The effect of tritium on the low temperature yield stress of niobium
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HYDROGEN P A R T I A L PRESSURE ( MPo obs ) 3 4 5 s 9 s 9 ,o ,, ,2 ' ! ~i/' ~'; ' ' " ' ' ' , , IOOhr Io 900/~" 4 0 0 ~ 2
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f o r m a t i o n f r o m that of m o l e c u l a r h y d r o g e n f o r m a t i o n . The low t e m p e r a t u r e high p r e s s u r e h y d r o g e n r a n g e has b e e n e x p e r i m e n t a l l y e x p l o r e d by R. H. C a v e t t and H. C. Van N e s s , 7 D. D. P e r l m u t t e r and B. F . Dodge 8 and H. C. Van N e s s and B. F. Dodgeo 9 U n f o r t u n a t e l y the data of t h e s e a u t h o r s can not be used f o r a v e r i f i c a t i o n of the low t e m p e r a t u r e a c t i v a t i o n e n e r g y . It m u s t be e m p h a s i z e d that the data u s e d f o r e v a l u a tion a r e f r o m d i f f e r e n t s o u r c e s r e p r e s e n t i n g s t e e l s of d i f f e r e n t o r i g i n , f a b r i c a t i o n h i s t o r y and s e r v i c e h i s t o r y . T h e r e f o r e , they cannot be u s e d to c a l c u l a t e a d e f i n i t e life e x p e c t a n c y . H o w e v e r , the e v a l u a t i o n has shown that the o p e r a t i n g r a n g e e x p r e s s e d by the N e l s o n c u r v e s e n c o m p a s s e s a t e m p e r a t u r e and p r e s s u r e r a n g e in which two d i f f e r e n t m e c h a n i s m s of d a m a g e a r e o p e r a tive o
2000
Fig. 2 - T i m e f o r h y d r o g e n a t t a c k of c a r b o n s t e e l a s a f u n c t i o n of t e m p e r a t u r e and h y d r o g e n p a r t i a l p r e s s u r e .
c a l / m o l e , a constant C = 1.298 x 10 -3~ f o r p r e s s u r e in psi or C = 8.943 • 10 -36 for p r e s s u r e in M P a and a t r a n s i t i o n t e m p e r a t u r e of 268~ This t e m p e r a t u r e c o m p a r e s f a v o r a b l y with that p o s t u l a t e d by P o d g u r s k i for s e p a r a t i o n of the t e m p e r a t u r e r e g i m e of m e t h a n e
1 H.H. Podgurskl: Trans. TMS-AIME, 1961. vol 221, pp. 389-94. 2. L. C. Wemer: Corroston, 1961, vol. 17, pp. 137-43 3 G. A Nelson Proc. Amer. Petr. lnst, 1965, vol. 45 diD, pp. 190-95. See also: Amer. Petro. Inst. Publ. 941, July 1970 4. R E Allen, R J. Jansen, P. C. Rosenthal, and F. H Vxtovec:Proe. Amer. Petr. Inst., 1962, vol. 42 diD, pp 452-62. 5. P. G. Shewmon' Met Trans. A, 1976, vol. 7A, pp 279-86. 6. H Schenk and H Taxhet" Arch. Eisenhuettenw, 1959. vol 30, pp. 661-71. 7. R H. Cavett and H. C Van Ness. Weld. J., i963, vol 42, pp 316S-19S. 8 D D Perlmutter and B. F Dodge hid Eng. Chem., 1956, vol. 48, pp 885-93. 9 H C. Van Ness and B F Dodge Chem Eng. Progr., 1955, vol. 51, pp. 266-71.
The Effect of Tritium on the Low Temperature Yield Stress of Niobium
p r e d i c t e d f o r the a c t i v a t i o n e n e r g y f o r diffusion. N e v e r t h e l e s s , m e a s u r e m e n t s of the a c t i v a t i o n e n e r g y of d i f fusion of d e u t e r i u m in niobium do i n d i c a t e that Q H < Q
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