Microstructural evolution and corrosion responses of friction stir welded SUS301L stainless steel

As a typical manifestation of elemental segregation of stainless steel, chromium depletion was often brought about by welding, leading to undesirable corrosion resistance. In light of this, we employed friction stir welding through WC -W composite welding tools to achieve sound joints of SUS301L stainless steel, with corrosion resistance exceeding that of the base material (BM). A higher austenite fraction of 20.8% enhanced corrosion resistance since the corrosion potential of austenite is nobler than that of martensite. Austenite was not decomposed into harmful a-phases due to the shorter holding time at the elevated temperature, thus enhancing the homogeneity of the microstructure. The ultimate tensile strength of the welded joints reached 820 MPa, which was equal to 98.9% of BM. The pitting potential of the joint was increased by 0.078 V, indicating that the stability of the passive films was improved, and the ability to resist the corrosive medium was strengthened. Chromium depletion was eliminated, resulting in no sensitivity to intergranular corrosion.