o s t r u c t u r a l evolution and improved sintering and densification were reported. ACTIVATED S I N T E R I N G T H R O U G H T H E P R E S E N C E OF LIQUID P H A S E S M. Courbiere et al (Pechiney -- Centre de Recherches, France). A s t u d y of t h e liquid p h a s e s i n t e r i n g of steel was described for systems in which t r a n s i e n t Fe-Fe2Si a n d Fe-Fe2B eutectics are formed a n d which result in improved densification. M a x i m u m values for %C a n d optimum %B w e r e d e t e r m i n e d . The beneficial effects of B on densification of some commercial Fe alloys was demonstrated.
54 MPR October 1992
LITERATURE
REVIEW
S I N T E R I N G BEHAVIOUR O F COATED POWDERS
A~SINTERED MATERIALS
E. Friedrich et al (Dresden University of Technology, Dresden, Germany). The influence of coatings on powders on s i n t e r i n g b e h a v i o u r was discussed w i t h reference to i m p o r t a n t p a r a m e t e r s , t h e m e t a l , t h i c k n e s s a n d s t r u c t u r e of t h e coating and the substrate. Shrinkage c u r v e s for c o a t e d a n d u n - c o a t e d Fe powders were presented. F o r m a t i o n of a solid solution between coating and s u b s t r a t e w a s r e p o r t e d to c h a n g e t h e s h r i n k a g e b e h a v i o u r d e p e n d i n g on t h e coating t h i c k n e s s a n d aids densification even t h o u g h t h e a m o u n t of liquid p h a s e p r e s e n t is small.
C.M. Lindberg et al ( H o g a n a s AB, Hoganas, Sweden). The p r o p e r t i e s of high s t r e n g t h sintered steels were discussed with reference to t h e need for costly secondary t r e a t m e n t s to overcome t h e p r e s e n c e of weak p h a s e s arising from t h e use of plain Fe powders a n d t h e s t r e n g t h e n i n g of t h e s e phases. Plain Fe powder was replaced by prealloyed Fe-Mo powder. The use of this powder in a single p r e s s / s i n t e r route was r e p o r t e d to r e s u l t in low d i m e n s i o n a l change and tensile strengths up to 900 MPa.
A NEW M O L Y B D E N U M - P H O S P H O R U S S I N T E R E D S T E E L WITH HIGH IMPACT STRENGTH C. Lindberg (Hoeganas AB, Hoeganas, Sweden). The use of u p to 0.6%P to increase t h e i m p a c t s t r e n g t h of PM steel was described. The P as a d d e d as a fine grained ferrop h o s p h o r u s p o w d e r to t h e Fe-Mo powder. The consolidated steel was r e p o r t e d to have i m p a c t s t r e n g t h s up to 100 J after sintering a t 1120°C.
Low alloy steels HIGH PERFORMANCE HEAT TREATED PM S T E E L S W.B. J a m e s , R~I. C a u s t o n (Hoeganas Corporation, Riverton, USA). The c o m b i n a t i o n of properties, s t r e n g t h and ductility, surface hardness and h a r d e n a b i l i t y d e m a n d e d of steel p a r t s was discussed w i t h respect to t h e limited ability of PM m a t e r i a l s to achieve t h e conflicting requirements. The development and p r o p e r t i e s of s t e e l s m a d e f r o m h i g h c o m p r e s s i b i l i t y low alloy steel p o w d e r s w a s c o n s i d e r e d in t h e l i g h t of t h e i r r e s p o n s e to surface h a r d e n i n g t r e a t m e n t s . LOW CARBON PM ALLOY S T E E L S RJ. C a u s t o n et al. (Hoeganas Corporation, Riverton, USA). Process limitations, t e m p e r a t u r e a n d dew point, in t h e s i n t e r i n g of b l e n d e d elemental powders were outlined. A method, w h e r e Mn a n d Cr can be alloyed with high compressibility Fe-Mo p o w d e r to m a k e a high s t r e n g t h low carbon alloy steel was described. High hardenability, conferred by t h e alloy e l e m e n t s results in a bainitic s t r u c t u r e on cooling from t h e sintering t e m p e r a t u r e . Attractive values of tensile p r o p e r t i e s a n d t r a n s v e r s e r u p t u r e s t r e n g t h were reported.
HIGH STRENGTH
MECHANICAL P R O P E R T I E S OF PM ALLOY S T E E L S C.M. Sonsino et al ( F r a u n h o f e r Institut, D a r m s t a d t , Germany). The n e e d s of t h e a u t o m o b i l e industry for high duty PM m a t e r i a l s was discussed. A s t u d y w a s d e s c r i b e d of t h e f a t i g u e p r o p e r t i e s of two s t e e l s . One w a s a d i f f u s i o n alloyed Fe-8%Ni-l%Mo-0.5%C, density 7.5 g/cm 3 and the other Fe-1, 5%Mo-0.5%C d e n s i t y 7.05 g / c m a. As-sintered a n d h e a t treated, n o t c h e d a n d p l a n e s p e c i m e n s were fatigue tested a n d t h e results were r e p o r t e d to show high values of fatigue strength. The suitability of t h e steels for high s t r e s s e d a u t o m o b i l e parts, e.g. gears, was discussed. DOUBLE P R E S S A N D S I N T E R FOR LOW ALLOY S T E E L S FOR H I G H P E R F O R M A N C E APPLICATIONS F~I. Gosselin et al (Quebec Metal Powders, Montreal, C a n a d a ) . The p a p e r r e p o r t e d a study of a double p r e s s / d o u b l e s i n t e r route for a 0.85%Mo low •".lloy steel with various g r a p h i t e additions. Effects of process conditions were studied. The m e c h a n i c a l properties were correlated w i t h t h e microstructure. BIMETAL S I N T E R E D ROCKER ARM F. Blaimschein et al (Miba Sintermetall AG, Vorchdorf, Austria). The p r o p e r t y r e q u i r e m e n t s for a rocker a r m for a three-valve diesel a u t o m o b i l e e n g i n e w e r e d i s c u s s e d in d e t a i l w i t h reference to t h e ability of PM to p r o d u c e a bimetallic component with properties s u p e r i o r to cast or w r o u g h t materials. The design a n d d e v e l o p m e n t of a rocker a r m in which a PM Mo alloyed steel is b o n d e d to a low alloy PM steel during compaction were described. The key factor was the triboiogical properties of t h e Mo steel. The p a r t was m a d e by double compaction a n d sintering was in a c o n t i n u o u s furnace.