Stress distribution around the reaction layer of CMAS and GdPO4 thermal barrier coatings based on finite element analysis

Abstract

GdPO4 thermal barrier coatings (TBCs) have high resistance to calcium‑magnesium-alumina-silicate (CMAS) attack due to the formation of a dense reaction layer mainly consisting of the apatite phase. In this study, stress evolution of CMAS covered GdPO4 TBCs during cooling, and the influence of the reaction layer roughness and thickness on the stress distribution are investigated by the finite element method. During cooling, the tensile stress concentration of σMPS occurred around the peak point of the reaction layer/GdPO4 interface. With the increase of the reaction layer roughness, the ranges of high tensile stress (σ22 and σMPS) and high shear stress (σ12) zones expanded. Increasing the reaction layer thickness also enlarged the high tensile stress (σ22 and σMPS) zone. Due to the high tensile stress and shear stress concentration, the interface between the reaction layer and the GdPO4 coating was easy to crack and separated. Decreasing the reaction layer roughness and thickness was beneficial to reduce the interface stress.