Diffusion was measured in the low-alloy (3335 series) ferritic steel (3Ni-0.78Cr-0.65wt%Mn) at 673 to 873K; where a temper embrittlement effect took place. The HIRBS technique was used. The results were compared to previous ones obtained in pure α-Fe. The Sb diffusivities were higher than that of Fe self-diffusion. The results (table 146) could be described by:

D (m2/s) = 5 x 10-5 exp[-233(kJ/mol)/RT]

All of the impurity diffusion coefficients lay in a narrow band, along the measured temperatures, both in the pure α-Fe structure (large grain size) and in the martensitic-like morphology of the steel. The HIRBS technique revealed the true bulk diffusion coefficients in these matrices and the influence upon the diffusivity of the various elements.

D.N.Torres, M.J.Iribarren, R.A.Pérez, F.Dyment: Materials Letters, 2006, 60[3], 301-4

Table 147

Bulk Diffusivities of Sn in 3335 Steel