Numerical simulation of heat and mass transfer in laser directed energy deposition

In order to accurately predict the heat transfer and flow process of laser directed energy deposition, the numerical simulation of whole stage after the powder leaves the nozzle was carried out. First, the powder flow mode with laser body heat source in the first stage was established, and the average temperature and velocity of the powder at the convergence plane were obtained as 1300 K and 13 m/s, respectively. Based on this, the coupling model of heat flow between powder and substrate in the second stage is improved, and the influence of multiple source terms such as powder temperature, powder velocity, gas velocity, surface tension and thermal buoyancy is considered comprehensively. The evolution of the temperature and flow field of the cladding layer are analyzed in detail under the spatiotemporal variation, and it is clear that there are two convection currents with different clockwise directions in the molten pool, and the Marangoni convection occupies the main position. Finally, FeCrNiMo alloy powder was deposited on 42CrMo substrate, and its morphology, hardness and tensile strength in different directions were analyzed. The average height, width and depth deviations of the experiment and simulation are 17.3 %, 15.5 % and 22.9 %, respectively. The average strength of the tensile sample V2 prepared by the cladding layer is 11.8 % higher than that of the substrate.