L. Y. Lim, Tongyu Wu, S. A. Meguid
In this paper, the transient thermomechanical response of bilayered GDZ/YSZ thermal barrier coating (TBC) and the role of interphase regions in this multilayer system are investigated. A coupled transient finite volume–finite element (FV–FE) framework is employed to model the thermomechanical response of both single-layer (GDZ, YSZ) and bilayered GDZ/YSZ coatings, accounting for thermal cycling, bond coat oxidation, and temperature-dependent material properties. The effects of coating configuration and material properties on the evolution of residual stresses are systematically examined. In addition, molecular dynamics (MD) simulations are utilized to characterize the thermomechanical properties of interphase regions, particularly at the GDZ/YSZ interface. The results reveal that larger direct stresses, [Formula: see text], develop in single-layer GDZ coatings compared to YSZ due to the greater thermal mismatch with the substrate. In both GDZ and bilayered GDZ/YSZ topcoats, the location of peak residual stresses shifts from the peak to the valley of the surface undulation during thermal cycling. Furthermore, the stresses within the GDZ layer of the bilayered system show limited variation with thermal cycling, indicating a shielding effect provided by the underlying YSZ layer. Insights from MD simulations suggest that the GDZ/YSZ interphase exhibits reduced stiffness and thermal conductivity relative to the bulk materials, which may contribute to local compliance and influence stress redistribution within the coating system.