Development of Adhesion Durability Evaluation of Surface Coatings Using Repeated Laser Shock-wave Adhesion Test

This study aims to evaluate coating adhesion durability using the laser shock-wave adhesion test (LaSAT). In particular, the interfacial strength with respect to the applied loading cycle is evaluated quantitatively. This method uses strong elastic waves induced by pulsed laser irradiation, as interfacial fracture of the coating occurs due to a strong wave. The coating delamination can be identified from changes in the out-of-plane displacement waveform, yielding a critical laser energy for coating delamination. Subsequently, computation of elastic wave propagation using the finite difference time domain (FDTD) method was carried out to estimate the tensile stress developed at the coating/substrate interface, yielding the interfacial strength. In addition, the durability of interfacial adhesion was investigated by repeated LaSATs. Repetitive lower stress loading was applied to the interface using repeated laser irradiations. It was found that repetitive loading encourages interfacial fracture, which has a stress level lower than that of single (monotonic) laser irradiation. For various levels of irradiation laser energy, the interfacial adhesion durability was investigated. This result may be useful for evaluating adhesion durability when a coating/film is used under cyclic loading over a long-time duration.