Effects of electromagnetic compound field on the escape behavior of pores in molten pool during laser cladding

In order to improve the escape ability of the pores in the laser cladding molten pool, an electromagnetic compound field (ECF) is coupled in the laser cladding system to generate the directional Lorentz force in the molten pool. Based on the multi-physical field coupling theory, a laser cladding molten pool model is proposed, considering the heat transfer, fluid flow, morphology, buoyancy, surface tension, Lorentz force and pore movement of the molten pool. The simulation results reveal that the fluid flow status and geometry of the molten pool are changed significantly due to addition of the directional Lorentz force. The pore escape velocity in the molten pool can be improved effectively with the downward Lorentz force generated by a current of 500 A and a steady magnetic flux density of 1.2 T. On the contrary, more pores are trapped inside the molten pool when the direction of Lorentz force is changed to upward. The experimental observations and data confirm the model results that with the electromagnetic compound field applied, and the escape state of pores in laser cladding molten pool can be effectively controlled. Attributed to the downward Lorentz force, dense cladding layers with low porosity can be achieved successfully.