Study on molten pool dynamics and hump formation mechanism in laser wire feeding additive manufacturing

The mechanism of the hump formation during the laser wire feeding process has been investigated in this paper. A numerical model was established to analyze the heat transfer and melt flow of molten pool during process with or without hump formation. And effects of laser power, traverse speed, and wire feeding speed on hump formation were also investigated through such a numerical model. The results showed that, under the condition with high wire feeding speed, the molten metal flowed rapidly to the tail of the molten pool due to the impact force of droplet and the metal vapor recoil pressure. Simultaneously, due to the high speed of laser movement, the thin channel of the trough solidified prematurely under the effect of surface tension, which isolated the heat transfer of the molten pool, and then formed periodic humps. By comparative analysis, the numerical simulation results were in good agreement with the experimental results.