Microstructure and fracture of 52100 steel
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s t e e l m o s t u s e d for b a l l and r o l l e r b e a r i n g s is the A I S I / S A E g r a d e 52100, a s t e e l c o n t a i n i n g n o m i n a l l y 1 pet C and 1.3 to 1.6 pct C r . A m i c r o s t r u c t u r e of fine s p h e r i c a l c a r b i d e s in a m a r t e n s i t i c m a t r i x is g e n e r a l l y p r o d u c e d by a u s t e n i t i z i n g a s p h e r o i d i z e d m i e r o s t r u c t u r e at 840 to 860~ oil quenching, and t e m p e r i n g at 160 to 180~ In view of the b e a r i n g a p p l i c a t i o n s of 52100 s t e e l , a n u m b e r of i n v e s t i g a t i o n s have r e l a t e d m i c r o s t r u c t u r a l f e a t u r e s to r o l l i n g cont a c t fatigue p e r f o r m a n c e . F o r e x a m p l e , f i n e r e a r b i d e s p r o d u c e i m p r o v e d b e a r i n g fatigue life, 1,2 oxide inclusion particles are significantly more detrimental to fatigue life than a r e s u l f i d e s , 3,4 and p r i o r a u s t e n i t i c g r a i n b o u n d a r i e s have b e e n a s s o c i a t e d with the i n i t i a tion of fatigue c r a c k s d u r i n g h e r t z i a n loading. ~ R o l l i n g c o n t a c t fatigue p r o d u c e s v e r y fine m i c r o s t r u c t u r a l c h a n g e s o b s e r v a b l e a s e t c h i n g e f f e c t s o b s e r v a b l e in the light m i c r o s c o p e . T h e s e e f f e c t s have a l s o r e c e i v e d c o n s i d e r a b l e a t t e n t i o n ~9 in 52100 s t e e l , m o s t r e c e n t l y in t r a n s m i s s i o n e l e c t r o n s t u d i e s 8,9 which c h a r a c t e r i z e d t h r e e t y p e s of s t r u c t u r e s r e s u l t i n g f r o m m a r t e n s i t e and c a r b i d e d e c a y u n d e r c y c l i c s t r e s s . A n o t h e r a r e a of i n v e s t i g a t i o n has b e e n the e v a l u a t i o n of h e a t t r e a t m e n t s that i n c o r p o r a t e p e a r l i t e a s the s t a r t i n g s t r u c t u r e for h a r d e n i n g r a t h e r than the s p h e r o i d i z e d s t r u c t u r e g e n e r a l l y u s e d f o r 52100 s t e e l . S t i c k e l s 1'1~ has shown that i s o t h e r m a l l y t r a n s f o r m i n g to p e a r l i t e o r b a i n i t e r e s u l t s in a f i n e r and m o r e uniform carbide distribution after austenitizing for hardening, and h a s e x a m i n e d the c o m p r e s s i v e flow s t r e s s and w o r k h a r d e n i n g of quenched and t e m p e r e d 52100 KOZO NAKAZAWA is Principal Research Officer, National Research Institute for Metals, Tokyo, Japan, and GEORGE KRAUSS is AMAX Foundation Professor at the Department of Metallurgical Engineering, Colorado School of Mines, Golden, CO 80401. Manuscript submitted September 9, 1977.
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with both p e a r l i t i c and s p h e r o i d i z e d i n i t i a l m i c r o s t r u c tures. AISI 52100 was s e l e c t e d for the p r e s e n t i n v e s t i g a tion in o r d e r to e v a l u a t e the e f f e c t s of a u s t e n i t i z i n g on f r a c t u r e of a c o m m e r c i a l high c a r b o
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