Study on damage evolution of TBC by rapid thermal cycling test based on a laser irradiation

Abstract

Thermal barrier coating (TBC) is deposited onto the surface of gas turbine blade in order to prevent from a high-temperature combustion gas flow. Crack and delamination of ceramic coating, which come from a high heat flux loading, are serious problem in TBC. In this study, the rapid thermal cycling device based on a laser irradiation was developed. It was then investigated how the damage progresses in ceramic coating subjected to rapid thermal cyclic loading based on the monitoring of acoustic emission (AE). As a result, a sintered layer was formed in the surface of the ceramic coating, although such phenomenon was not recognized in TBC sample which was tested by a typical thermal cycling test using an electric furnace. It was also found that both vertical and horizontal cracks were initiated and propagated in ceramic coating. The monitoring of AE revealed that most these cracks are initiated in cooling periods at early stage of thermal cycles.