A characterization of laser cleaning painting layer from steel surface based on thermodynamic model

In this study, the environmentally friendly nanosecond ultraviolet (UV) laser is an innovatively employed laser cleaning to remove the painting layer from the AH36 steel substrate. The feasibility of UV laser cleaning the painting layer is innovatively proposed and it has been calculated by the model theoretically, followed by elaborating the prominent interaction mechanism of UV laser exactly. The initial cleaning threshold and completely cleaning threshold are 2 J/cm² and 5 J/cm², respectively. Afterwards, the UV laser-cleaned surface quality is evaluated by the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), optical microscopy (OM), and optical profiler (OP), respectively. The mechanical properties have enhanced dramatically after laser cleaning and characterized by the Vickers hardness tester and universal testing machine. By varying laser fluences (2, 5, 7 J/cm²) during laser cleaning, microstructures registering various sizes of corrugated shaped, craters, and ring shaped could be acquired. In addition, the mechanical properties analysis including rapid melting, quenching, and dislocation density effects illustrates that laser cleaning could effectively increase surface microhardness, tensile strength, and bending strength. Thus, laser cleaning method has emerged as a favorable means to strip painting layer in lieu of traditional methods for marine industry as well as this study could promote the development of laser cleaning in the field of marine engineering.