The tracer diffusivity of 14C in austenitic alloys, where the Cr content ranged from 0 to 70at% and the Fe content ranged from 0 to 32at%Cr, was studied at temperatures of between 823 and 1123K (table 192) by using a serial sectioning method. It was found that, with increasing Fe and/or Cr content, the diffusivity decreased and the Arrhenius parameters increased. The compositional dependence of the diffusional characteristics was explained in terms of the trapping effects of Fe and Cr. Local maxima in the pre-exponential factor and activation energy near to the composition, Ni3(Cr,Fe), were attributed to the effect of a short-range ordering of substitutional atoms. A maximum of the C diffusivity, near to 40at%Fe, in the Ni-Fe system was suggested to be due to a minimum in the interaction between C and substitutional atoms.

J.Cermák, H.Mehrer: Acta Metallurgica et Materialia, 1994, 42[4], 1345-50

Table 185

Permeability of H in IN718

ac: air-cooled, fc: furnace-cooled