Effective laser cleaning of radar absorbing coatings on roughened aluminum alloys: surface integrity and overall performance

Radar absorbing coatings are prone to damage in harsh operating environments, requiring prompt removal and repair to maintain their functionality. In this study, radar absorbing coatings on roughened aluminum alloy surfaces were successfully cleaned using a UV picosecond laser, with the influence of different energy densities on surface integrity and overall performance systematically analyzed. The optimal laser cleaning energy density is determined to be 2.41 J/cm², enabling complete removal of radar absorbing coatings while maximally preserving original substrate morphology and minimizing oxidation. At 3.03 J/cm², spherical microstructures form on the surface, evolving into cluster protrusions at 3.66 J/cm². Only a 5 nm amorphous oxide layer forms on the surface after laser cleaning at 2.41 J/cm². When the laser energy density increases to 3.66 J/cm², this layer thickens to 8 nm with spherical oxide particles in the near-surface region, while the overall cross-sectional microstructure remains unchanged. These changes in morphology, composition, and microstructure significantly influence surface performance. While higher energy density improves hardness and wear resistance, excessive energy density leads to a decline in corrosion resistance. Particularly, UV picosecond laser cleaning only modifies the near-surface layer of the substrate, leaving the internal phase composition, microstructure and bulk mechanical property virtually unaffected.