TRACER DIFFUSION OF CARBON IN FE-NI-CR-C ALLOYS

The diffusivity of C-14 in austenitic alloys Fe-19at.%Ni-11at.%Cr-xC (x=0.010, 0.047, 0.065, 0.130, 0.288 and 0.809 at.%) has been studied in the temperature interval from 773 to 1023 K using a serial sectioning method. It appears that the carbon diffusion coefficients D increase with increasing average carbon concentration in accordance with an analogous dependence reported in the literature for the case of non-alloyed austenite Fe-C. The variation in the diffusion characteristics with the composition is explained in terms of C trapping by Cr atoms, and in terms of a repulsive interaction between nearest-neighbour C pairs. An empirical relation for calculation of D at various temperatures and carbon concentrations is proposed.