Nondestructive inspection of gas turbine blades by active thermography using different fluids

Abstract

Presence of defects in the gas turbine blades’ affects the blade performance and reduces the blade life. One of the common defects in the internal cooling passages of a gas turbine blade, is residual ceramic created in the blade production stage. This types of defects, can be beneficially detected by using active thermography. In this paper, nondestructive testing of internal cooling passages of a gas turbine blade is conducted by active thermography method using different types of excitations. Carbon dioxide (CO2), hot air, and water-vapor were selected as excitation sources. Inspection with water-vapor stimulations were performed at three different pressures flow rates. Results indicated that the IR thermography tests with water-vapor excitation, provide higher detectability compared to the other methods. However, internal passages were revealed by all of the pre-mentioned excitation methods. Residual ceramic in internal passages of the blade were clearly revealed by application of hot air and water-vapor. Results also indicated that application of the maximum pressure and flow rate, offer a better detectability and visibility. Some surface defects on the gas turbine blades were also been detected by application of water-vapor excitation.