Friction stir welding of grain boundary engineered 304 austenitic stainless steel

Abstract

“Weld decay” which is intergranular corrosion in the heat-affected zone is a conventional and momentous problem during welding of austenitic stainless steels. The intergranular corrosion is attributed to sensitization. Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels cannot be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment. It has been reported that grain boundary engineering is effective to suppress weld decay by increase in frequency of coincidence site lattice boundaries so as to disconnect random boundary network. Friction stir welding has been also confirmed to be effective to reduce the degree of sensitization in weld decay region due to small thermal affect. In this study, the simultaneous or synergy effect of the two technologies on prevention of weld decay was examined by friction stir welding of grain boundary engineered 304 austenitic stainless steel. The corrosion test demonstrated that the combination of grain boundary engineering and friction stir welding shows a significant suppression of weld decay.