A Comparison between Nondestructive testing of gas turbine blades by active IR Thermography using optical and water-vapor excitations

In this research, the application of active thermography in the nondestructive testing of gas turbine blades was investigated. Optical pulsed excitations with various excitation times were applied to the two similar gas turbine blades with defects in different sizes. The thermal images obtained by this type of excitation indicated that the pulsed optical thermography can detect the surface cracks, however the internal defects such as residual-ceramic remains undetectable. Moreover, lower scale cracks are also barely detectable. The resultant thermal images are compared with the outcomes of water-vapor excitations. In contrast to optical excitation the water-vapor excitation shows excellent capability in detection of internal defects. All the cooling passages are identifiable and residual-ceramic defect can be obviously detected.

Keywords:

Gas Turbine Blade , Nondestructive Testing , IR Thermography , Optical Excitation , Water-Vapor Excitation