Effect of laser surface cleaning of corroded 304L stainless steel on microstructure and mechanical properties

In this study, a high-power Nd:YAG laser is used to remove a corrosion layer on the surface of 304L stainless steel (SS304L). A laser power of 1140 W with different hatch distances and the number of repetitions is employed for corrosion removal. As shown by an electron probe X-ray microanalyzer, corrosion removal is successfully achieved via laser surface cleaning (LSC) with the small hatch distance or the large number of repetitions. However, corrosion residues remain at the surface of SS304L after the LSC process with the large hatch distance and the small number of repetitions. The effect of LSC process on the microstructure and mechanical properties of SS304L is investigated. The electron backscatter diffraction and transmission electron microscopy analyses reveal that the microstructure of SS304L depends significantly on the LSC conditions. In the LSC process with the large hatch distance and the small number of repetitions, only an increase in dislocation density is discovered. However, the LSC process with the small hatch distance or the large number of repetitions introduces dense dislocation structures, deformation twins, grain refinement, and precipitation. This microstructural alteration owing to the LSC process modifies the mechanical properties of SS304L in terms of hardness and tensile strength.