Underwater Coaxial Laser-Waterjet Micromachining of Titanium

Thermal damage is a crucial issue in laser micromachining process, so liquid-assisted laser ablation techniques have been developed to overcome this challenge. This study presents the underwater coaxial laser-waterjet micromachining process, which combines the advantages of the waterjet-assisted laser and underwater laser ablation techniques. Titanium was selected as a work sample in this study, where the effects of waterjet flow rate and laser traverse speed on groove width, groove depth, and heat-affected zone (HAZ) were investigated. The influences of the flow rate on the flushing of cut particles and laser beam scattering were also examined to determine the critical flow rate for minimizing the laser beam interference in water. The waterjet flow rate of 250 mL/min was found to be an optimum level, at which a deep groove with a minimum HAZ and clean ablated surface was achievable by the proposed process. Using the flow rate greater than this level in turn caused more laser beam scattering due to the formation of cavitation bubbles and then resulted in the decreased groove dimensions. According to the findings of this study, the proposed coaxial laser-waterjet ablation technique can be another promising process for precisely and damage-free cutting heat-sensitive materials in manufacturing.