Temper embrittlement in a Ni-Cr steel containing phosphorus as impurity
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has been known at l e a s t f o r the l a s t twenty y e a r s that p r e s e n c e of p h o s p h o r u s , even in t r a c e a m o u n t s , c o n t r i b u t e s to t e m p e r e m b r i t t l e m e n t in low alloy s t e e l s . 1 Since the f r a c t u r e due to e m b r t t t l e m e n t a l w a y s o c c u r r e d along p r i o r a u s t e n i t e g r a i n b o u n d a r i e s , s e g r e g a t i o n of p h o s p h o r u s to t h e s e b o u n d a r i e s was s u s p e c t e d to be o c c u r r i n g , a r e s u l t i n g in a g e n e r a l w e a k e n ing of the i n t e r f a c e s . S i m p l e s e g r e g a t i o n of p h o s p h o r u s 2 as w e l l as f o r m a t i o n of a s e c o n d p h a s e phosphide 3'4 at g r a i n b r o u n d a r i e s w e r e s u g g e s t e d to be o p e r a t i v e . A l l t he s e p o s t u l a t e s r e m a i n e d m e r e l y s p e c u l a t i v e in n at u r e f o r a long t i m e , s i n c e v a r i o u s a t t e m p t s to identify a s e g r e g a t e o r p r e c i p i t a t e at the a u s t e n i t e b o u n d a r i e s of t e m p e r - e m b r i t t l e d s p e c i m e n s w e r e u n s u c c e s s f u l . S-7 Two s t u d i e s , h o w e v e r , m e t with p a r t i a l s u c c e s s . By c h e m i c a l et ch i n g of the i n t e r g r a n u l a r f r a c t u r e s u r f a c e of an e m b r i t t l e d N i - C r s t e e l , f o l l o w e d by w e t c h e m i c a l a n a l y s i s , A r k h a r o v 8 d e m o n s t r a t e d that the c o n c e n r a t i o n of p h o s p h o r o u s was 1.7 t i m e s the bulk c o n c e n t r a t i o n . He f ai l ed , h o w e v e r , to show that such a condition was a b s e n t in a n o n e m b r i t t l e d s a m p l e . The second study was by Inman and T i p l e r , ~ who, by m e a s u r i n g the r a d i o a c t i v i t y of the e tc h i n g p r o d u c t , found p h o s p h o r u s s e g r e g a t e d to g r a i n b o u n d a r i e s to an e q u i v a l e n t depth of 30 to 60A of p u r e p h o s p h o r u s a f t e r a 10 rain t r e a t m e n t of 1300~ of i r o n doped with 0.09 wt pet r a d i o a c t i v e p h o s p h o r u s . The e x c e s s i v e a m o u n t of p h o s p h o r u s found to be s e g r e g a t e d in t h e i r s t e e l , was c o n s i d e r e d to be i n c o m p a t i b l e with an e q u i l i b r i u m s e g r e g a t i o n p r o c e s s , and hence, Cahn and H i l l i a r d 1~ s u g g e s t e d that the p h o s p h o r u s m u s t be p r e s e n t as a p r e c i p i t a t e p h a s e at the g r a i n b o u n d a r i e s . Significant a d v a n c e s w e r e m a d e in 1968, in d e m o n s t r a t i n g s e g r e g a t i o n of p h o s p h o r u s in s t e e l s , with the advent of the Au g e r e l e c t r o n e m i s s i o n s p e c t r o s c o p y , h e r e a f t e r r e f e r r e d to as A u g e r a n a l y s i s . Although the A u g e r e f f e c t was known as e a r l y a s 1925, the f i r s t a t t e m p t to apply it to m e t a l l u r g i c a l p r o b l e m s w as
made in 1968 by Harris. n'12 H
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