Overflow-assisted laser machining of titanium alloy: surface characteristics and temperature field modeling

Abstract

Underwater laser machining process is a promising method to cut materials with less thermal damage. A variation of underwater technique is overflow-assisted laser ablation. This process can introduce a higher thermal convection and more uniform water layer than the typical underwater method. Such characteristics can encourage the damage-free fabrication and also stabilize the laser ablation in water. In this study, cut profile and temperature distribution of workpiece induced by the overflow technique were investigated. Titanium alloy (Ti-6Al-4V) used as a work sample was grooved by a nanosecond pulse laser under different overflow conditions. The effects of laser power, laser repetition rate, and water flow velocity were experimentally and numerically examined. A clean and smooth cut surface can be fabricated when the overflow technique was used. Microcracks and porosities found on the laser-ablated area were also addressed in this study. The temperature field of titanium alloy under the different ablation conditions was simulated by using the finite difference computation. The transient heat conduction model was implemented together with the enthalpy method and temperature-dependent material properties. By using the developed model, the groove depths obtained from the experiment and simulation were in a good agreement.