Stress corrosion crack propagation in AISI 304 stainless steel weldment

The effect of δ-ferrite in the AISI 304 austenitic stainless steel weldment on the stress corrosion crack propagation in boiling MgCl2 solution was investigated. The network structure of δ-ferrite retarded the crack propagation rate due to keying effect, and the crack propagation along the boundaries of γ and δ-ferrite phases. However, the crack propagation rate of the weldment was even faster than that of the matrix when dissolved nitrogen content was so high that there was no δ-ferrite in the weldment. Comparing with the previously published paper, we found that the predominant factor determining the stress corrosion cracking life time was not the time for crack initiation, but the crack propagation rate. Application of the linear fracture mechanics to stress corrosion cracking was also discussed briefly. (Author)