Laser-induced removal of thermal control coatings on aluminum alloy surfaces: Thermal-impact coupling effects and processes

Currently, the practicability of laser-induced cleaning of thermal control coatings (TCCs) has been preliminarily verified. To expedite practical applications, this study evaluated the laser cleaning effects of TCCs and the cleaned surface condition from the perspective of laser scanning speed. The findings revealed that laser ablation served as the dominant cleaning mechanism, with plasma impact playing an auxiliary role. Interestingly, trace coating residues may remain during the cleaning process. These residuals are primarily attributed to the redeposition of splattered coating particles generated by impact and the accumulation of thermal decomposition products of the coating. Additionally, the laser coating removal process can lead to surface melting of the substrate. Due to the rapid cooling of the molten materials and the combined thermal and impact effects caused by laser irradiation, the grain size within the resolidified zone was significantly refined, and numerous subgrain boundaries were observed. Meanwhile, significant orientation deviations between grains were observed near the substrate surface. Notably, some Al inevitably evaporated during the laser-induced removal process, and the redeposition of the evaporated Al formed an oxide layer with micro-nanostructures on the substrate surface.