Evaluation of Applicability of Compact Excitation Light Source to Detection of Thermally Grown Oxide Layer in Thermal Barrier Coating for Gas Turbines

A compact, continuous wave laser was applied to detection of the thermally grown oxide (TGO) layer in a thermal barrier coating (TBC) for gas turbine high-temperature components by photoluminescence. Experiments were conducted using TBC specimens heated in air to artificially produce a TGO layer. For specimens heated at 1100 degrees C, the photoluminescence intensity increased with heating time, whereas for specimens heated at 1000 degrees C, the photoluminescence intensity did not increase beyond 100 h. The results indicate that the formation of the TGO layer is strongly dependent on the temperature. In addition, scanning electron microscope (SEM) observations of the specimen cross section confirmed the formation of the TGO layer after heating for 100h at 1100 degrees C. The applicability of a compact laser to TGO layer detection allows the development of a simple TGO detection system, which can be used in screening for the detailed inspection of delamination.