Corrosion of sintered austenitic stainless steel in ferric chloride solution

Corrosion of sintered austenitic stainless steel in ferric chloride solution

PM Effects of c o n d i t i o n s of m e c h a n i c a l alloying, h e a t t r e a t m e n t and e x t r u s i o n and nature of the C used on mechan...

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Effects of c o n d i t i o n s of m e c h a n i c a l alloying, h e a t t r e a t m e n t and e x t r u s i o n and nature of the C used on mechanical properties and microstructure of A1-A14C3 composites were investigated. Porous carbon black or e l e c t r o g r a p h i t e are r e p o r t e d to give t h e b e s t results. The i n t e g r a t e d r e g i m e of h o t p r e s s i n g , s i n t e r i n g a n d e x t r u s i o n is s h o w n t o improve the mechanical p r o p e r t i e s and microstructure.

Copper M I C R O S T R U C T U R A L S T U D Y OF M E T A L POWDER D E N S I F I C A T I O N U S I N G COLD I S O S T A T I C C O M P A C T I O N

M. Grosbras et al (University of Poiters, Poiters, F r a n c e ) , Revue de Metallurgie,

Vol 91, No 2, 1994, 305-316. (In French). It is reported t h a t image analysis has been used to study morphological a n d stereological parameters of p o w d e r c o m p a c t i o n using Cu-O,3wt%Cu and an oxide dispersion s t r e n g t h e n e d alloy, m a d e by internal oxidation of the Al in a Cu3wt%A1 alloy. Resin impregnation was used to fill p o r e s in t h e s a m p l e s b e f o r e m e a s u r e m e n t s of the volume fraction of the phases present, surface area and curvature of the pore/solid interface and mean linear intercepts of solid and pore, were made. Predicted and measured morphological p a r a m e t e r s are c o m p a r e d and it is deduced t h a t densification can be described by progressive shrinkage of t h e radius of curvature of the pores. Equations, derived from the results, linking volume fraction of solid and applied pressure, are presented. M A N U F A C T U R E OF TWO C O M P O N E N T A L U M I N I U M B R O N Z E S BY PM METHODS

J. Michalowski et al (Wojskowa Akademia Techniczna, Warsaw, Poland), Metal, Prosz-

kow, Vol 26, No 3/4, 1993, 61-69. Polish).

(In

The p a p e r p r e s e n t s the results of a study of two p h a s e aluminium bronzes m a d e from Cu, A1 and CuO powders. The process route included explosive consolidation.

Iron and steel

LITERATURE

REVIEW

s h i e l d of m i c r o c r a c k s w e r e f o u n d to p r o p a g a t e faster t h a n long cracks at low stress ratios. OXYGEN C O N T E N T A N D METALLOGRAPHY OF ATOMIZED STAINLESS STEEL POWDER

S. Unami, O. Furukimi (Kawasaki Steel Corp, Kawasaki, J a p a n ) , J. Japan Soc.

W.F. Wang (Nan-Tai College of Technology a n d Business, Tainan, Taiwan), Powder

Powder and Powder Metallurgy, Vol 40, No 6, 1993, 630-636. (In Japanese).

Metallurgy, Vol 37, No 1, 1994, 33-36.

The effects of additions of graphite and sintering t e m p e r a t u r e on the s t r e n g t h and t o u g h n e s s of Fe-I%Cr-O, 7%Mn-O.3%Mo steel p o w d e r c o m p a c t s were investigated. A tensile s t r e n g t h of 760 MPa is r e p o r t e d for a 0.9%C steel s i n t e r e d at 1275°C. Density, %C, inclusions and the p r o p o r t i o n of p r o - e u t e c t o i d c e m e n t i t e at grain boundaries are shown to be t h e s t r e n g t h controlling factors. Excessive Fe3C reduces s t r e n g t h at 1.2%C. Loss of C at high sintering t e m p e r a t u r e s reduces s t r e n g t h but with further increase in t e m p e r a t u r e inclusions are reduced and s t r e n g t h increases.

The production of 304L stainless steel powders by w a t e r atomization is described. It is r e p o r t e d t h a t the O c o n t e n t of t h e powder could be controlled by a d j u s t m e n t of material and process factors namely t h e Si and Mn c o n t e n t s of the melt and t h e m e a n s of making additions during melting. The thickness of the oxide layer and t h e i n t e r n a l O b o t h d e c r e a s e with bulk O content. O c o n t e n t of the particle core is l0 to 14% lower t h a n at the surface. C O R R O S I O N OF S I N T E R E D AUSTENITIC STAINLESS STEEL IN FERRIC CHLORIDE SOLUTION

E. Otero et al (Universidad Complutense, Madrid, Spain), Revista de Metall., Vol 29,

No 6, 1993, 356-361. (In Spanish). The corrosion behaviour of sintered and cast 340L stainless steel in FeC 1a solutions are c o m p a r e d before a n d after cold working and h e a t treatment. Effects of electrolyte concentration were also investigated. C H A R A C T E R I S T I C S OF A PM M O L Y B D E N U M S T E E L FOR VALVE SEAT INSERTS

A_ Fujiki, A. Ishibashi (Nissan Motor Co., Yokohama, Japan.) J. Japan Soc. Powder

and Powder Metallurg35, Vol 40, No 6, 1993, 585-588. (In Japanese). An investigation of mechanical properties of a PM steel with 5%Mo, 5%Ni, 5%Co a n d 6%Cr, f o r a p p l i c a t i o n as automotive valve seat inserts, is described. Laboratory tests and engine trials were used. Processing involved t r a n s i e n t liquid p h a s e sintering. The alloy is said to be suitable for use with leaded and lead free m o t o r fuels. SINTERING-DIFFUSION-BONDING T E C H N I Q U E FOR S T E E L P O W D E R S USING HOT ISOSTATIC PRESSING

F A T I G U E OF S I N T E R E D S T E E L

B. Cotterell et al (National University of Singapore, Singapore), Acta Metall. Mater.,

E F F E C T S OF G R A P H I T E A D D I T I O N S A N D S I N T E R I N G T E M P E R A T U R E ON P R O P E R T I E S OF S T E E L C O M P A C T S CONTAINING CHROMIUM AND MANGANESE

M. N a k a m u r a et al (Iwate University, Morioka, J a p a n ) , J. Japan Soc. Powder and

Vol 42, No 1, 1994, 99-104.

Powder Metallurgy, Vol 40, No 6, 1993, 589-592. (In Japanese).

It is reported t h a t the tip of a fatigue crack in a sintered steel branches as it p r o p a g a t e s and t h u s introduces a negative stress intensity factor which counteracts t h a t at the crack tip. At low stress ratio values the crack tip stress intensity factor can be less t h a n zero causing t h e crack tip to close and retard crack growth. Short cracks growing from pores do not have a

It is r e p o r t e d t h a t HIP had been applied to s i n t e r i n g - d i f f u s i o n - b o n d i n g of m u l t i c o m p o n e n t p a r t s m a d e from Fe, Fe-O, 8wt%C-2%Cu and 304L stainless steel. Use of HIP is r e p o r t e d to allow a t e m p e r a t u r e 200 to 300°C lower t h a n is required for conventional sinter-diffusion-bonding a n d resulted in near full density. Joints between dissimilar metals had brittle joints.

WEAR R E S I S T A N T S T E E L S M A D E BY POWDER METALLURGY

E. Dudrova, M. Kabatova (Slovak Academy of Sciences, Kosice, Slovak R e p u b l i c ) ,

Powder Metallurgy Science and Technology, Vol 4, No 4, 1993, 15-21. PM wear resistant steel is discussed with r e s p e c t to c o m p o s i t i o n , s t r u c t u r e a n d properties. Dispersion h a r d e n e d materials with an alloyed peariitic/carbide structure with a d d e d hard particles are considered. Activated sintering of M2 high speed steel with 8%Cu is discussed. S I N T E R I N G OF LOW ALLOY S T E E L S MADE FROM E L E M E N T A L P O W D E R S

H. D a n n i n g e r (Technical University of Vienna, Vienna, Austria), Powder Metallurgy Science and Technology, Vol 4, No 4, 1993, 22-36. It is n o t e d t h a t the use of elemental p o w d e r s may offer greater flexibility of composition due to b e t t e r consistency of r a w m a t e r i a l s t h a n is t h e c a s e w i t h prealloyed powders. The i m p o r t a n c e of h o m o g e n i z a t i o n d u r i n g s i n t e r i n g is e m p h a s i z e d a n d m e c h a n i s m s , diffusion, liquid p h a s e sintering and gas t r a n s p o r t are considered. E x a m p l e s are given with regard to steel with Cu, Mo, W a n d Cr and any combination. The need to avoid coarse secondary p o r e s is stressed. F A T I G U E CRACK GROWTH B E H A V I O U R IN SINTERED FERROUS MATERIALS

T. Yamaguchi et al (Kumamoto University, Kumamoto, J a p a n ) , J. Japan Soc. Powder

and Powder Metallurgy, Vol 40, No 7, 1993, 723-729. (In Japanese). Fatigue behaviour, under various c o n d i t i o n s , o f s i n t e r e d Fe a n d s t e e l c o m p a c t s and n o d u l a r cast iron are

MPR September 1994 51