Corrosion resistance of full density sintered 316L stainless steel

Corrosion resistance of full density sintered 316L stainless steel

96% IACS ( I n t e r n a t i o n a l A n n e a l e d Copper S t a n d a r d ) . The c o m p a r a b l e figures for Zn s t e a r a t e were 94% a n d ...

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96% IACS ( I n t e r n a t i o n a l A n n e a l e d Copper S t a n d a r d ) . The c o m p a r a b l e figures for Zn s t e a r a t e were 94% a n d 87%. This was a t t r i b u t e d to t h e d e c o m p o s i t i o n of Li s t e a r a t e to Li20 whereas Zn s t e a r a t e is lost by volatilization. The presence of A1 e n h a n c e s sintering giving densities of 99% b u t the conductivity is lower a t 84% IACS.

p a r t i c u l a r t h e elimination of compacting lubricant decomposition. At low t e m p e r a t u r e s in t h e range 545 to 665°C t h e l u b r i c a n t d e c o m p o s e s to g a s e o u s c o m p o u n d s b u t above 730°C c a r b o n is deposited a n d interferes with infiltration. It was suggested t h a t o t h e r processes m i g h t replace infiltration.

USA). The effects of different lubricants used in t h e p r e s s i n g of s t e e l p o w d e r s o n Cu infiltration were reported. A t t e n t i o n was drawn to infiltration efficiency a n d time, erosion a n d surface finish with t h e objective of increasing the understanding of infiltration.

MACHINING CHARACTERISTICS OF LEADED AND NON-LEADED PM BRASS AS I N F L U E N C E D BY S E L E C T ADDITIVES

HOMOGENIZATION PROCESSING OF A PM MARAGING STEEL

WEAR OF STEAMED FERROUS SINTERED MATERIALS OF VARYING DENSITIES

T.W. Pelletiers a n d P.E. Matthews, (U.S. Bronze Inc, Flemington, New Jersey, USA). An investigation into t h e effects of Pb a n d o t h e r a d d i t i v e s in p r o m o t i n g t h e machinability o f PM b r a s s e s was described. The objective was, for various reasons connected with restrictions on t h e use of Pb, to reduce or eliminate Pb in Cu alloys. Specimens were evaluated by drilling tests u n d e r s t a n d a r d i z e d conditions a n d o t h e r mechanical tests.

D.W. Smith a n d W.A. J o h n s o n , (Michigan Technological Univ, USA). Research aimed at t h e p r o d u c t i o n of low p o r o s i t y PM m a r a g i n g steel c o n t a i n i n g 18%Ni, 9%Co a n d 5%Mo was described. The steel powders were made by h o m o g e n i z a t i o n processing of e l e m e n t a l p o w d e r m i x t u r e s . S i n t e r e d d e n s i t i e s of 95% could be a t t a i n e d by pressing a n d sintering, a n d full density by sinter/HIP processing. P r o c e s s i n g c o n d i t i o n s were discussed. Tensile s t r e n g t h s above 1375 MPa a n d reduction of area of 50% were attained.

Iron a n d s t e e l 'n

NEW 2%Ni-l%Mo STEEL FOR HIGH STRENGTH COMPONENTS

S. Takajo et al, (Kawasaki Steel Corp, Kawasaki, J a p a n ) . The d e v e l o p m e n t of 2%Ni-l%Mo high s t r e n g t h PM steel was reported. The steel is produced from prealloyed p o w d e r which is pressed, sintered a n d h e a t treated. Tensile s t r e n g t h s u p to 1960 MPa w i t h good ductility a n d t h i s is a t t r i b u t e d to t h e s t r a i n induced m a r t e n s i t i c t r a n s f o r m a t i o n of Ni rich r e t a i n e d a u s t e n i t e during tensile testing. Prior to heat treatment the compacts are sufficiently soft to p e r m i t m a c h i n i n g or sizing. D E S I G N CRITERIA IN THE MANUFACTURE OF LOW ALLOY STEEL POWDERS

Y. Trudel et al, (Quebec Metal Powders Ltd, Montreal, Quebec, C a n a d a ) . A p r o g r a m m e of testing the effects of Mn, Cr, Ni a n d Mo, singly or in a n y combination, on t h e properties of w a t e r atomized prealloyed powders was described. Design criteria were established for p r o d u c t properties including residual C a n d O, p o w d e r compressibility, s t r e n g t h and hardenability. Jominy tests were carried out on a wide range of compositions, a n d thecapability to m e e t design criteria was discussed. INFILTRATION -- 'TO B E OR NOT TO BE'

W.G. Ball, (Zinc Corp of America, Palmerton, Pennsylvania, USA). Cu infiltration into steel was reviewed with regard to factors influencing it. In

70 MPR September 1991

CORROSION RESISTANCE OF FULL DENSITY S I N T E R E D 316L STAINLESS STEEL

I~M. Kulkarni a n d R.F. Palmateer, (Advanced Metalworking Practices Inc, Carmetl, Indiana, USA). Corrosion resistance of 316L stainless steel with densities of 85 to 90% were reviewed. The p a p e r w e n t on to describe t h e corrosion resistance of t h e same steel a t a h i g h e r d e n s i t y (96%) w h i c h h a d b e e n t r e a t e d to p r e v e n t t h e p r e c i p i t a t i o n of grain boundary carbides and nitrides. Testing h a d been carried o u t u n d e r a wide range of conditions a n d it was r e p o r t e d t h a t t h e corrosion resistance of t h e high density steel a p p r o a c h e d t h a t of w r o u g h t stainless steel and was superior to that of conventional PM stainless steel a n d cast products. MECHANICAL PROPERTIES OF INFILTRATED HEAT TREATED CARBON S T E E L S

V.S. Styskin a n d D.D. Clapp, (The Wakefield Corp, Wakefield, Maryland, USA) The p a p e r r e p o r t e d research on t h e mechanical properties of infiltrated steels with regard to process variables. O p t i m u m Cu a n d C c o n t e n t s were established. Effect of m a t r i x d e n s i t y o n p r o p e r t i e s w a s considered. Comparison was made b e t w e e n o n e a n d two s t e p s i n t e r i n g processes on properties a n d d i m e n s i o n a l changes during sintering. E F F E C T S OF COMPACTING LUBRICANTS ON S U B S E Q U E N T COPPER INFILTRATION

R.M. G o t h a m a n d A. D e c h e r t , ( A l c a n Powders a n d Pigments, Union, New Jersey,

G.B. Bigiero et al, (Univ of Rome, Italy). Wear t e s t s on steels of densities 6.5, 6.8, 7.1 a n d 7.3 g/cm 3 were reported. Effects of s t e a m i n g to produce a n oxide film were i n v e s t i g a t e d . It w a s f o u n d t h a t s t e a m t r e a t m e n t increases wear resistance u n d e r lubricated conditions. 'NITRABLACK' P R O C E S S TO IMPROVE CORROSION RESISTANCE OF STEEL PARTS

H.S. Nayar a n d T. Philips, (Airco Gases, Murray Hill, New Jersey, USA). T h e d e v e l o p m e n t of a c o n t i n u o u s a t m o s p h e r e sintering furnace to provide a black oxide surface finish to sintered steel p a r t s was described. The oxide layer confers increased corrosion resistance on t h e steel parts. Data on p r o p e r t i e s was reported. ROLE OF FERROALLOY POWDERS IN IMPROVING THE PROPERTIES OF F E R R O U S PM PARTS

D.S. Madan, (Elkem Development Center, Pittsburg, Pennsylvania, USA). A t t e n t i o n was drawn to t h e need for PM materials ofimproved quality a n d it was suggested t h a t this could be achieved by the use of h i g h q u a l i t y Fe a n d ferroalloy powders. The study evaluated t h e role of ferroalloy powders d u r i n g sintering of Fe base parts, t h e properties of powders a n d parts being assessed. Examples using ferrophosphorus and ferroboron were considered a n d it was shown t h a t w h e r e high quality ferroalloy powders were used, parts with improved properties were obtained. E F F E C T OF POST-SINTERING COOLING ON THE PROPERTIES OF LOW ALLOY S T E E L S

M.L. Gagne a n d Y. Trudel, (Quebec Metal Powders, Montreal, Quebec, C a n a d a ) . Research into t h e effect of cooling rate, from the sintering temperature, on m e c h a n i c a l p r o p e r t i e s of Fe-base alloys w i t h a d d i t i o n s of C, Ni a n d Cu w a s reported. Specimens were sintered at 1120°C a n d c o o l e d a t v a r i o u s r a t e s between a n oil q u e n c h a n d a furnace cool. Strength, h a r d n e s s a n d i m p a c t resistance were m e a s u r e d with regard to cooling rate. Sinter hardened and austempered specimens were also tested.