Hot corrosion behaviours of the LaYbZr₂O₇ thermal barrier coatings in different corrosive salts

Abstract

In this study, the LaYbZr2O7 (LYZ) thermal barrier coatings (TBCs) were deposited by air plasma spray (APS) and were subjected to hot corrosion in the single V2O5 salts and the mixture of V2O5+Na2SO4 with different Na2SO4 content at 1000 °C. The reaction mechanism and corrosion layer evolution of the LYZ coating in different corrosive molten were comparatively investigated. After hot corrosion in the single V2O5 salt, the surface of the LYZ coating develops a dense corrosion layer, which could keep structural integrity with the extension of exposure time, indicating the LYZ coating showed higher resistance to the V2O5 corrosion. However, the dense layer failed to form on the surface of the LYZ coating in the V2O5+Na2SO4 mixed salts. With the increase of Na2SO4 content, the corrosion products formed on the surface of the LYZ coating gradually decreased, and the corrosion layer disappeared. The dominant reason for the difference was that the addition of Na2SO4 resulted in the acidity reduction of the mixed salts, which eventually caused a decrease in the corrosion rate. Compared with the single V2O5, the V2O5+Na2SO4 mixed salts showed higher penetration ability in the LYZ coating and could be more damaging.