Abstract
A non-destructive method for evaluating the heat resistance of a TBC has been developed for gas turbine blades. In this method, a robot arm controls the position of CO_2 laser beam along the topcoat surface. The laser beam heats the topcoat surface in the vertical direction while maintaining the laser source at a fixed distance from the surface, and the topcoat surface temperature is measured by an infrared camera. Subsequently, to derive an expression for the relationship between the heat resistance and the topcoat surface temperature, three-dimensional analysis of the unsteady heat conduction is performed under practical heating condition. This measured temperature and this relational expression estimate the heat resistance. This method was applied to the cylindrical TBC sample which simulates curvature of gas turbine blade and the heat resistance of the TBC was evaluated under various conditions. The suitable heating condition for this method was decided by these test results. In addition, the results showed that if the measurement error of the topcoat thickness is reduced, the accuracy of this method will be improved.
