Effects of pulse energy and contact foil thickness on the surface integrity of LY2 aluminum alloy subjected to laser shock wave planishing technology

Abstract

Reducing the surface roughness is an effective way to improve the fatigue performance of aero-engine blades. In this paper, the milled surface of LY2 aluminum alloy was processed by a laser shock wave planishing (LSWP) technology, and the influence of the laser pulse energy and the contact foil thickness on the surface integrity were studied. The results showed that the thinner the contact foil and the higher the pulse energy were, the higher the removal rate of tool marks (the degree to which the milled topography of LY2 aluminum alloy surface is flattened) was. On the contrary, the thicker the contact foil and the lower the pulse energy were, the lower the removal rate of tool marks was. It will cause ‘center depression’ under LSWP with a thin contact foil and a high laser pulse energy, resulting in an increase of surface roughness, a large difference in residual stress and micro-hardness between the center and the laser spot edge. In the overlapping LSWP experiment, when the contact foil thickness matched the appropriate laser pulse energy, the milled surface was flattened without boundary effect, and in 67% overlapping experiment, a thicker contact foil can be used to achieve the same high-quality surface as in 50% overlapping experiment.