Evaluation of Spatial Resolution of Nondestructive Testing of Thermal Barrier Coating by Terahertz Imaging

Abstract

The spatial resolution of THz imaging in nondestructive testing of thermal barrier coating was evaluated. The instrumental resolution was evaluated using a test pattern and was found to be about 0.6mm. The test pattern under a YSZ sample of thickness 1.25mm could be identified from the spatial distribution of the wave reflected from the back side of the YSZ sample, with a planar spatial resolution of about 1mm. THz imaging successfully detected an artificial defect of 1mm×1mm under the topcoat in a TBC sample. The results showed the possibility of detection of surface defects under the topcoat by THz imaging.