Study on removal of aluminum alloy oxide film by continuous-nanosecond combined laser with different pulse delays

In this paper, the thermal stresses arising from thermal expansion and the adsorption forces between the oxide film and the substrate are calculated from the one-dimensional heat conduction equation. Comparing the magnitude of the two, the laser cleaning conditions are obtained, and relevant models such as plasma shock wave pressure are established. The plasma plume, surface morphology, and elemental composition of aluminium alloy oxide film removed by continuous-nanosecond combined laser with different nanosecond pulse delays were experimentally investigated. At total laser fluence of 3630.47 J/cm2 (continuous laser fluence of 3628.73 J/cm2 and nanosecond laser fluence of 1.74 J/cm2), the removal effect is better with the increase of pulse delay, and the best removal effect is achieved when the pulse delay is 600 ms. Based on the experimental results, the mechanism of oxide film removal by combined lasers with different pulse delays was discussed, and at least two mechanisms of thermal stress against adsorption and plasma shock wave breaking the oxide layer were present to act.