Modelling on How Topcoat/Bond Coat Micro-Rough Interface and Nearby Voids Affect the Stress Distribution in Thermal Barrier Coating Systems in Quenching Process

The distribution of voids in ceramic topcoats (TC) and the micro-roughness of metallic bond coat (BC) interfaces are important for the structure design and coating life of thermal barrier coating (TBC) systems. In this study, finite elemental (FE) models were built by considering those two structural factors to investigate their influence on the stress distribution in TBCs in quenching processes under thermal shock conditions. According to the simulation analyses, the function of the voids in TCs includes the dilution effect of the stress concentration at the macro-scale, the releasing effect of the tensile stress along the vertical direction above the TC peak, and the “stress trapping” effect bringing higher stress at the horizontal tips of the voids on the micro-scale. The micro-roughness of the TC/BC interface did not have much effect on the stress values in the TC, aside from at the TC peak, but had a significant influence on the stress value along the interface due to the “stress trapping” effect. The TBC samples that were experimentally tested under water-cooling thermal shock conditions were also analyzed in this paper to verify the modelling results.