Laser surface modification to improve the resistance of CMAS + molten salt coupling corrosion to thermal barrier coatings

Abstract

In marine environment, thermal barrier coatings (TBCs) face coupling corrosion of calcium magnesium aluminum silicate (CMAS) and molten salt leading to premature failure. In this study, microstructure evolution of TBCs resulting from CMAS + NaVO3 (CN) coupling corrosion is investigated, and a corrosion protection method based on laser glazing is proposed. TBC degradation by the CN coupling corrosion is mainly due to the high penetration ability of the melt. Laser glazed TBCs have improved resistance to the coupling corrosion, however, the vertical cracks in the glazed layer provide paths for melt penetration. TBCs with double laser-glazed layer are designed, with vertical cracks in the glazed layer being bifurcated and staggered, which could largely suppress CN melt infiltration, and also exhibits excellent phase and microstructure stability in the coupling corrosion condition. This type of laser modified TBC is confirmed to be attractive against the coupling corrosion.