Effect of the overlap ratio on surface properties of 7B04 aluminum alloy for aviation during laser derusting

Abstract

Due to the harsh service environment of military aircraft, aluminum alloy on aircraft is prone to corrosion. Maintenance personnel need better rust removal methods to ensure the smooth progress of the flight mission. In this paper, the rust layer on the surface of 7B04 aluminum alloy was cleaned by nanosecond pulsed laser and mechanical grinding. Then the effects on surface morphology, surface roughness, surface hardness, residual stress and corrosion resistance of aluminum alloy were analyzed to determine an improved derusting method and optimize laser cleaning parameter based on the overlap ratio (η). Results showed that mechanical grinding not only did not remove rust completely but also damaged the matrix. When the laser scanning speed was 5650 mm s−1, η was 80%, the rust of the sample was completely removed without damaging the matrix. At the same time, the hardness and corrosion resistance of surface were improved and the appropriate increase of roughness was conducive to the repair of surface coating. When the scanning speed increased and the overlap ratio decreased, there was rust residue which can not meet the requirements of rust removal. When the scanning speed decreased and the overlap ratio increased, the rust was completely removed and the corrosion resistance of the surface was enhanced, but it caused excessive ablation damage to the matrix. And the above two cases will increase the difficulty of coating repair.

Keywords

• Aluminum alloy
• Laser cleaning
• Overlap ratio
• Residual stress
• Scanning Kelvin probe