A Numerical study on laser micromachining of titanium alloy using nanosecond pulsed laser

Development of microfeatures using laser micromachining is gaining in popularity in the automobile, aerospace, medical, and electronics industries due to the miniaturization of components. Developing microfeatures such as cooling microholes and surface-enhancing micro dimples on titanium alloys using a nanosecond pulsed laser is challenging due to the risk of thermal and metallurgical defects, including recast layer formation, heat-affected zones, and microcracks. Despite these challenges, nanosecond pulsed lasers are still preferred over picosecond and femtosecond lasers because of their high productivity, reliability, and cost-effectiveness. Micromachining using a nanosecond pulsed laser involves intricate mechanisms, including melting, vaporization, and melt ejection and various forces, such as gravity, viscous, and thermocapillary effects. Therefore, understanding the mechanism through a numerical process is essential, since it is challenging to analyze through experimental processes due to high costs and time constraints. In this work, a non-linear transient finite element-based study of micromachining on titanium alloy using a nanosecond pulsed laser was developed in consideration of these mechanisms and forces. The model incorporates heat transfer, fluid phenomena, and deformed mesh, considering temperature-dependent material properties (including thermal conductivity and specific heat). The developed model studies the dynamic temperature field, velocity field, and morphology evolution behavior. Through the developed model, the maximum predicted ablation depth of around 8 µm at a laser fluence of 50 J/cm 2 and 100 ns pulse duration was observed.