Quantitative evaluation of adhesion quality of surface coating by using pulse laser-induced ultrasonic waves

This study aims to evaluate delamination characteristics of surface coating by using strong ultrasonic wave induced by pulsed laser irradiation. Strong tensile stress wave is induced by pulse laser irradiation, and delamination of the coating layer/substrate interface (or spallation) is produced by confined silicone grease breakdown (i.e. ablation). Upon various levels of energy of irradiation laser, the coating delamination and displacement are measured in-situ. Parallel computation of elastic wave propagation using FDTD (finite difference time domain) yields the wave propagation in the specimen, and estimates the interfacial strength with stress wave distribution. The delamination area is visualized by laser ultrasonic wave scanning technique after the laser spallation test. The interaction between displacement waveform and delamination is explored. The present technique may shed some light on various coating depositions for assessing the coating adhesion quality.