Microdamage-coupled inelastic deformation analysis of ceramic thermal barrier coatings subjected to tensile loading

To protect the hot parts of a gas turbine (GT) from high-temperature combustion gas, thermal barrier coatings (TBCs) are deposited on the surface of the blades and the inner surface of the combustor. Thermal stress is cyclically generated in TBC systems by the start-steady-stop operation of the GTs, resulting in TBC spallation. Recently, it has become necessary for electricity generation companies to adopt TBC life assessment technology to determine the appropriate interval to maintain the TBC. Therefore, we decided to develop a numerical code for damage-coupled inelastic deformation analysis of GT components coated with TBCs. In this study, a finite element (FE) code was developed based on the commercial FE software MARC by implementing both the complete deformation model of the inelastic constitutive equation for TBCs, which was developed by us, and the Chaboche-type viscoplastic constitutive equation for nickel-based superalloy IN738LC. The simulation of the damage process, including crack initiation and propagation in TBC systems, was conducted under tensile loading using this FE code. It was shown that the crack propagation feature simulated using the FE code completely matched the continuous observation results obtained in the high-temperature tensile test.