Subsurface damage in laser-assisted machining titanium alloys

Abstract

Laser-assisted machining is an effective to improve the machinability of hard-to-machine material which has been already applied to titanium alloys. To reveal the subsurface damage in laser-assisted machining, the molecular dynamic simulations were performed on a novel titanium polycrystal crystals model, and the effects of scratching velocity and laser power on cutting force, temperature distribution, material removal volume, subsurface damage depth, phase transition, dislocation were investigated and discussed. The results showed that laser assistance can enhance the machinability through cutting force and material removal volume, and reduce subsurface damage. Comparative analysis indicated that subsurface damage was the result of competition between the stress field generated by the cutting force and the laser-induced temperature field, which means excessive laser power will inhibit the improvement of laser assistance. Laser-assisted scratching experiments were also performed under stress field dominated condition on a TC17 material, and prominently reduced subsurface damage was achieved compared to traditional scratching. Multiple kinds of subsurface damage underneath the scratched surface were induced by TEM analysis. This research enhances the understanding of subsurface damage law under different processing parameters and provide a way to obtain optimal subsurface damage depth in laser-assisted machining.