Enhance corrosion resistance of 304 stainless steel using nanosecond pulsed laser surface processing

In this study, a novel strategy for nanosecond (ns) laser surface processing was designed to improve the corrosion resistance of commercial 304 stainless steel (304 SS). The influence of different ns-laser parameters on pitting corrosion resistance was systematically investigated. An optimal pitting potential of ∼887 mV, from the origin of 503 mV, was obtained at a laser power of 20 W and a beam size of 116 µm, which was superior to those treated by traditional laser methods. Based on the microstructure observations, it was found that the gradient structured 304 SS was produced by the remelting effect of ns-laser surface processing. Along the direction of laser irradiation, the modified microstructure was composed of ultrafine grains in the topmost surface layer, dislocation accumulations in the sublayer, and coarse grains with nanotwins in the matrix. Additionally, the mechanisms of improved corrosion resistance were also revealed. The experimental results demonstrated that the formation of gradient microstructure containing ultrafine grains was responsible for the exceptional corrosion resistance. It is expected that the advanced ns-laser surface processing will be applied on various metallic materials to meet the practical demands for high corrosion resistance across various industries.