Experimental analysis of Nd3+:YAG laser-assisted ablation on piston ring surface in an environmentally friendly underwater ambiance

Abstract

The present work focuses on the nanosecond pulsed Nd3+:YAG laser-assisted ablation on the chromium-coated piston ring surface. The influence of laser pulse energies and the number of laser pulses on dimple size at different ambient conditions such as air, underwater (still condition) and underwater (flowing condition) is studied. An underwater laser ablation setup was developed especially to perform underwater laser machining (surface texturing) aimed at avoiding the metallic vapor pollution formed when the laser beam irradiates the target surface. The dimple diameter was maximum with underwater (still condition) followed by air and underwater (flowing condition) for all the corresponding laser pulse energies. The dimple depth was maximum with air ambiance followed by flowing underwater ambiance and still underwater ambiance for all the corresponding laser pulse energies. In underwater ambiances, the re-deposition layer around the dimple was lesser. A part of the melt pool formed in underwater ambiance (still condition) might be dissolved in water. The remaining melt pool is distributed around the dimple as a thin layer. In the case of the underwater flowing ambient condition, flowing water distributes the re-deposition layer further away compared to the underwater still ambiance. The re-deposition layer was substantially minimized around the dimple in both the underwater laser ablation conditions. An increase in compressive residual stress is observed around the dimple formed in underwater laser ablation both in still and flowing conditions. Though the underwater laser ablation (flowing) is more complex, it is found to be more beneficial compared to ablation in air ambiance.