The effect of excimer laser surface treatment on pitting corrosion resistance of 316LS stainless steel

Excimer laser surface treatment of 316LS bio-grade stainless steel (ASTM-F138) was conducted with the aim of enhancing the pitting corrosion resistance of the material. The experiment was performed under two different gas environments: air and nitrogen. The microstructure, phase and compositional changes after laser treatment were characterized by means of XRD, XPS and EDX; the resulting pitting corrosion resistance was evaluated by electrochemical polarization tests. The results show that excimer laser surface melting can effectively eliminate carbides and second phases alike, and also serves the function of homogenizing the microstructure. Nitrogen induced into the laser-treated surface could promote new precipitates and as a result lowered the corrosion resistance. On the other hand, laser treatment in a low partial pressure of nitrogen could enhance the corrosion resistance of 316LS stainless steel in that the active corrosion current was reduced and the passive range was widened.