Corrosion behavior of nanostructured ferritic stainless steel by the generation of LIPSS with ultrashort laser pulses

Femtosecond ultra-short laser pulses can induce various micro- and nanostructural changes in the surface of stainless steel, paving the way for new functionalities in the application of these materials. In this work, UV, visible, and IR femtosecond laser pulses have been utilized on ferritic stainless steel under differing conditions of fluence, pulses per spot and hatch distance. These variables resulted in various compositional and micro- and nanostructural changes on the steel surfaces. The texturing processes which originate these changes can be meticulously designed by selecting the appropriate strategy and laser parameters, leading to Laser-Induced Periodic Surface Structures (LIPSS) and other potential morphologies. A significant problem to consider during the laser treatment of stainless-steel surfaces is the effect that these microstructural modifications, induced by the ultra-short pulses, can have on the corrosion behavior and the brightness of the surface. On one hand, a detailed study of the effect that these treatments can have on the corrosion resistance of the stainless steel under investigation has been conducted. The study shows that under specific conditions, treatments with ultra-short laser pulses maintain the corrosion resistance of the surfaces. On the other hand, the study of the surface brightness after laser treatments, as measured by the Light Reflectance Value (LRV), shows that brightness is only slightly decreased (less than 10 %) for samples where Surface Density of Applied Energy (SDAE) is lower than 2 J/cm2. Furthermore, the diffuse LRV is increased in every textured sample due to the presence of ripples.