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Fracture toughness (Kic of high temperature sintered steel made from recycled powders
PM
WEAR P E R F O R M A N C E OF C O M P O S I T E ALLOYS MADE FROM LOW ALLOY/ HIGH ALLOY S T E E L POWDER MIXTURES P.D. N u r t h e n et al, (Powdrex Ltd, Tonbridge, UK). The d e v e l o p m e n t of w e a r r e s i s t a n t steels, b a s e d o n m i x t u r e s of high speed steel ( H S S ) / l o w alloy steel (LAS) powders, was described. The composite steels combine t h e wear resistance of t h e HSS with t h e lower cost of t h e LAS. C o m p a c t s of green density 7.2 g/cm s can be conventionally sintered withsmall dimensional change. Effects of composition, HSS:LAS ratio, a n d process v a r i a b l e s o n fatigue, i n c l u d i n g r o l l i n g contact fatigue, a n d wear p r o p e r t i e s were reported. The use of HSS/LAS composites for p a r t p r o d u c t i o n was s h o w n to be cost effective. COMPRESSIBILITY AND G R E E N S T R E N G T H OF IRON POWDERS S. Suh et al, (Illinois Inst of Technology, USA) The effects of process p a r a m e t e r s on compressibility a n d density of H-reduced a n d atomized Fe powders were reported. The use of die evacuation was r e p o r t e d to result in a 2.5% increase in green a n d sintered density.
Titanium APPLICATIONS OF MECHANICALLY ALLOYED ( M A ) TITANIUM-COBALT POWDERS FOR COATING SURGICAL IMPLANTS H. Choo et al, (Illinois Inst of Technology, USA). T h e d e v e l o p m e n t of Ti-Co p o w d e r coatings for Ti-6%A1-4%V core materials for use in surgical prostheses was described. The objective was to produce material with a n elastic m o d u l u s g r a d i e n t w h i c h would more closely m a t c h bone, preventing stress shielding and c o n s e q u e n t bone resorption. A m o r p h o u s Ti-Co powders were p r e p a r e d by MA a n d characterized. Consolidation of the Ti-Co p o w d e r s w a s a t t e m p t e d by CIP a n d sintering, h o t pressing a n d slip casting. Mechanical properties of Ti-Co, Ti-Co, Ti6%A1-4°~V a n d Ti-Co coated Ti-6%A1-4%V were compared.
Design and prototypes I 'llrnln.lllr
D E V E L O P M E N T OF S I N T E R E D B E A R I N G S FOR PLANETARY E N G I N E STARTERS H ~ . Rodrigues et al, (Engineered Sintered C o m p o n e n t s , Troutman, N o r t h Carolina,
72 MPR September 1991
LITERATURE
REVIEW
USA). The design steps for sintered bearings were reviewed. The f a c t o r s c o n s i d e r e d included materials properties, capable of supporting the moving parts, bearing dimensions from t h e p o i n t of view of t h e size of t h e h o u s i n g size, t h e type of assembly in w h i c h t h e bering is to be used a n d t h e technology of production.
E F F E C T S OF S I N T E R I N G T E M P E R A T U R E A N D DENSITY ON ROLLING CONTACTS ( R C F ) OF PM STEEL T.M. Cadle et al, (Zenith Sintered Products, Germantown, Wisconsin, USA). O p e r a t i n g c o n d i t i o n s of m a n y PM c o m p o n e n t s were discussed w i t h regard to RCF a n d failure in this mode. The effects of increased density and/or increased sintering temperature o n RCF w e r e reported. A twin wheel and pin test machine was used to quantify the i m p r o v e m e n t in RCF of t h e PM steel a n d grey ductile cast iron a n d w r o u g h t steel were also tested. The PM materials were r e p o r t e d to c o m p a r e favourably w i t h cast iron a n d w r o u g h t steel.
RESTORATION OF S T R E N G T H OF PROTOTYPE PM PARTS M A C H I N E D BY ELECTRICAL D I S C H A R G E MACHINING (EDM) C.J. L a n d g r a f a n d T.M. Cadle, ( Z e n i t h Sintered Products, Germantown, Wisconsin, USA). A discussion of EDM was presented. The i m p o r t a n c e of evaluation of PM a n d o t h e r parts which had been EDM was emphasized. EDM melts t h e surface of a m e t a l b u t not all the m o l t e n m e t a l is removed a n d t h e surface can be left in a highly stressed state. An investigation of EDM w h i c h c o n f i r m e d t h e p o s s i b l e d e t r i m e n t a l effect of EDM on properties a n d t r e a t m e n t s to restore the properties were described.
D E S I G N OF PM C O M P O N E N T S U N D E R ELASTIC/PLASTIC C O N D I T I O N S D. Lindsay a n d H.I. Sanderow, (Browning Manufacturing Co, USA) The i m p o r t a n c e of s t r e s s / s t r a i n models a n d m a t e r i a l s p r o p e r t i e s to t h e design e n g i n e e r was discussed, a n d f u n c t i o n a l c o m p o n e n t t e s t i n g t o verify a d e s i g n described. A t e s t p r o g r a m was used in a design problem: t h e m i n i m u m OD of a part. In a c o m p o n e n t t e s t t h e yield stress was found to be 137.9 MPa b u t in a tensile t e s t t h e yield stress was 141.3 Mpa. The design yield stress was 172.4 MPa a n d a steel with a yield stress of 206.8 MPa was used to e n s u r e t h e p a r t functioned in a n elastic manner.
FRACTURE T O U G H N E S S (IQc) OF HIGH T E M P E R A T U R E S I N T E R E D STEEL MADE FROM RECYCLED POWDERS P. R a m a k r i s h n a n et al, (Indian Inst of Technology, Kanpur, India). T h e r o l e of i m p a c t a n d f r a c t u r e t o u g h n e s s testing fordesign a n d quality control purposes was discussed with respect to t h e value of Kic tests which were said to be valid for sintered steels. Kic values for steel m a e from recycled powders, sintered a t 12908C, were determined. The higher sintering t e m p e r a t u r e was found to increase t h e fracture t o u g h n e s s by 30 to 40% a n d t h i s w a s a t t r i b u t e d to spheroidization of pores.
Electrical and magnetic materials E F F E C T S OF S I N T E R I N G T E M P E R A T U R E A N D SECONDARY E L E M E N T S ON THE SOFT MAGNETIC P R O P E R T I E S O F PM 6.5% SILICON STEEL H.S. C h u n g et al, (Korea Inst of Machinery a n d Metals). It was suggested t h a t PM could be used for t h e p r o d u c t i o n of p a r t s in 6.5%Si steel a n d a n investigation into PM processing a n d t h e effects of additional e l e m e n t s on t h e m a t e r i a l properties was described. It was found t h a t t h e sintered density a n d residual 0 c o n t e n t significantly affected t h e m a g n e t i c properties. Increase in density resulted in increases in flux density a n d p e r m e a b i l i t y a n d r e d u c t i o n in coercive force. Graphite additions reduced residual 0 a n d increased density on sintering a t 1300°C or higher. 0.5%C reduced 0 c o n t e n t to below 300 p p m a n d increased density to above 99% on v a c u u m sintering. In general t h e magnetic properties of t h e PM material were 85% of t h e m a t e r i a l processed from ingots.
MODELLING OF MAGNETIC P H E N O M E N A IN IRON BORON RARE EARTH M A G N E T S E.Y. Yankov a n d Z.P. Popov, (Illinois Inst ofrechnology, USA). A numerical model of reverse magnetization b y m e a n s of d o m a i n b o u n d a r y t r a n s l a t i o n in a n a n i s o t r p i c s p h e r i c a l p a r t i c l e w a s d e s c r i b e d . The m o d e l w a s e x t e n d e d to a s s e m b l i e s of interacting particles. The simulation yields d a t a concerning the effects of particle size, s a t u r a t i o n magnetization size of reversive d o m a i n s on magnetization characteristics. The simulation results were c o m p a r e d with e x p e r i m e n t a l data.
WEAR P E R F O R M A N C E OF C O M P O S I T E ALLOYS MADE FROM LOW ALLOY/ HIGH ALLOY S T E E L POWDER MIXTURES P.D. N u r t h e n et al, (Powdrex Ltd, Tonbridge, UK). The d e v e l o p m e n t of w e a r r e s i s t a n t steels, b a s e d o n m i x t u r e s of high speed steel ( H S S ) / l o w alloy steel (LAS) powders, was described. The composite steels combine t h e wear resistance of t h e HSS with t h e lower cost of t h e LAS. C o m p a c t s of green density 7.2 g/cm s can be conventionally sintered withsmall dimensional change. Effects of composition, HSS:LAS ratio, a n d process v a r i a b l e s o n fatigue, i n c l u d i n g r o l l i n g contact fatigue, a n d wear p r o p e r t i e s were reported. The use of HSS/LAS composites for p a r t p r o d u c t i o n was s h o w n to be cost effective. COMPRESSIBILITY AND G R E E N S T R E N G T H OF IRON POWDERS S. Suh et al, (Illinois Inst of Technology, USA) The effects of process p a r a m e t e r s on compressibility a n d density of H-reduced a n d atomized Fe powders were reported. The use of die evacuation was r e p o r t e d to result in a 2.5% increase in green a n d sintered density.
Titanium APPLICATIONS OF MECHANICALLY ALLOYED ( M A ) TITANIUM-COBALT POWDERS FOR COATING SURGICAL IMPLANTS H. Choo et al, (Illinois Inst of Technology, USA). T h e d e v e l o p m e n t of Ti-Co p o w d e r coatings for Ti-6%A1-4%V core materials for use in surgical prostheses was described. The objective was to produce material with a n elastic m o d u l u s g r a d i e n t w h i c h would more closely m a t c h bone, preventing stress shielding and c o n s e q u e n t bone resorption. A m o r p h o u s Ti-Co powders were p r e p a r e d by MA a n d characterized. Consolidation of the Ti-Co p o w d e r s w a s a t t e m p t e d by CIP a n d sintering, h o t pressing a n d slip casting. Mechanical properties of Ti-Co, Ti-Co, Ti6%A1-4°~V a n d Ti-Co coated Ti-6%A1-4%V were compared.
Design and prototypes I 'llrnln.lllr
D E V E L O P M E N T OF S I N T E R E D B E A R I N G S FOR PLANETARY E N G I N E STARTERS H ~ . Rodrigues et al, (Engineered Sintered C o m p o n e n t s , Troutman, N o r t h Carolina,
72 MPR September 1991
LITERATURE
REVIEW
USA). The design steps for sintered bearings were reviewed. The f a c t o r s c o n s i d e r e d included materials properties, capable of supporting the moving parts, bearing dimensions from t h e p o i n t of view of t h e size of t h e h o u s i n g size, t h e type of assembly in w h i c h t h e bering is to be used a n d t h e technology of production.
E F F E C T S OF S I N T E R I N G T E M P E R A T U R E A N D DENSITY ON ROLLING CONTACTS ( R C F ) OF PM STEEL T.M. Cadle et al, (Zenith Sintered Products, Germantown, Wisconsin, USA). O p e r a t i n g c o n d i t i o n s of m a n y PM c o m p o n e n t s were discussed w i t h regard to RCF a n d failure in this mode. The effects of increased density and/or increased sintering temperature o n RCF w e r e reported. A twin wheel and pin test machine was used to quantify the i m p r o v e m e n t in RCF of t h e PM steel a n d grey ductile cast iron a n d w r o u g h t steel were also tested. The PM materials were r e p o r t e d to c o m p a r e favourably w i t h cast iron a n d w r o u g h t steel.
RESTORATION OF S T R E N G T H OF PROTOTYPE PM PARTS M A C H I N E D BY ELECTRICAL D I S C H A R G E MACHINING (EDM) C.J. L a n d g r a f a n d T.M. Cadle, ( Z e n i t h Sintered Products, Germantown, Wisconsin, USA). A discussion of EDM was presented. The i m p o r t a n c e of evaluation of PM a n d o t h e r parts which had been EDM was emphasized. EDM melts t h e surface of a m e t a l b u t not all the m o l t e n m e t a l is removed a n d t h e surface can be left in a highly stressed state. An investigation of EDM w h i c h c o n f i r m e d t h e p o s s i b l e d e t r i m e n t a l effect of EDM on properties a n d t r e a t m e n t s to restore the properties were described.
D E S I G N OF PM C O M P O N E N T S U N D E R ELASTIC/PLASTIC C O N D I T I O N S D. Lindsay a n d H.I. Sanderow, (Browning Manufacturing Co, USA) The i m p o r t a n c e of s t r e s s / s t r a i n models a n d m a t e r i a l s p r o p e r t i e s to t h e design e n g i n e e r was discussed, a n d f u n c t i o n a l c o m p o n e n t t e s t i n g t o verify a d e s i g n described. A t e s t p r o g r a m was used in a design problem: t h e m i n i m u m OD of a part. In a c o m p o n e n t t e s t t h e yield stress was found to be 137.9 MPa b u t in a tensile t e s t t h e yield stress was 141.3 Mpa. The design yield stress was 172.4 MPa a n d a steel with a yield stress of 206.8 MPa was used to e n s u r e t h e p a r t functioned in a n elastic manner.
FRACTURE T O U G H N E S S (IQc) OF HIGH T E M P E R A T U R E S I N T E R E D STEEL MADE FROM RECYCLED POWDERS P. R a m a k r i s h n a n et al, (Indian Inst of Technology, Kanpur, India). T h e r o l e of i m p a c t a n d f r a c t u r e t o u g h n e s s testing fordesign a n d quality control purposes was discussed with respect to t h e value of Kic tests which were said to be valid for sintered steels. Kic values for steel m a e from recycled powders, sintered a t 12908C, were determined. The higher sintering t e m p e r a t u r e was found to increase t h e fracture t o u g h n e s s by 30 to 40% a n d t h i s w a s a t t r i b u t e d to spheroidization of pores.
Electrical and magnetic materials E F F E C T S OF S I N T E R I N G T E M P E R A T U R E A N D SECONDARY E L E M E N T S ON THE SOFT MAGNETIC P R O P E R T I E S O F PM 6.5% SILICON STEEL H.S. C h u n g et al, (Korea Inst of Machinery a n d Metals). It was suggested t h a t PM could be used for t h e p r o d u c t i o n of p a r t s in 6.5%Si steel a n d a n investigation into PM processing a n d t h e effects of additional e l e m e n t s on t h e m a t e r i a l properties was described. It was found t h a t t h e sintered density a n d residual 0 c o n t e n t significantly affected t h e m a g n e t i c properties. Increase in density resulted in increases in flux density a n d p e r m e a b i l i t y a n d r e d u c t i o n in coercive force. Graphite additions reduced residual 0 a n d increased density on sintering a t 1300°C or higher. 0.5%C reduced 0 c o n t e n t to below 300 p p m a n d increased density to above 99% on v a c u u m sintering. In general t h e magnetic properties of t h e PM material were 85% of t h e m a t e r i a l processed from ingots.
MODELLING OF MAGNETIC P H E N O M E N A IN IRON BORON RARE EARTH M A G N E T S E.Y. Yankov a n d Z.P. Popov, (Illinois Inst ofrechnology, USA). A numerical model of reverse magnetization b y m e a n s of d o m a i n b o u n d a r y t r a n s l a t i o n in a n a n i s o t r p i c s p h e r i c a l p a r t i c l e w a s d e s c r i b e d . The m o d e l w a s e x t e n d e d to a s s e m b l i e s of interacting particles. The simulation yields d a t a concerning the effects of particle size, s a t u r a t i o n magnetization size of reversive d o m a i n s on magnetization characteristics. The simulation results were c o m p a r e d with e x p e r i m e n t a l data.