Numerical simulation and experimental validation of melting and solidification process in selective laser melting of IN718 alloy

Abstract

A three-dimensional numerical model is developed to investigate the melting and solidification process during the Selective Laser Melting (SLM) of IN718. The model utilizes the effective medium approach to solve the heat transfer and melt-flow dynamics within the melt-pool in a computationally efficient manner. In addition, the model replaces the built-in linear solidification function in commercial code ANSYS Fluent with a self-written non-linear solidification function in order to better describe the melt-pool formation during the SLM process. The simulation results obtained for the depth and width of the melt-pool are compared with the experimental data reported in the literature. Moreover, the simulated melt-pool length defined by the liquid-solid phase transition point of the melt-pool trailing edge is compared with the experimental observations obtained using a self-built in-situ inspection system. For the simulated melt-pool depth and width, no significant difference is found between the non-linear and linear models for the solidification behavior of IN718. However, the non-linear model provides a better prediction of the melt-pool length than the linear solidification function. Many studies have shown that the solid-liquid transition in the melting range of the material during cooling plays an important role in determining both the melt-pool length and the cooling rate of the SLM parts. As a result, the effects of the non-linear solidification behavior of IN718 are important not only in determining the melt-pool formation, but also in governing the liquid-solid transition process at the melt-pool tailing edge, which is one of the most important factors affecting the microstructure and residual stress accumulation of SLM printed parts.