Femtosecond laser polishing yttria-stabilized zirconia coatings for improving molten salts corrosion resistance

•Improvement of hot corrosion behavior of YSZ coating by femtosecond laser polishing.•Reduction of roughness from Ra 6.615 μm to Ra 1.562 μm by laser polishing.•Voids healing occur due to volume absorption and multiple reflections of laser.•Removal of pores and polished surface retard leaching of Y and in-diffusion of V.•These two factors are jointly responsible for hot corrosion improvement of APS TBCs. In this study, we present a novel method of polishing thermal barrier coatings' surface using high-frequency femtosecond laser. Compared to the conventional mechanical micro-grinding, light trapping due to multiple reflection from porous-structure, which enhances its coupling into coating, resulted in desired effect of healing of the voids in performing a layer-by-layer laser ablation. Herein, the corrosion resistances of these coatings subjected to Na2SO4+V2O5 at 1000 °C was investigated. Three observed transport behaviors: (i) molten salts infiltration, (ii) Y-leaching, and (iii) V-in-diffusion, are discussed to illustrate corrosion mechanisms. Laser-polished coatings with smooth surface and healed voids show superior molten salts resistance and significantly alleviate leaching or in-diffusion of elements.