Stress evolution during three-dimensional dynamic growth of thermal barrier coatings under isothermal cyclic field

Thermal barrier coatings (TBCs) are essential for thermal insulation and oxidation protection in turbine engines, yet their failure due to micro-cracking and spallation remains a critical challenge. This failure is primarily driven by complex internal stresses arising from thermal expansion mismatch, dynamic growth of the thermally grown oxide (TGO) layer, and inherent microstructural defects. While prior research has offered insight, prevailing two-dimensional models often overlook the dynamic nature of TGO evolution and the three-dimensional complexity of pore networks, limiting a holistic understanding of stress mechanisms. Here, we have developed a three-dimensional finite element model to investigate stress evolution under isothermal cycling, incorporating dynamic TGO growth, material creep, diverse 3D pore morphologies, and pore-interface roughness interactions. Results show that TGO growth progressively elevates interfacial stresses, while creep provides critical relaxation. The presence of pores significantly amplifies stress magnitudes, with morphology and orientation critically influencing local concentrations. Furthermore, a strong non-linear coupling exists between interface roughness and pores, where their combined effect peaks at a specific roughness ratio. These findings elucidate the complex, multi-factor failure mechanisms in TBCs and provide guidelines for designing more durable coating systems.