Research On The Flow Field And Mass Transfer Of Tiny Molten Pool During Selective Laser Melting Of Inconel 718

A transient three-dimensional powder-scale model and an experiment have been established for investigating the flow field and mass transfer within the molten pool during selective laser melting(SLM)Inconel718 alloy by Ansys Fluent.Some important physical phenomena,such as a transition from powder to solid,nonlinearities produced by temperature-dependent material properties and fluid flow,were taken into account in the calculation.In addition,an experiment are designed to verify the result of the simulation.The simulation results reveal that the temperature contour plots from top view were observed somewhat stretched to a comet-shaped tail along the laser scanning direction and the temperature distribution was symmetrical in X-Y and Y-Z sections.Due to the introduction of the Gaussian distribution laser heat source,large temperature gradient are formed within the laser-induced melt pool.The temperature gradient will lead to a surface tension gradient.Marangoni effect,which is caused by the surface tension gradients,is the major driving force for the melt flow.The melt flow velocity is closely related to the laser scanning parameters.The velocity and the vortex size increased with increasing laser power or decreasing scan speed and scan hatch.Moreover,compare to the single-track scan strategy,the melt flow velocity within the molten pool is faster during multi-tracks scan strategy because of the previous fabricated track's thermal effects.Finally,the experiment prove the melt flow is indeed exist within the tiony molten pool.An experiment is designed to analyze the distribution of element Nb,The results show that the content of Nb decreased and the distribution is more uniform with increasing laser power or decreasing scan speed and scan hatch,the phenomenon of segregation is more unconspicuous.During the solidification of selective laser melting,the high cooling rate stop the solute diffusion in the solid and liquid phases?Thus,the distribution of Nb elements in the solid phase after solidification is similar to that of the liquid phase Combining the results of simulation and experiment,it showed that tthe result of experiment have a great agreement with the result of simulation.