Early-stage mechanistic insights into vanadium-induced hot corrosion of yttria-stabilized zirconia thermal barrier coatings

Vanadium-induced hot corrosion is a critical threat to the durability of yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) under transient conditions such as gas turbine start-up. This study investigates the early-stage degradation of 8YSZ powders exposed to 5 wt% V₂O₅ at 900°C for 60 min and characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) equipped with energy-dispersive spectroscopy (EDS). Results show rapid tetragonal-to-monoclinic phase transformation, with the monoclinic fraction increasing from 3.7 % in the untreated state to 76.7 % after 60 min. This transformation is driven by yttrium depletion via YVO4 formation, as confirmed by microstructures and compositions. Shifts in diffraction peak positions and the appearance of Y-depleted zones further support a progressive degradation mechanism. By quantifying phase evolution over short exposure time, new kinetic insight into the onset of vanadium-induced corrosion and establishes a mechanistic basis for early-stage failure prediction and mitigation in advanced thermal barrier systems.