Experimental study of inspection on SiC coated high-temperature alloy plates with defects using pulsed thermographic technique

The pulsed thermographic technique was used to detect flat-bottomed hole defects in SiC coated high-temperature alloy plates. Temperature–time Logarithm Fitting Method (TtLFM), Principal Component Analysis (PCA) and Pulsed Phase Thermography (PPT) were used to extract the characteristic information of the thermal wave signal generated by thermal pulse. It is found that PCA algorithm is available for analyzing the thermal wave signal generated by thermal pulse due to higher signal–noise ratio. Experiments were performed to investigate the effect on the thermal contrast by the pulse intensity, frame rate and analysis moment, respectively. Experimental results show that larger pulse intensity and frame rate are benefit to get larger thermal contrast thermogram, and optimal analysis moment selected is helpful to detect the defects of SiC coated high-temperature alloy plates using pulsed thermographic technique.

► Three algorithms are used to process the thermal wave signals.
► Detectable probability is affected by the excitation and analysis parameters.
► PCA algorithm can get better detection results in pulsed thermography.