Thickness measurement of thermal barrier coating using varactor tuned resonant probe

Thermal barrier coatings (TBCs) are critical in aerospace and energy applications for protecting components from extreme temperatures. Accurate and reliable evaluation of TBC thickness is essential for ensuring the structural integrity and performance of coated components. This study introduces an innovative method for TBC thickness evaluation using a varactor-tuned resonant probe. By leveraging the probe's tunable resonant frequency and a portable reflectometer, the system offers precise single-frequency measurements without the need for bulky vector network analyzers or frequency sweeping. This innovation addresses a key limitation of previous microwave TBC thickness measurement methods, significantly enhancing their practicality and efficiency. The proposed approach demonstrates enhanced accuracy, ease of use, and potential for in-situ evaluations compared to existing non-destructive testing (NDT) methods. Experimental results validate the system's ability to achieve high accuracy in TBC thickness estimation, achieving a 95 % confidence interval of ±22.4 μm (2σ) for TBC thickness range of 100–550 μm.