Laser cleaning for inorganic thermal control coatings on aluminum alloys: Microstructure evolution and mechanical properties of substrate

Thermal control coatings are crucial materials in spacecraft thermal protection systems. Investigating efficient, convenient, and environmentally friendly removal techniques for thermal control coatings is essential for their application and development. This study developed a new removal technology for thermal control coatings using nanosecond pulse laser cleaning technology. The removal effect of the thermal control coating was studied, and the microstructure evolution and mechanical properties of the substrate were analyzed. The results showed that the coating was completely removed at 5.73 and 7.00 J/cm2, while at 8.28 J/cm2, in addition to the coating, approximately 5±1.1 μm of the substrate was also removed. In the completely cleaned state, micro-melting occurred on the substrate surface, and nanostructures appeared. At 5.73 and 7.00 J/cm2, the thickness of the remelted layer is 4±0.9 μm and 5.5±0.6 μm, respectively. The grains in the remelted layer exhibit significant refinement, accompanied by the observation of numerous subgrain boundaries. Additionally, the substrate surface exhibits tensile residual stress after laser cleaning. Attributed to the influence of the remelted layer, the surface hardness and tensile properties of the substrate are slightly improved after laser cleaning compared to manual grinding.