Eddy current testing for internal cracks around air film aperture of turbine blades

Cooling film hole is an important thermal protection method for advanced aero-engine turbine blades. During the processing and service of film holes, minor crack defects may occur around the holes. To ensure the safety and integrity of turbine blades and aero-engines, nondestructive testing needs to be conducted. To address the issue of detecting crack defects on the inner walls around turbine blade film holes, an import-type eddy current probe configuration was proposed, which could import the eddy current field into the deeper hole interior; through simulation analysis and experimental research, the effectiveness and feasibility of this probe configuration were verified. To address the interference and impact of narrow inclined hole structures on eddy current testing, an eddy current testing method based on the differential principle was proposed, and an eddy current testing probe specifically for inclined film holes was designed and manufactured. Experimental results showed that the amplitude information of the eddy current testing signal reflected the size of cracks inside the inclined holes, and it had good detection effectiveness for internal cracks around inclined film holes of turbine blades.