Terahertz Detection and Evaluation of Thermal Barrier Coating Thickness

Abstract

Thermal barrier coatings are mainly used for thermal protection of turbine blades, and accurate non-destructive measurement of their thickness is a key factor in evaluating the integrity of blade quality. This article uses a reflective terahertz time-domain spectroscopy system to measure the thickness of thermal barrier coating samples, obtaining the refractive index of several thermal barrier ceramic coating material samples under different preparation conditions in the terahertz frequency band. Then, the reflective terahertz measurement system is used to obtain the time-domain signals of thermal barrier ceramic coating samples under different preparation conditions, extract different time-domain features, calculate the coating thickness, and compare them. The phenomenon of waveform broadening caused by dispersion during the transmission of terahertz waves in different samples was studied, and the impact of waveform broadening on the measurement of thermal barrier coating thickness was qualitatively analyzed. Compared with the results of metallographic thickness measurement, the deviation of the results is within the error range, and the comparison results show good consistency. It also provides useful reference for using terahertz technology to detect the thickness of thermal barrier coatings on turbine blades and evaluate structural quality.