Unsatisfactory CMAS resistance of Gd2Zr2O7 thermal barrier coatings and the solution strategy based on laser surface modification

Abstract

Gd2Zr2O7 thermal barrier coatings (TBCs) were reported to be resistant to calcium-magnesium-aluminum-silicon (CMAS) corrosion, but is still unsatisfactory. In this study, laser surface modification is employed to further improve CMAS resistance of Gd2Zr2O7 coatings. The modification layer consists of a columnar microstructure, which is affected by the modification parameters such as pulse width and beam length. CMAS corrosion resistance of the as-fabricated and laser modified Gd2Zr2O7 coatings is compared. At 1250 °C for 1 h, a reaction layer forms between the Gd2Zr2O7 coating and CMAS which has some ability to suppress molten CMAS penetration. After prolonged corrosion (4 and 10 h), however, the reaction layer continues to thicken until no CMAS remains, which largely consumes the coating thickness and degrades the coating performance. Laser surface modification has solved this problem effectively due to its ability to reduce the melt penetration channels. Hence, laser-modified Gd2Zr2O7 coatings have enhanced CMAS resistance.