Prediction of the primary dendritic arm spacing in the laser metal deposition of Inconel 718 superalloy using the numerical and experimental techniques

In order to obtain the knowledge about the formation of the oriented structure in the additive manufacturing process, it is required to gain an accurate understanding about the formation and growth of grains. Hence, in this paper, the simulation of laser metal deposition was performed by the volume of fluid technique to predict the primary dendritic arm spacing, fluid flows, and geometry of the deposited layer. Moreover, the laser metal deposition of the Inconel 718 superalloy was performed experimentally to verify the results of simulation. From the results of simulation, a maximum error of about 8% was observed in the prediction of the geometry of the deposited layer. In addition, the difference between the value of primary dendritic arm spacing in the experimental and simulation results was about 14%. The results have also shown that a cellular dendritic structure was formed when the ratio of the temperature gradient to the cooling rate was more than 9 × 108, while when this ratio was less than 9 × 108, a columnar dendritic structure was formed. The results of simulations and experiments showed that an increase in the laser power from 350 to 450 W led to an improvement of about 9.5% in the size of primary dendrite arms due to the reduction in the temperature gradient, while the increase in the scanning speed from 3 to 5 mm/s resulted in a reduction of about 21% in the size of primary dendrite arms due to the faster cooling rate.