Numerical Modelling of the Gas-Powder Flow During the Laser Metal Deposition for Additive Manufacturing

As one of the most popular additive manufacturing (AM) technologies in the aerospace industry, laser metal deposition (LMD) employs moving laser to melt the coaxially ejected metal powders near the laser focal point, forms a molten pool on the substrate and consequently traps the powders and solidifies the tracks to construct the components with complex geometry layer-by-layer. The mechanical properties and functionality-related performance of the deposited components by LMD depend on the factors such as metal powder's material/shape, supply status of powders and gas, laser-related manufacturing parameters. According to these influencing factors, there are 4 sub-processes to be modelled in sequence to realize holistic LMD modelling: (1) CFD simulation of the gas-powder flow; (2) laser-powders interaction; (3) formation of molten pool due to laser irradiation with mass and heat addition; (4) solidification of molten pool with deposited metal powders and formed solid track. In this paper, gas-powder flow within the internal passages of laser deposition head and then ejecting from the nozzles' tips were modelled and analyzed to give a well-depicted image of the related key physics during the LMD process. An in-depth study of the gas-powder flow in LMD via numerical simulation could give a better understanding of subsequent formation mechanism of molten pool and deposited tracks, which will eventually offer more controllable and optimized processing parameter sets to improve the functionality-related performance of LMDed parts.