Characteristics and applications of PM stainless steels — An update

Characteristics and applications of PM stainless steels — An update

PM Post sintering treatments STEAM T R E A T M E N T OF S I N T E R I N G F E R R O U S MATERIALS G.F. Bocchini (Hoeganas Italia Srl., Rappa1o, Ital...

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PM

Post sintering treatments STEAM T R E A T M E N T OF S I N T E R I N G F E R R O U S MATERIALS

G.F. Bocchini (Hoeganas Italia Srl., Rappa1o, Italy). S t e a m t r e a t m e n t of PM Fe p a r t s to p r o d u c e a n o x i d e surface c o a t i n g was critically reviewed w i t h r e g a r d to t h e thermodynamics a n d k i n e t i c s of t h e process a n d t h e o p e r a t i n g conditions. It was r e p o r t e d t h a t c o n d i t i o n s in m a n y installations show m a r k e d deviations from t h e ideal. T h e effects of p o r o s i t y on characterization after treatment were evaluated and theoretical assessments were c o m p a r e d with e x p e r i m e n t a l results. Materials selection criteria were p r e s e n t e d and possible ecological factors were considered. NITRACOLOR P R O C E S S TO IMPROVE THE CORROSION R E S I S T A N C E OF S I N T E R E D S T E E L PARTS

H.S. Nayar, T. Philips. (Airco I n d u s t r i a l Gases, Murray Hill, New Jersey, USA). The use of t h e 'Nitracolor' process to produce a corrosion r e s i s t a n t black oxide coating on m e d i u m (0.5%) to high (0.8%) carbon steels with densities 6.6 to 7.0 g/cm 3 was described. The weight gain, h a r d n e s s change, corrosion resistance and decarburization o f t h e s t e e l as functions of %C a n d density were compared. INFLUENCE OF MOLYBDENUM NICKEL AND MANGANESE ON THE AIR H A R D E N I N G OF LOW PREALLOYED POWDER G R A D E S

S. Nigarura et al (Ecole Polytechnique de Montreal, Montreal, C a n a d a ) . The role of Mo in e n h a n c i n g the hardenability of PM low alloy steels c o n t a i n i n g Ni a n d Mn was discussed. The d e v e l o p m e n t of a new grade of Ni-Mo-Mn steel with improved a i r - h a r d e n a b i l i t y a n d mechanical p r o p e r t i e s was outlined. Effects of composition on t h e a m o u n t of m a r t e n s i t e formed on cooling from sintering were described a n d it was shown t h a t t h e need for t h e h e a t t r e a t m e n t can be eliminated.

Stainless steels IMPROVED CORROSION R E S I S T A N T PM STAINLESS S T E E L S

J.H. Reinshagan, R.P. Mason (Ametek Inc., Pennsylvania, USA). The corrosion resistance of PM stainless steels was discussed with respect to pores which act as sites for crevice corrosion a n d t h e d e g r a d i n g of corrosion resistance due to t h e f o r m a t i o n of c a r b i d e s a n d n i t r i d e s during processing. The composition

LITERATURE

REVIEW

s p e c i f i c a t i o n s for s t a i n l e s s s t e e l s were f o r m u l a t e d for w r o u g h t alloys a n d m a y n o t b e o p t i m u m for PM s t e e l s . T h e processing of PM c o n v e n t i o n a l stainless steel for m a x i m u m corrosion r e s i s t a n c e w a s reviewed. T h e p r o p e r t i e s of n e w c o m p o s i t i o n PM s t a i n l e s s s t e e l s w e r e c o m p a r e d w i t h conventional materials.

CORROSION R E S I S T A N C E OF S I N T E R E D S T A I N L E S S S T E E L S WITH NICKEL BASE ADDITIVES

A. S h a r o n et al (Ben Gurion University, Haifa, Israel). A s t u d y of t h e effect of a d d i t i o n s of Nib a s e b r a z i n g p o w d e r on t h e c o r r o s i o n resistance of s i n t e r e d austenitic stainless steel was described. The corrosion resistance was r e p o r t e d to be increased by a d d i t i o n s of t h e brazing p o w d e r in t h e r a n g e 1 to 5wt% a n d t h i s was a t t r i b u t e d to r e d u c t i o n in open i n t e r c o n n e c t e d porosity. At 5% of t h e fine grained additive t h e corrosion resistance of t h e PM steel was c o m p a r a b l e with t h a t of a w r o u g h t alloy a n d coarse grained additive h a d little effect. C h a n g e s in pore morphology, grain size a n d s t r u c t u r e s were reported. PREPARATION AND CHARACTERIZATION OF S T A I N L E S S S T E E L FILTERS

F.A. Filho et al (Inst. de Pequisas Energeticas E Nucleares, Brazil). The p r o d u c t i o n of stainless steel filters from p o w d e r was described. The filters were characterized a n d t h e p r o p e r t i e s correlated with process conditions. It was shown t h a t t h e filter c h a r a c t e r i s t i c s are controlled by s e l e c t i o n of p o w d e r p a r t i c l e sizes a n d s i n t e r e d density. CHARACTERISTICS AND APPLICATIONS OF PM S T A I N L E S S S T E E L S -- AN U P D A T E C.B. Molins et al (Ames S,a~, Barcelona, Spain). The corrosion r e s i s t a n c e of s t a i n l e s s steel was discussed with regard to surface finish a n d porosity. The p a p e r p r e s e n t e d a review of c u r r e n t PM stainless steels, t h e i r mechanical a n d chemical p r o p e r t i e s a n d some industrial applications.

Powder injection moulding IDENTIFICATION OF THE E F F E C T S OF KEY POWDER CHARACTERISTICS ON POWDER I N J E C T I O N MOULDING

R.M. G e r m a n , K.H. H e n s ( P e n n s y l v a n i a State University, USA). A s u m m a r y of t h e c h a r a c t e r i s t i c s of powders for use in injection m o u l d i n g was p r e s e n t e d a n d t h e generic definition of t h e p r o p e r t i e s r e q u i r e d was illustrated. The c h a r a c t e r i s t i c s considered, b i n d e r wetting, rheology, mixing, moulding, d e b i n d i n g a n d sintering were evaluated. The powder properties of concern were shape, i n t e r p a r t i c l e friction, packing density a n d surface polarity. Tests were described a n d typical results were given a n d modifications to improve p e r f o r m a n c e in PIM processing were outlined. A t t e n t i o n was given to links between m o u l d i n g p a r a m e t e r s a n d p o w d e r characteristics. D E V E L O P M E N T OF CARBONYL IRONBASE ALLOY S T E E L POWDERS FOR METAL I N J E C T I O N MOULDING ( M I M )

J.E. J a p k a ( I n t e r n a t i o n a l Speciality Products, USA). D e v e l o p m e n t of Fe-base alloys for MIM, b a s e d on c a r b o n y l Fe were d e s c r i b e d , Sintering and optical and electron microscopy of Fe-Ni, Fe-Co, high -C a n d s t a i n l e s s steels were studied. The alloy c o m p o n e n t s were i n t e n s i v e l y c o m b i n e d t h u s p r o m o t i n g h o m o g e n e i t y in t h e powders. A D O P T I O N OF T H E R M O S E T T I N G C O N D E N S A T I O N RESIN B I N D E R S FOR POWDER I N J E C T I O N MOULDING (VIM)

G.M. Brasel, J.E. Duke (Megamet Industries Inc, St. Louis, USA). The use of t h e r m o s e t t i n g c o n d e n s a t i o n polymers as binders for PIM was discussed. C h a n g e s in t h e b i n d e r d u r i n g m o u l d i n g were described. Porous green p a r t s were r e p o r t e d to have been p r o d u c e d on low p r e s s u r e m o u l d i n g m a c h i n e s a n d for d e b i n d i n g to be rapid.

SINTERED STAINLESS STEELS

MECHANICAL P R O P E R T I E S OF IRONNICKEL METAL INJECTION MOULDED ( M I M ) PARTS

G. Jeszensky, V. Chiaverini (Brazilian Assoc. for Metals, Brazil). The use of PM stainless steel for different a p p l i c a t i o n s was discussed with e m p h a s i s on m e c h a n i c a l a n d corrosion resistance properties. A c o m p a r i s o n of PM stainless steel p a r t s with p a r t s m a d e by o t h e r m e a n s was presented. Production of some p a r t s was described using sintering a t m o s p h e r e s with controlled dew p o i n t s a n d t h e effects of h e a t t r e a t m e n t a n d finishing o p e r a t i o n s was considered.

I~S. Hwang, M.Y. Hsiao. (National Taiwan University The p r o p e r t i e s in MIM Fe-Ni p a r t s m a d e from carbonyl Fe powder, plated with Ni and H reduced, or elemental powder mixtures, were investigated for a d d i t i o n s of Ni up to 8wt%. A m u l t i - c o m p o n e n t b i n d e r was used in the MIM. The highest sintered density was found a t 4 to 6%Ni a n d t h e h i g h e s t tensile s t r e n g t h at 8%. The plated powders gave a more h o m o g e n e o u s p r o d u c t t h a n t h e e l e m e n t a l p o w d e r mixtures.

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