Thermographic Quality Assurance of Turbine Engine Components

Although highly desirable from a cost and reliability standpoint, 100% inspection of Ni-super alloy components in the early stages of the manufacturing process has generally been regarded as overly time consuming, and ineffective at identifying subsurface irregularities in the internal structure. As a result, quality assurance is often limited in scope. To rectify the situation, we have implemented a 100% inspection system for quality assurance at Stolper Fabralloy using an active thermography system (EchoTherm, Thermal Wave Imaging, Inc.). Prior to installation, a series of tests were performed to insure that the system could meet customer requirements and match the resolution of the ultrasonic C-scan that had previously been used for QA of flat panels. As a result of these tests a calibration procedure was developed. The system is currently used to inspect flat and formed transition panels and other components using various thermal excitation methods. Operators have been trained per ASNT TC-1A Level I and II. Using the thermographic system, we have successfully identified defects including inter-layer disbonds and cooling channel blockage. The system software allows us to simultaneously view and analyze the results for an entire transition. Total inspection time has been reduced by an order of magnitude, to 30 minutes for a 2’ × 3’ transition.