A study on hydrodynamics of melt expulsion in pulsed Nd: YAG laser drilling of titanium

Abstract

Laser drilling of titanium and its alloys is widely used in aerospace industry, as it offers selective removal of material at high accuracy and speed. However, laser drilling often inherits defects such as large heat affected zone, micro cracks and recast layer. These defects depend upon complex melting and solidification phenomena happening due to interaction of high intensity laser with the material. Therefore, to understand and control these processes, a multi-phase (solid, liquid, and vapor) axisymmetric model is computed using Comsol Multiphysics(R). Moving mesh feature is used to simulate the melt displacement based on the physical processes involved. The model also studies the effect of different laser intensity profiles (ideal gaussian profile (TEM00) and a top-hat profile) on temperature distribution, melt velocity and the shape of the keyhole. The study is useful in optimizing the laser parameters to obtain features with minimum re-solidification, which in turn affect the surface roughness of the ablated region.