Experimental study on debonding defects detection in thermal barrier coating structure using infrared lock-in thermographic technique

The infrared lock-in thermographic (LT) technique was used to detect debonding defects in ZrO2 coated Ni-based super alloy GH4169 plates. The basic principle of infrared LT technique and the correlated extraction algorithm of thermal wave signal feature was described. Experiments were performed to investigate the influence of the light source output power, number of analysis periods and modulation frequency on the detection results. Results show that, for the given size range of sample defects, greater total phase contrast CPh can be obtained while the light source output power is 1000 W, number of analysis periods is 4, and modulation frequency is 0.2 Hz, respectively.