Effects of sliding friction rate on wear of sintered ferrous alloys as a function of density

Effects of sliding friction rate on wear of sintered ferrous alloys as a function of density

PM E F F E C T S OF SLIDING FRICTION RATE ON WEAR OF S I N T E R E D F E R R O U S ALLOYS AS A FUNCTION OF DENSITY G.F. Bocchini et al (HSgan~is, Rap...

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E F F E C T S OF SLIDING FRICTION RATE ON WEAR OF S I N T E R E D F E R R O U S ALLOYS AS A FUNCTION OF DENSITY G.F. Bocchini et al (HSgan~is, Rapallo, Italy). A study of t h e effects of density friction rate on t h e dry sliding wear of a ferrous alloy, using a n A m s l e r t r i b o m e t e r , was reported. The samples were oil-inbibited. Wear was assessed by weight loss a n d s a m p l e s w e r e e x a m i n e d by s c a n n i n g electron microscopy. It was shown t h a t wear increases with reduction in density a n d increase in sliding friction rate a n d decreases with increase in pressure. It was suggested t h a t oil c o n t a i n e d in t h e pores is squeezed o u t of t h e surface a n d t h e n partially re-absorbed. The oil film t h u s generated prevents microwelding at asperities in the surface.

Magnetic properties E F F E C T S OF POWDER P R O P E R T I E S A N D P R O C E S S I N G ON SOFT MAGNETIC P E R F O R M A N C E OF STAINLESS STEEL H.M. K o p e c h et al ( H o e g a n a e s Corp, Riverton, New Jersey, USA). The m a g n e t i c p r o p e r t i e s of s i n t e r e d 410L and 434L stainless steels were i n v e s t i g a t e d a s f u n c t i o n s of p o w d e r characteristics and process conditions. Magnetic performance was d e t e r m i n e d by practical and theoretical magnetic test methods. SOFT MAGNETIC P R O P E R T I E S OF HIGH DENSITY PM MATERIALS P.T. Hansen et al (Quebec Metal Powders Ltd, Montreal, Quebec, C a n a d a ) . The soft magnetic properties of ferrous alloy were discussed with regard to porosity which was held to have a d e t r i m e n t a l effect on magnetic properties. An investigation of the effects of density, in the range 7.0-7.8 g/ cm 3, on t h e m a g n e t i c p r o p e r t i e s , w a s described. Process conditions were outlined. The effects of process conditions a n d density on magnetic properties were discussed. QUALITY CONTROL OF PM PARTS FOR MAGNETIC APPLICATIONS I~H. Moyer (Magna-Tech PM Labs). Specifications for m a g n e t i c m a t e r i a l s were d i s c u s s e d w i t h r e f e r e n c e to t e s t m e t h o d s a n d it was pointed out t h a t t h e s e apply only to a s - p u r c h a s e d materials. The properties may be altered by s u b s e q u e n t operations such as s h a p i n g or machining. In t h e case of PM p a r t s t h e c o m p o n e n t may be t o o s m a l l to a s s e s s t h e m a g n e t i c properties w h i c h may vary because of t h e s i n t e r i n g p r a c t i c e . P a r t q u a l i t y may, therefore, be variable. A l t h o u g h t h e raw material powders may meet a specification

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t h e finished p a r t may n o t be of t h e required quality.

Particle size effects during sintering E F F E C T S OF T U N G S T E N PARTICLE SIZE A N D POWDER TREATING T E C H N I Q U E S ON T H E S I N T E R E D P R O P E R T I E S OF T U N G S T E N - C O P P E R ALLOYS B. Yang a n d R.M. G e r m a n (Pennsylvania State University, Pennsylvania, USA). Effects of W particle size on shrinkage d u r i n g sintering, d e n s i t y h a r d n e s s a n d m i c r o s t r u c t u r e were investigated. It was shown t h a t good sintered p r o p e r t i e s can be a t t a i n e d by chemically depositing 15 wt% Cu on to s u b m i c r o n W powder a n d sintering in H at 1450°C for 90 mins. Shrinkage is a b o u t 24% a n d the relative density 99.6% giving a Vicker's h a r d n e s s of 382 a n d a s u p e r f i n e m i c r o s t r u c t u r e . Liquid p h a s e s i n t e r i n g r e s u l t s in a m i c r o s t r u c t u r e indicating reprecipitation. A c o m p a r i s o n was m a d e w i t h powder systems t r e a t e d by ball milling a n d coating. PORE I N H I B I T E D GRAIN GROWTH Y. Liu a n d B.R. P a t t e r s o n (University of Alabama, USA). A model for pore i n h i b i t e d grain growth, based on measurable microstructural p a r a m e t e r s , was described. The effects of pore structure, grain size a n d sintering t e m p e r a t u r e were i n v e s t i g a t e d for MgO doped Al203 a n d d a t a from o t h e r m e t a l a n d ceramic systems were presented. The results were r e p o r t e d to d e m o n s t r a t e a n u m b e r of r e l a t i o n s h i p s between grain a n d pore structure. The r e l a t i o n s h i p between grain size a n d pore spacing was found to be linear d e p e n d i n g on d o p a n t c o n c e n t r a t i o n a n d sintering t e m p e r a t u r e . The model was considered to be supported by t h e e x p e r i m e n t a l results. E F F E C T S OF INITIAL POWDER CHARACTERISTICS A N D H O M O G E N E I T Y ON D E N S I F I C A T I O N OF T U N G S T E N - N I C K E L - M A N G A N E S E HEAVY ALLOYS A. B e l h a d j i h a m i d a a n d R.M. G e r m a n (Pennsylvania State University, Pennsylvania, USA). An investigation of t h e effects of initial powder characteristics a n d homogeneity on t h e m e c h a n i c a l p r o p e r t i e s of W-Ni-Mn heavy alloys was described. It was r e p o r t e d t h a t milling of t h e powders a n d use of prealloyed Ni-Mn p o w d e r resulted in reduced pore size a n d increased m e c h a n i c a l properties. The Ni-Mn prealloyed powder was shown to be beneficial in reducing o x i d a t i o n a n d h i g h e r s i n t e r e d densities were obtained. The kinetics of densification associated with initial powder stae were discussed.

Aluminium alloys P R O P E R T I E S OF WROUGHT ALUMINIUM-BERYLLIUM ALLOYS F.C. Greening a n d D. Hashiguchi ( B r u s h Wellman Inc, Elmore, Ohio, USA). Manufacture, properties and applications of A1-Be alloys were reviewed. It was r e p o r t e d t h a t t h e use of i n e r t gas atomized powders a n d consolidation by HIP or e x t r u s i o n r e s u l t e d in p r o d u c t i o n of satisfactory materials with final properties d e p e n d e n t o n process route. Effects of p r o c e s s c o n d i t i o n s of p r o p e r t i e s a n d s t r u c t u r e were discussed. E F F E C T S OF BERYLLIUM C O N T E N T ON PM ALUMINIUM-BERYLLIUM ALLOYS L.M. Beltz a n d R.D. C h e l l m a n (Lockheed Aeronautical Systems Co, USA). Recent d e v e l o p m e n t s in PM A1-Be alloys were o u t l i n e d . It was s h o w n t h a t t h e a d d i t i o n of Be r e s u l t s in i n c r e a s e d m e c h a n i c a l p r o p e r t i e s at a m b i e n t a n d elevated t e m p e r a t u r e s with less anisotropy than found in cast/wrought alloys. Investigations of AI-(40 to 60) %Be alloys. m a d e from spherical AI-Be powders, t~ o p t i m i z e loading c o n d i t i o n s to b a l a n c e s t r e n g t h a n d ductility, were described. A novel process for powder p r o d u c t i o n was r e p o r t e d to reduce t h e cost of t h e materials. Mechanical p r o p e r t i e s of PM a n d ingot m a t e r i a l s were compared. NEW G E N E R A T I O N OF ALUMINIUM ALLOYS FOR SERVICE AT 480°q? S.K. G u h a et al (MER Corp, USA). An investigation of the s t r e n g t h e n i n g effects of tri-aluminides in A1 alloys was described. The m e c h a n i s m p r o p o s e d is the incorporation of ordered dispersed p h a s e s in a disordered m a t r i x with semi-coherent boundaries at dispersoid/matrix boundaries. PM t e c h n i q u e s were used to i n c o r p o r a t e a wide range of dispersoids in t h e alloys. Yield s t r e n g t h s in compression up to 825 MPa were reported.

Cermets and ceramics HIGH THERMAL CONDUCTIVITY SINGLE PHASE A L U M I N I U M N I T R I D E I. Haase a n d G. Himpel (I~A1 e v, Project Ceramics). Difficulties in t h e p r o d u c t i o n of fully dense A1N materials were discussed with reference to use of additives a n d properties. A study of t h e effects of Y203 a n d Y203/CaO additives on t h e t h e r m a l conductivity of sintered A1N was described. Processing was designed to p r o d u c e a single p h a s e m a t e r i a l with a low 0 c o n t e n t a n d a m e c h a n i s m for this was outlined. Results covering effects of pressureless sintering parameters on t h e r m a l conductivity, 0 content, additive levels a n d m i c r o s t r u c t u r e were discussed.

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