The effect of ageing at 973 K on stress corrosion cracking of type 304 stainless steel

Stress corrosion cracking (SCC) behaviour of a Type 304 stainless steel aged at 973 K for various times was studied in boiling MgCl2 solution at free corrosion potential using constant load and slow strain rate methods. The SCC resistance of the steel was found to improve on ageing. Scanning electron microscopic observation of the fracture surfaces revealed transgranular to intergranular transition in cracking mode in the solution annealed steel. Ageing of the steel was found to inhibit the above transition, when the SCC test was conducted in MgCl2 solution boiling at 428 K. The absence of intergranular mode of SCC in aged steel is attributed to the sequestering of grain boundary phosphorus by the carbides precipitated at the boundaries and also to the homogenisation of slip by the carbides precipitated in the matrix. Copyright (C) 1996 Published by Elsevier Science Ltd.