Mechanisms of crack healing in dense Yb-Si-O environmental barrier coatings by plasma spray-physical vapor deposition

Abstract

Due to high thermal stress level and low strain tolerance, through-thickness cracks are generally observed in plasma-sprayed environmental barrier coatings (EBCs) with dense microstructures, providing shortcuts to water vapor volatilization and molten salt penetration during service in combustion environments of gas turbines. In this study, crack-free and dense Yb-Si-O EBCs were successfully prepared by plasma spray-physical vapor deposition (PS-PVD) and annealing treatment. Closure and healing of through-thickness crack were observed via scanning electron microscopy, while phase transformation and sintering behavior were characterized by X-ray diffraction and nanoindentation. Furthermore, crack healing mechanisms of dense PS-PVD EBCs were elucidated utilizing a microstructure-based finite element model with physically-based constitutive relation. This work provides a foundation for the development of high-performance EBCs and thermal/environmental barrier coating (T/EBC) systems.