The hot corrosion resistance of APS YSZ coatings micro glazed via an ultraviolet picosecond ultrashort pulsed laser

Abstract

In this paper, yttria-stabilized zirconia (YSZ) was innovatively glazed via an ultraviolet picosecond ultrashort pulsed laser (laser micro glazing, LMG). A smooth LMGed layer (surface roughness: ∼0.714 µm) with incredibly narrow cracks (< 0.547 µm in width) was achieved. The hot corrosion tests of molten salt (V2O5 +Na2SO4) at 1100 °C for 20 h were performed. The results show that laser irradiation not only increased oxygen vacancies but also reduced the reaction area between the molten salt and coatings. During the hot corrosion test, the LMGed layer with ultra-fine grains also promoted a homogeneous redistribution of Y3+ during the segregation process. These factors greatly improved the phase and structural stability of t′-ZrO2 in the LMGed surface. Interestingly, the self-healing phenomenon of narrow cracks was found in the LMGed layer, which tremendously decreased the penetration channels of the molten salt. Compared with the original as-sprayed coatings, the corrosion product YVO4 on the LMGed coatings was not only reduced in number but also greatly diminished in size. Meanwhile, the m-ZrO2 content and penetration depth in the LMGed coatings were decreased by 80.336 % and 60.057 %, which demonstrated the excellent hot corrosion resistance of LMGed YSZ coatings.