Stress Optimization of TBC System Based on Parametric Study of Aluminum Depletion and TGO Growth

Thermal Barrier Coating (TBC) system has been increasingly applied to gas turbine engine because of its outstanding ability to effectively protect substrate materials against impinging hot gas. However, the durability issue has still existed due to the growth of oxidation layer called thermal growth oxidation (TGO) and depletion of aluminum. Therefore, more detailed investigation is required to understand the effects of these two factors on the durability of TBC. In this study, a finite element (FE) model was developed to calculate the stress state near TGO interfaces by considering both the morphology of TGO and aluminum depletion effect. For acquiring the mechanical properties at the depletion area of bond coating layer, indentation tests were carried out, particularly, to the TBC specimens isothermally exposed at 1000 degree Celsius for 100h. Based on the proposed FE model with specific parameters obtained from experiments, parametric studies were performed in a variety of conditions of mechanical properties and TGO thickness. Simulation results clearly showed the influence of aluminum depletion and TGO growth on the durability of TBC system. Finally, optimal design criteria can be suggested to minimize the stress of TBC system.