Thermal barrier coatings prepared by suspension plasma spraying have strain-tolerant structures, e.g. vertical crack and columnar structures, which have been proven beneficial to thermal shock performance. During extended thermal exposure, sintering-induced densification and stiffening behaviors need to be considered for the failure analysis. In this work, the fracture mechanisms induced by thermal shock and sintering are elucidated, shedding light on the multi-crack competition between branching cracks and interfacial cracks. Coating samples were prepared by suspension plasma spraying with a self-developed feeding system. Thermal shock behaviors were characterized via both water quenching and burner-rig tests. Temperature-dependent sintering models, as well as finite element algorithms for multi-crack competition, were further developed. Mechanisms of sintering-induced evolution and multi-crack failure under thermal gradient were analyzed. Results showed that interface strength was the controlling factor of multi-crack fracture mode, while accelerated sintering was responsible for the propagation of horizontal branching cracks near the surface.
 

Thermal Barrier Coatings,Suspension Plasma Spray,Thermal Shock,Sintering,Failure Analysis