The diffusion of 14C was studied, at temperatures ranging from 760 to 1360K, by using the residual activity technique. The bulk diffusivity results could be described by the expression:

D (m2/s) = 7.91 x 10-6 exp[-186.20(kJ/mol)/RT]

At temperatures below 960K, the 14C segregated markedly in the near-surface layers. The depth profiles exhibited an inverted shape near to the surface. This was attributed to a strong affinity of C atoms for the sub-surface layers. The results were explained in terms of an interstitial diffusion mechanism.

Migration of Carbon in Incoloy-800 A.R.Paul, K.N.G.Kaimal, S.R.Dharwadkar: Materials Chemistry and Physics, 1998, 53[3], 189-94