Magnetic Field Aided Laser Process

Abstract

Conventional laser processes rely on optimizing process parameters to improve product quality and performance, thus to achieve set goals. However, the actual implementation is limited due to many factors such as time-consuming, narrow adjustable window, inter-influence between process parameters, and so on. A novel laser process controlling approach is therefore proposed, which couples a steady magnetic field to the laser system thus to assist the laser melt process, resulting in the improvement of coating surface morphology, The applied steady magnetic field suppresses the undulation of the coating surface by the dissipating effect on the molten pool dynamics. A 2D transient multi-physics numerical model, which concerns heat transfer, fluid dynamics, phase transition and magnetic field, is employed to study the suppression effect of a steady magnetic field on the molten pool during laser remelting. The dynamic shape of the laser remelting surface is explicitly simulated by an Arbitrary Lagrangian-Eulerian method (ALE). The Lorentz force generated by the steady magnetic field, the Marangoni convection formed by surface tension and the thermal buoyancy with Boussinesq approximation are all taken into account in the model. The simulation results are compared with experimental data, showing good agreement. These results demonstrate that the Lorentz force due to a steady magnetic field is a sort of drag force of the melt flow, which significantly reduces the flow velocity. The surface undulation is effectively suppressed by a steady magnetic field so that a smooth surface after laser remelting can be achieved.