Investigations on enhancing the surface mechanical and tribological properties of A356 Al alloy using pulsed laser-assisted nitriding

Abstract

This paper demonstrates the influence of pulsed laser-assisted nitriding (in an open atmosphere with N2 gas purging) and pulsed laser processing (without N2 gas purging) of A356 Al alloy on the surface mechanical and fretting wear properties. The influence of laser fluence in the range of (50–450 J/cm2) on the thickness of the nitride layer, surface quality (discolored concentration % and roughness), nanomechanical and fretting wear behavior was investigated in detail. The pulsed laser-assisted nitriding has yielded the typical gold-colored AlN compound layer at the laser fluence of 100 J/cm2. Exceeding the fluence limit has caused microvoid and oxide layer formation and eventually reduced the thickness and hardness of the nitride layer. In case of pulsed laser processing, the optimized fluence was found to be 200 J/cm2. The pulsed laser-assisted nitriding and processing have improved the hardness up to 44.8% and 16.3% respectively in comparison to the untreated specimen (1.49 GPa). Whereas the fretting wear volume was reduced by five and two times for the pulsed laser-assisted nitriding and processed specimens respectively.