Solubility of graphite in cobalt and nickel
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T a M e I . C a r b u H z a t i o n T r e a t m e m u and Resul~
Temperatu~,~ 1126 1173 1173 1275 1392 1392 1393 1425
0.910 0.823 0.982 0.925 0.984 0.641 0.387 0.136
0.090 0.104 0.116 0.210 0.430 0.290 0.176 0.074
Nickel
1124
0.881
1126 1272 1392 1450 1469 1477
0.910 0.932 0.641 0.503 1.0 1.0
10.093 [0.102 0.126 0.190 0.220 0.200 0.387 0.439
DURINGthe
log ac/Y c = A + B / T + C(1 + lOS/T)yc
*The activityis defined as unity for equilibriumwith graphite.
1200 ' 1
2.5
I
1000
900=C
' [
'
[1]
w h e r e Yc is the a t o m r a t i o , T i s t h e a b s o l u t e t e m p e r a t u r e and A , B , and C a r e t e m p e r a t u r e and c o m p o s i t i o n independent parameters), Smith's data determine C = 2.5 a n d 5.3 f o r Co(C) a n d Ni(C), r e s p e c t i v e l y . S i n c e the l a s t t e r m in E q . [1] is r e l a t i v e l y s m a l l , its c h o s e n t e m p e r a t u r e d e p e n d e n c e is not i m p o r t a n t f o r the p r e s e n t c o n c l u s i o n s . F i g . 1 d i s p l a y s log ac/Yc - C(1 + 103/T)Yc vs T -x f o r the p r e s e n t d a t a and t h o s e of S m i t h . L e a s t s q u a r e s a n a l y s i s of the p l o t t e d d a t a d e t e r m i n e the f o l l o w i n g equations : log ac/Y c = 4110/7" - 1.34 + 2.5(1 + 103/T)Yc
An~ysis, WtPct C
Cob~t J . C. S W A R T Z c o u r s e of e x p e r i m e n t s 1 on the e l e c t r i c a l r e s i s t i v i t y of c a r b o n d i s s o l v e d in c o b a l t and n i c k e l , s e v e r a l m e a s u r e m e n t s of the s o l u b i l i t y of g r a p h i t e were obtained. This report summarizes these measu r e m e n t s and d i s c u s s e s the s o l u t i o n e n e r g i e s a n d entropies. T h i n s a m p l e s of high p u r i t y c o b a l t and n i c k e l w e r e e q u i l i b r a t e d w i t h c a r b u r i z i n g g a s e s by the u s u a l t e c h n i q u e s . 2 T a b l e I l i s t s the a c t i v i t y of e a c h c a r b u r i z i n g a t m o s p h e r e 3 and the r e s u l t i n g c o m b u s t i o n a n a l y s i s . To c o l l a t e t h e s e data o n e m u s t a s s u m e s o m e b e h a v i o r r e l a t i v e to H e n r y ' s l a w . S m i t h ' s d a t a 4 on Co(C) and Ni(C) at 1000~ show d e v i a t i o n s f r o m H e n r y ' s law w h i c h a r e c o m p a r a b l e to t h o s e of y F e ( C ) . A s s u m i n g t h e s e d e v i a t i o n s v a r y w i t h t e m p e r a t u r e Uke t h o s e of Y F e ( C ) ( i . e . , a s s u m i n g a r e l a t i o n of t h e f o r m : s
Acti~ty Rel. to Graphite*
y
3'0
f ,
=,? -
m
.~ 2.0
-
-
o,i u
o
2.5 %
I
--
%
k5
2.0 o
[2]
f o r c a r b o n in c o b a l t , and 1
logac/Y c = 3070/7 -0.54
+ 5.3(1 + 103/T)Yc
[3]
7
I
8 104/T,
f o r c a r b o n in n i c k e l . F i g s . 2 and 3 c o m p a r e t h e g r a p h i t e s o l u b i l i t i e s f r o m E q s . [2] and [3] w i t h o t h e r r e c e n t d e t e r m i n a t i o n s . E q s . I2] and [3] and t h e e q u i v a l e n t e q u a t i o n f o r 7 F e ( C ) d e t e r m i n e the v a l u e s in T
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