Research on the enhancement mechanism of subsonic gas flow field in cleaning the paint layer by combining laser-induced plasma shock

Abstract This study proposes a novel method utilizing subsonic flow fields to enhance combined laser-induced plasma shockwaves, achieving non-destructive and highly efficient removal of composite paint layers from 7075 aluminum alloy surfaces. A two-dimensional numerical model was established to systematically investigate the influence mechanisms of gas flow velocity and lateral blowing angle on plasma shockwave characteristics within subsonic flow fields. Time-resolved projection techniques were employed to observe plasma dynamic behaviors, complemented by multi-dimensional characterization of cleaning effectiveness through laser-induced breakdown spectroscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy (EDS). Results reveal that the ‘suppression’ effect and cooling mechanism exerted by subsonic gas flow on plasma clouds constitute critical factors regulating shockwave propagation. When optimized parameters of 0.6 Ma gas flow velocity with 60° incidence angle were applied, significant attenuation of plasma shielding effects and enhanced mechanical action of shockwaves on paint layers were achieved, resulting in improved paint removal efficiency. Surface analysis confirmed that this methodology effectively reduces oxide residues on substrate surfaces while significantly increasing metallic element content, providing a new technical solution for surface treatment of aluminum alloy components in aerospace and related fields.