Nondestructive Thickness Measurement of Thermal Barrier Coatings for Turbine Blades by Terahertz Time Domain Spectroscopy

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 insulation performance lifetime. In this work, THz-TDS was applied measure the distribution TBC. refractive index obtained by transmission mode. To avoid normal incidence THz signal loss, reflected from TBC 10° incident angle, which also made result insensitive unevenness tilt sample. experiment, yttria-stabilized zirconia (YSZ) measured estimate distribution. validate measurements, metallography introduced correlate result. within 12.1 µm, i.e., 3.45% for A piece turbine blade eddy current test. maximum 8.48 2.36% these two methods. Unlike test, not affected cooling holes. effectiveness blades verified.