The effect of the Si content upon bulk and intergranular diffusion in the 16Cr-14wt%Ni austenitic stainless steel was studied by using the residual activity method. The highest intergranular diffusion rate and the lowest activation energy for the component elements of the basic solid solution were found for 1wt%Si. The expressions for the bulk diffusion of 51Cr were:

0.1wt%Si:     D (cm2/s) = 6.8 x 10-2 exp[-251(kJ/g-atom)/RT]

1wt%Si:     D (cm2/s) = 8.6 x 10-2 exp[-251(kJ/g-atom)/RT]

4wt%Si:     D (cm2/s) = 1.2 x 10-1 exp[-251(kJ/g-atom)/RT]

The expressions for the grain-boundary diffusion of 51Cr were:

0.1wt%Si:     D (cm3/s) = 2.5 x 10-7 exp[-193(kJ/g-atom)/RT]

1wt%Si:     D (cm3/s) = 5.7 x 10-8 exp[-172(kJ/g-atom)/RT]

4wt%Si:     D (cm3/s) = 1.4 x 10-3 exp[-276(kJ/g-atom)/RT]

This behavior was explained in terms of a modification, of the interfacial energy, induced by Si segregation.

W.Assassa, P.Guiraldenq: Metal Science, 1978, 12[3], 123-8

Table 84

Grain Boundary Diffusion Parameters for Fe-18Cr-10Ni