The combined effects of material creep and mechanical loads on the extension of thermally grown oxide instability

Abstract

The instability of the thermally grown oxide is the fundamental source leading to failure relevant to spallation and delamination of top coat. A finite element model is developed to understand failure mechanism of thermal barrier coating systems. Lateral and normal growth strains are stimulated by ABAQUS field variable expansion. Our results show that the valley region of top coat/thermally grown oxide interface and the peak region of thermally grown oxide/bond coat interface are the initiation locations of cracks. The creep can suppress downward displacement at the valley and promote the upward displacement at the periphery. Large material creep induced by further enhanced residual stress can restrain the increasing trend of the tensile stress within top coat and contribute to changes of thermally grown oxide morphology. Conversely, the applied load can promote the downward displacement at the valley and suppress the upward displacement at the periphery. The larger mechanical loads enhance the displacement rate toward bond coat layer, implying that the larger extension rate of thermally grown oxide instability accelerates the coating failure.