Evaluation of thermal gradient mechanical fatigue characteristics of thermal barrier coating, considering the effects of thermally grown oxide

Abstract

Gas turbines of aircraft and power generation plants operate at a high turbine inlet temperature (TIT) or combustion temperature higher than 1,000°C to obtain high thermal efficiency. The parts directly in contact with the high temperature flame are made of a nickel-base superalloy, which has strong heat resistance. In addition, the thermal barrier coating (TBC) technique is applied to increase the heat resistance. The TBC prevents direct heat transfer from the high temperature flame to the metallic substrate. Thus, the TBC technique reduces the substrate surface temperature by approximately 100~170°C. The delamination caused by the growth of thermally grown oxide (TGO) decreases the life of the TBC system. In addition, gas turbine blades experience centrifugal forces owing to high speeds of approximately 3600 rpm and they experience low cycle fatigue because of frequent startup and shutdown. Therefore, the integrity of the TBC system should be evaluated under the thermal gradient mechanical fatigue condition. In this study, finite element analysis (FEA) was performed for the TBC model considering TGO, and the effect of TGO on TBC systems was evaluated under the thermal gradient mechanical fatigue condition.