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- Title
Nondestructive Thickness Measurement of Thermal Barrier Coatings for Turbine Blades by Terahertz Time Domain Spectroscopy.
- Authors
Liu, Longhai; Yu, Haiyuan; Zheng, Chenglong; Ye, Dongdong; He, Wei; Wang, Silei; Li, Jining; Wu, Liang; Zhang, Yating; Xie, Jianhua; Yao, Jianquan
- Abstract
Owing to its high penetrability with dielectric materials, terahertz time domain spectroscopy (THz-TDS) is a promising nondestructive measurement technology. The coating thickness deviation and defect of thermal barrier coatings (TBC) will affect its thermal insulation performance and lifetime. In this work, THz-TDS was applied to measure the coating thickness distribution of TBC. The refractive index was obtained by THz-TDS transmission mode. To avoid the normal incidence THz signal loss, the THz signal was reflected from the TBC with a 10° incident angle, which also made the measurement result insensitive to the unevenness and tilt of the TBC sample. In the experiment, the yttria-stabilized zirconia (YSZ) TBC was measured by THz-TDS to estimate the thickness distribution. To validate the thickness measurements, metallography was introduced to correlate the TBC thickness result. The measurement deviation was within 12.1 µm, i.e., 3.45% for the THz-TDS and metallography result. A piece of turbine blade was measured by THz-TDS and a eddy current test. The maximum deviation was 8.48 µm, i.e., 2.36% of these two methods. Unlike the eddy current test, the THz-TDS thickness result was not affected by the cooling holes. The effectiveness of the nondestructive thickness measurement of TBC for turbine blades by THz-TDS was verified.
- Subjects
THERMAL barrier coatings; THICKNESS measurement; TURBINE blades; TERAHERTZ spectroscopy; EDDY current testing; DIELECTRIC materials
- Publication
Photonics, 2023, Vol 10, Issue 2, p105
- ISSN
2304-6732
- Publication type
Article
- DOI
10.3390/photonics10020105