Effect of surface machining on intergranular stress corrosion cracking (IGSCC) in sensitised type 304 austenitic stainless steel

The effect of surface finish, applied stress and test duration on the developed populations of short crack nuclei has been studied for a thermally sensitised type 304 austenitic stainless steel, exposed to acidified potassium tetrathionate (K2S4O6) solution. The crack populations can be quantified using extreme value statistics (Gumbel distribution) to obtain a characteristic crack length. The surface finish has a significant impact on crack development; a roughly machined surface, obtained with a greater depth of cut, is most susceptible to intergranular failure. The characteristic crack length of the crack population increases with tensile stress and test duration. Residual stress can cause cracking in the absence of an applied stress.