Ultraviolet picosecond ultrashort pulsed laser micro glazed EB-PVD YSZ coatings for improving the molten salt (Na2SO4 + V2O5) corrosion resistance

In this study, yttria-stabilized zirconia was glazed for the first time using an ultraviolet picosecond ultrashort pulse laser (laser micro glazing, LMG). A smooth LMGed layer (surface roughness: ∼1.4 μm) with extremely narrow cracks (width: < 0.6 μm) was fabricated on the surface to resist molten salt corrosion. The hot corrosion resistance of LMGed coatings was systematically investigated. Two models of corrosion behavior were observed from the results: (І) widespread but slow corrosion of columnar crystals, and (II) rapid but little penetration in defects (inter-columnar gaps, and cracks). The thermal stabilization of the LMGed layer was greatly improved due to the positive effects of grain refinement on elevating oxygen vacancies and more uniform redistribution of Y3+. The content of YVO4 and m-ZrO2 on the LMGed coatings was significantly reduced compared to the non-LMGed coatings. The self-healing of narrow cracks under prolonged high temperatures resulted in slow and slight penetration of the molten salt along the grain boundaries. No visible grey YVO4 was observed throughout the interior, demonstrating the positive role of LMG technology in enhancing hot corrosion resistance.