Investigation on Topcoat Uniformity of Thermal Barrier Coating Using Pulsed Infrared Thermography

In this study, the uniformity of the topcoat of a thermal barrier coating (TBC) was investigated using pulsed infrared thermography. Two plasma-sprayed TBC samples on different substrate materials, with non-uniform topcoats varying from 0.1 mm to 0.6 ㎜ were considered. A short high-energy light pulse was applied to the surface of the samples, and an infrared camera was used to record surface temperature evolution during the entire thermal transient period. The relationship between the measured temperatures and their spatial distributions in the non-uniform topcoat was studied, and it was observed that temperatures in the thinner topcoat region were lower than those in the thicker topcoat region. Furthermore, the recorded thermal image sequences were processed using Fourier transforms to obtain phase angle images, and the phase angle distribution was examined as a function of the non-uniform topcoat. It was found that phase angle decreased with topcoat thickness. Our results showed that variations in temperature and phase angle were significantly correlated with non-uniformity in our investigation of TBC topcoat uniformity.