Tracer diffusion of 59 Fe and 51 Cr in Fe-17 Wt Pet Cr-12 Wt Pet Ni austenitic alloy
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a t o m i c t r a n s p o r t of i r o n , c h r o m i u m , and n i c k e l in the a u s t e n i t i c alloy F e - 1 7 wt pct C r - 1 2 wt pct Ni b y both l a t t i c e and g r a i n - b o u n d a r y diffusion has b e e n s t u d ied u s i n g r a d i o a c t i v e t r a c e r t e c h n i q u e s . R e s u l t s of the nickel i n v e s t i g a t i o n have b e e n p r e v i o u s l y r e p o r t e d . 1 The r e s u l t s of the i r o n and c h r o m i u m i n v e s t i g a t i o n s a r e p r e s e n t e d h e r e , and the r a t e s of diffusion of the t h r e e e l e m e n t s a r e c o m p a r e d . P a r a m e t e r s f r o m the A r r h e n i u s - t y p e equation, D = D Oexp [ - Q / R T ], for v o l ume and g r a i n - b o u n d a r y diffusion of i r o n and c h r o m i u m in p u r e g a m m a i r o n and in a u s t e n i t i c s t e e l s obtained by s e v e r a l i n v e s t i g a t o r s a r e s u m m a r i z e d in Table I. A s i m i l a r s u m m a r y for n i c k e l was made e a r l i e r . ~ The p u r p o s e of this i n v e s t i g a t i o n is to aid in the u n d e r s t a n d ing of diffusion of m a j o r c o n s t i t u e n t s in a u s t e n i t i c s t a i n l e s s s t e e l s , in p a r t i c u l a r in type 316 s t a i n l e s s steel.
EXPERIMENTAL The s p e c i m e n s f r o m the s a m e b a r of m a t e r i a l p r e v i o u s l y used w e r e p r e p a r e d and p o l i s h e d in the m a n n e r p r e v i o u s l y d e s c r i b e d . 1 The r a d i o a c t i v e SlCr and 59Fe t r a c e r s w e r e deposited onto the s p e c i m e n s e i t h e r d r o p wise o r by e v a p o r a t i o n under a v a c u u m , and the s p e c i m e n s w e r e s e a l e d in q u a r t z a m p o u l e s for the diffusion a n n e a l s . 1 A n n e a l s for each isotope r a n g e d f r o m 600 to 1300~ at a p p r o x i m a t e l y 50~ i n t e r v a l s . Volume diffusion of the r a d i o a c t i v e t r a c e r was a n a l y z e d for s p e c i m e n s over the e n t i r e t e m p e r a t u r e r a n g e , and g r a i n b o u n d a r y diffusion was a n a l y z e d for s p e c i m e n s f r o m 600 to 1050~ After its diffusion a n n e a l , each s p e c i m e n was s e r i a l s e c t i o n e d to a n a l y z e the v o l u m e diffusion p r o f i l e by lathe m a c h i n i n g , hand g r i n d i n g or s p u t t e r i n g depending upon the width of the v o l u m e diffusion zone. The r a d i o f r e q u e n c y s p u t t e r i n g technique which a l lows the r e m o v a l of v e r y thin s e c t i o n s has b e e n d e v e l -
R. A. PERKINS, formerly Presidential Intern in the Metals and Ceramics Division,Oak Ridge National Laboratory, is with GlobeUnion, Inc., Milwaukee,Wis. 53201. R. A. PADGETr, Jr., is Technologist in the Metals and Ceramics Division,Oak Ridge National Laboratory, Oak Ridge, Tenn. 37830. N. K. TUNALI is with the Middle East Technical University, Ankara, Turkey. Manuscript submitted January 10, 1973. METALLURGICALTRANSACTIONS
Table I. Volume and Grain Boundary Diffusion
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