Abstract
In this work, a macro-micro VOF-PF (Volume of Fluid-Phase field) model is established to simulate the heat transfer, dendrite growth and Nb segregation during the laser IN718 deposition. According to calculated heat transfers, G increases, while Vp decreases, and the corresponding G×Vp decreases from top to bottom in the molten pool. The calculated the primary dendrite arm spacing (PDAS) using the PF model increases from top to bottom. Compared with other models, the calculated PDAS using the PF model considering the liquid-metal flow is closest to experiment measurements. During the dendrite growth, Nb is enriched in the interdendritic region, and finally is distributed in the droplet shape. The calculated actual solute distribution coefficient Cmin/Cmax decreases from 0.584 to 5.548 with the decrease of G×Vp, which follows the equilibrium solidification theory. According to dc/dy=G/ml, the liquidus slope ml is calculated as 0.05322wt.%/μm very close to the theoretical value 0.05394wt.%/μm. The simulated Nb concentrations in the matrix γ and Laves phases are 3.97wt.%, 13.3wt.% respectively, which are in good agreements with experimental 3.7wt.% and 13wt.%.
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