Nanosecond multi-passes laser surface texturing on AISI 301LN TRIP steel

Laser surface texturing is a promising technique for improving the surface properties of metals. In this study, a nanosecond pulsed laser was used to perform surface texturing on a metastable austenitic stainless steel AISI 301LN. The effects of the number of laser passes (from 1 to 1000 passes) on the surface morphology, microstructure, and mechanical properties were investigated. The results show that the depth of laser tracks increases with the number of passes due to thermal accumulation. Increasing the number of laser passes produces a rougher surface, but beyond a certain value, a smoother texture is observed. The amount of α’-martensite phase induced by the laser increases with the number of passes, producing augments in hardness. However, again, this trend changes after a certain number of laser passes, and hardening saturates and even decreases. Therefore, selecting the appropriate laser processing parameters and number of passes is essential to control the dimensions of laser tracks and thus the desired surface texture and also to achieve the level of hardening.