Application of massive laser shock processing for improvement of mechanical and tribological properties

The present paper aims to investigate topographical, microstructural, mechanical and tribological behaviour of precipitation hardened Al alloy subjected to massive laser shock processing (LSP) without protective coating at 2500 pulses/cm(2), using three beam diameters. Wear tests under dry sliding conditions resulted in severe wear, whereas the main wear mechanisms were adhesion accompanied by abrasive wear. Nevertheless, LSP with optimal processing parameters reduce the friction coefficient and wear rate with lower degrees of adhesion and abrasion inside the wear track in comparison to the untreated sample. The enhanced tribological performance is attributed to the positive influence of LSP induced surface topography, surface compressive residual stresses (RS) and dense dislocation arrangements, as the result of high-pressure shock waves. Nonetheless, due to the narrow window of optimal parameters reduced wear resistance as a consequence of undesired thermal/softening effect due to laser ablation and melting was detected with non-optimal processing parameters.