Selection of process route for cemented carbides

Selection of process route for cemented carbides

PM LITERATURE REVIEW 1991 AMPI/MPIF Powder Metallurgy Conference The following a b s t r a c t s are of p a p e r s p r e s e n t e d at t h e conf...

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PM

LITERATURE

REVIEW

1991 AMPI/MPIF Powder Metallurgy Conference The following a b s t r a c t s are of p a p e r s p r e s e n t e d at t h e conference held in Chicago, Illinois, USA, 9-12 J u n e 1991.

Electrical and magnetic materials

were m e a s u r e d a n d it was found t h a t tools w i t h a high BN c o n t e n t a n d a m e t a l m a t r i x s h o w e d t h e lowest w e a r rate, w i t h o u t chipping, a t cutting speeds u p to 300 m / minute.

E F F E C T S OF BORON A D D I T I O N S ON ELECTRICAL A N D MAGNETIC P R O P E R T I E S OF PM IRON-CHROMIUMSILICON-PHOSPHORUS SOFT MAGNETIC MATERIALS

THERMAL D I F F U S I O N ( T D ) APPLICATION OF VANADIUM CARBIDE COATINGS TO PM MATERIALS

E.Y. Yankov et al, (Illinois Inst of Technology, USA) An investigation into t h e effects of B additions on t h e electrical a n d magnetic properties of soft m a g n e t i c materials b a s e d on Fe-Si-Cr-P alloys was described. The properties measured included residual magnetization, Br, coercive force, Hc a n d m a x i m u m p e r m e a b i l i t y , m a x . It w a s suggested t h a t t h e high specific electrical r e s i s t i v i t y a n d s u p e r i o r soft m a g n e t i c properties m a d e t h e alloy suitable for use in AC devices.

H.M. Glaser, (Arvin TD Center, USA). The TD p r o c e s s of coating steel or c e m e n t e d carbide with VC was described. The process involves i m m e r s i o n of t h e p a r t in a salt bath, containing V compounds, a t 980 ° to 1165°C for 8 hours. Steel requires a m i n i m u m C c o n t e n t of 0.3%. VC is formed on a n d in t h e p a r t surface a n d t h e coating is b o n d e d metallurgically to t h e surface a n d is 2 to 20 ]~ thick. The Vickers h a r d n e s s of t h e coating is 3200 to 3800 a n d is said to be wear a n d corrosion r e s i s t a n t a n d to e x t e n d service life by a factor of 50 to 60.

MAGNETIC P R O P E R T I E S A N D CRYSTAL STRUCTURE OF CORROSION RESISTANT IRON NEODYMIUM BORON MAGNETS Y.G. B o g a t i n et al, (SPS Technologies, Jenkintown, Pennsylvania, USA). The effects of p r o c e s s v a r i a b l e s o n crystal structure, magnetic p r o p e r t i e s a n d corrosion resistance of Fe-Nd-B m a g n e t s was investigated in depth. The p h e n o m e n a studied included d e f o r m a t i o n m e c h a n i s m s a n d element distribution. Passivation of t h e particle surfaces was found to produce a n oxide free, corrosion r e s i s t a n t layer.

Hard materials and tool steels MACHINING OF PM MATERIALS WITH CUBIC BORON NITRIDE TOOLS T. Ishikaw a n d K. Okuni, (G.E. Superabrasives, J a p a n ) . The use of a cubic BN cutting tool material for PM m a t e r i a l s was outlined with respect to t h e composition of t h e tool material, metallic a n d ceramic m a t r i x tools being used. Tool wear r a t e s were m e a s u r e d a n d it was found t h a t tools with a high BN c o n t e n t a n d m e t a l wear rates

P R O P E R T I E S A N D S T R U C T U R E S OF M O D I F I E D T U N G S T E N CARBIDECOBALT MATERIALS M.L. Vaidya et al, (Indian Inst of Technology, Kanpur, India). The p a p e r d e s c r i b e d c o r r e l a t i o n of s t r u c t u r e a n d p r o p e r t i e s of WC-10%Co alloys in which t h e carbide a n d m a t r i x p h a s e s h a d been modified by a d d i t i o n s of TiC, Mo2C a n d Ni. TiC a d d i t i o n resulted in a n o n - u n i f o r m s t r u c t u r e with low transverse r u p t u r e strength. Ni a n d Mo2C gave a more uniform s t r u c t u r e a n d b e t t e r properties.

INFLUENCE OF STRUCTURE ON P R O P E R T I E S A N D FRACTURE OF C E M E N T E D CARBIDES M. Rosso et al, (Polytechnic of Turin, Italy). Properties, composition and a p p l i c a t i o n s of c e m e n t e d carbides were discussed. Studies of c e m e n t e d carbides of particle size 1 to 5 ~tm with Co in t h e range 3 to 15wt% were described, s t r u c t u r e a n d properties being investigated. Increases in hardness were found to result from reductions in %Co a n d carbide particle size. 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 w a s increased by increase in %Co.

SELECTION OF P R O C E S S ROUTE FOR CEMENTED CARBIDES M.S. Greenfield et al, ( K e n n a m e t a l Inc, USA). The interaction of processing, compositional and microstructural v a r i a b l e s of c e m e n t e d c a r b i d e s w e r e d i s c u s s e d in r e l a t i o n t o c h a n g e s in mechanical properties. Post densification surface t r e a t m e n t s , grinding a n d coating were discussed with respect to microstructural changes caused by p r e s s u r e s i n t e r i n g or HIP. C o n c l u s i o n s were d r a w n c o n c e r n i n g a p p l i c a b i l i t y of pressure sintering a n d HIP in relation to grade, surface condition a n d uses.

Metal injection moulding J E T T I N G P H E N O M E N O N IN POWDER I N J E C T I O N MOULDING N. Piccirillo, D. Lee, (Rensselaer Polytechnic Inst, Troy, New York, USA). Jetting, t h e n o n - u n i f o r m filling of t h e die in injection m o u l d i n g (IM) a n d its causes, die wall s h e a r rate a n d melt viscosity a n d effects, d e f e c t s in t h e IM p a r t , w e r e reviewed. The c o n d i t i o n s u n d e r w h i c h jetting occurs were stated. The effects of injection rate, gate geometry, a n d die a n d melt t e m p e r a t u r e s were investigated on a n i n s t r u m e n t e d injection moulding m a c h i n e and high speed photography used to visualize m o u l d filling. It was suggested t h a t t h e results o b t a i n e d would assist in quantifying t h e p r o b l e m of jetting.

VACUUM A S S I S T E D I N J E C T I O N MOULDING FOR I M P R O V E M E N T IN QUALITY OF PM PARTS J. Fang, (Beijing Research Inst of Powder Metallurgy, Beijing, China). The factors influencing t h e quality of injection m o u l d e d p a r t s were reviewed, in p a r t i c u l a r t h e role of air e n t r a p p e d in t h e f e e d s t o c k a n d gases evolved f r o m t h e powder/binder mixture during moulding were considered. Vacuum e x t r a c t i o n of t h e m o u l d to remove air a n d gases from t h e m o u l d cavity a n d feedstock as m o u l d i n g proceeds h a s b e e n used in a n effort to improve p a r t quality.

MPR October 1991 57