LAUSR

Abstract The initial stage of degradation process of yttria partially stabilized zirconia thermal barrier coatings during heating at 1000–1450 K were observed in situ by transmission electron microscopy. The observation directly demonstrated that the formation of several kinds of oxides and resulting void growth started above 1000 K in the bond-coat layer near the interface with the thermally grown oxide layer, leading to the development of voids over the entire interface due to void coalescence. Such development of voids corresponds to the generation and propagation of thermally grown cracks, i.e., to the initial spallation of the coating.