Design and Optimization of Interface Morphology of Thermal Barrier Coatings Based on Regulation of Residual Stress: A Finite Element Simulation Study

Abstract

Laser surface texture (LST) technology can be used to increase the adherence of thermal barrier coating (TBC). The primary research method is to conduct a large number of laser experiments to determine the optimal texture parameters. To minimize costs and enhance efficiency, in the current work, five types of circular pit textures were summarized; the plane strain model was established using the transient thermomechanical coupling finite element method; the residual stress field after spraying was used as the prestress field; the influence of different textures on the distribution of the residual stress field after a thermal cycling was analyzed; and the propagation law of cracks in the coating was predicted. The current work focuses on: (1) The two-dimensional cross-sectional morphology of texture; (2) the principal stress s22 perpendicular to the interface (resulting in mode I interface crack) and the shear stress s12 parallel to the interface (resulting in mode II interface crack); (3) texture variables—diameter, depth, and spacing. The results revealed that after thermal cycling, the texture in the ceramic top coat (TC) bore tensile stress of around 350 MPa. Both sides of the pit in the metallic bond coat (BC) bore tensile stress, while the bottom bore compressive stress. Among them, the positive tensile stress of the texture with a sinusoidal section was the greatest, whereas the shear stress was the least. The maximum stress in texture increased as the diameter and depth increased, while the minimum principal stress was obtained by adjusting the spacing among the adjacent textures. The stress level in the coating was reduced by selecting the appropriate texture morphology, and the crack propagation was more complex, that is, it took a longer time before reaching failure, which is expected to improve the life.