The diffusion of hydrogen in liquid iron alloys
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N. A. D. PARLEE
Rates of absorption of hydrogen in stagnant liquid iron and ten (Fe-X) binary iron alloy systems were studied by an unsteady-state gas-liquid metal diffusion cell technique. These rates were found to be controlled by diffusion of hydrogen in the liquid phase. Chemical diffusion coefficients (/9H) were measured in pure iron and Fe-X alloys in the following (at. pct) composition r a n g e s : Mn (0 to 5), Cr (0 to 25), V (0 to 25), Nb (0 to 10), Mo (0 to 25), W (0 to 5), Ni (0 to 75), Co (0 to 75), Sn (0 to 10), and Cu (0 to 25). All m e a s u r e d D H values at 1600~ lie b e t w e e n 7 • 10 -4 and 16 x 10 -4 sq cm p e r sec. The diffusion c o e f f i c i e n t s found for p u r e i r o n can be r e p r e s e n t e d by D~ e = 4.37 • 10 -3 exp (-4134 + IO12)/RT cm2/sec w h e r e the u n c e r t a i n t y in the a c t i v a t i o n e n e r g y , Q, in cal p e r m o l e , c o r r e s p o n d s to the 90 pct confidence l e v e l . A l i n e a r r e l a t i o n s h i p was found between the l o g a r i t h m of the h y d r o g e n difFe -X and the i n t e r a c t i o n p a r a m e t e r ~rT X for low and m e d i u m c o n c e n t r a t i o n s fusion coefficient D H of a l l o y i n g e l e m e n t X , when applied to a fixed c o n c e n t r a f f o n of X(5 or 25 at. pct) and to i n d i vidual p e r i o d s in the periodic table. A u s e f u l l i n e a r c o r r e l a t i o n a l s o a p p e a r s to exist between log D Fe-X a n d hydrogen s o l u b i l i t y ' for fixed c o n c e n t r a t i o n of X and with r e s p e c t to the p e r i o d in which X is found.
E L - T A Y E B and P a r l e e 1 studied the r a t e s of a b s o r p tion of hydrogen in s t a g n a n t liquid i r o n u s i n g a g a s liquid diffusion cell t e c h n i q u e . They found t h e s e r a t e s to be c o n t r o l l e d by diffusion in the liquid and r e p o r t e d c h e m i c a l diffusion c o e f f i c i e n t s (DTM)for h y d r o g e n in p u r e i r o n , for the 1547 ~ to 1726~ t e m p e r a t u r e r a n g e , in the f o r m of a n A r r h e n i u s equation. Nyquist 2 applied a quenching method and r e p o r t e d a few D ~ e v a l u e s in the 1550~ to 1640~ t e m p e r a t u r e r a n g e . His DFe value for 1600 C is e s s e n t i a l l y the s a m e a s E I - T a y e b and P a r l e e ' s , but he m a d e too few m e a s u r e m e n t s at o t h e r t e m p e r a t u r e s to develop a r e l i a b l e A r r h e n i u s equation. R e c e n t l y Solar and G u t h r i e s r e p o r t e d the r e s u l t s of t h e i r own g a s - l i q u i d diffusion t e c h n i q u e , which y i e l d e d DH Fe values and an A r r h e n i u s equation s o m e w h a t but not g r e a t l y different f r o m E 1 - T a y e b and P a r l e e ' s work. A l l a u t h o r s concluded that the diffusion of hyd r o g e n in the liquid is the slowest step in the a b s o r p tion p r o c e s s for p u r e i r o n , and that diffusion coeffic i e n t s could be c a l c u l a t e d by the a p p l i c a t i o n of F i c k ' s Second La
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