Numerical Analysis of stress evolution in thermal barrier coating system during two-stage growth of heterogeneous oxide

The mechanical stability of the thermal barrier coating (TBC) systems is important for the heavy-duty gas turbine during operation and maintenance. The growth of thermally grown oxide (TGO), which controls the mechanical stability of TBC systems, usually consists of two stages. In the first stage, the outer mixed oxide (MO) and alumina grow simultaneously. In the second stage, the intact alumina protective layer is gradually replaced by the porous inner MO. The MO deteriorates the interface integrity and exhibits a higher growth rate, which should be investigated. In this study, a numerical method was developed to simulate the stress evolution of two-stage TGO growth. The results show that the inner MO growth can significantly change the stress evolution during high-temperature oxidation and induce higher thermal mismatch stress after cooling down. This adverse effect enhances the risk of TC failure and should be taken seriously in the heavy-duty gas turbine's operation and maintenance.