Measurement of thermal barrier coating thickness of turbine blade based on THz-TDS

Chunlian Li; Qiang Niu; Ji Cao; Zhenwei Zhang; Jianchao Li; Lu Wang; Qing He; Yuping Yang; Cunlin Zhang

doi:10.1117/12.2604059

18 October 2021 Measurement of thermal barrier coating thickness of turbine blade based on THz-TDS

Chunlian Li, Qiang Niu, Ji Cao, Zhenwei Zhang, Jianchao Li, Lu Wang, Qing He, Yuping Yang, Cunlin Zhang

Proceedings Volume 11906, Infrared, Millimeter-Wave, and Terahertz Technologies VIII; 119061L (2021) https://doi.org/10.1117/12.2604059
Event: SPIE/COS Photonics Asia, 2021, Nantong, JS, China

Abstract

In this paper, the coating thickness of thermal barrier coating (TBC) on gas turbine blades is measured by terahertz time domain spectroscopy system. At present, the most mature and widely used ceramic layer (TC) material is yttria partially stabilized zirconia (YSZ). In order to measure the coating thickness on TBC surface by terahertz spectrum, it is necessary to determine the optical properties (refractive index and absorption coefficient) of coating material YSZ in terahertz band. The refractive indexes of YSZ samples in terahertz band under different preparation conditions were obtained by transmission THz-TDS. The refractive indexes of these samples were different under the influence of different process parameters and spraying conditions. Then the time domain signal of TBC sample is obtained by reflective THz-TDS, and the coating thickness is obtained according to the time delay of terahertz wave transmission in the sample. When THz wave propagates at different depths of the sample, the dispersion is different, resulting in waveform broadening. We qualitatively analyze the influence of waveform broadening on thickness measurement. The results show that, within the error range, the coating thickness obtained from the time delay between the negative peak of surface reflection signal and the negative peak of interface reflection signal is in good agreement with the thickness measurement results of metallographic method. The optical properties of YSZ material and the thickness of thermal barrier coating are nondestructive tested in THz band.

Citation Download Citation

Chunlian Li, Qiang Niu, Ji Cao, Zhenwei Zhang, Jianchao Li, Lu Wang, Qing He, Yuping Yang, and Cunlin Zhang "Measurement of thermal barrier coating thickness of turbine blade based on THz-TDS", Proc. SPIE 11906, Infrared, Millimeter-Wave, and Terahertz Technologies VIII, 119061L (18 October 2021); https://doi.org/10.1117/12.2604059

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KEYWORDS

Coating

Refractive index

Terahertz radiation

Reflection

Ceramics

Signal attenuation

Absorption

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