Modeling and simulation of thermal field and solidification in laser powder bed fusion of nickel alloy IN625

Abstract

Finite element modeling and simulation of laser powder bed fusion process (L-PBF) provides physical insight about the laser processing that is often not possible or highly difficult by in-situ monitoring or in-process measurements. A three-dimensional (3D) thermal field especially into depth direction that is not visible by a thermal camera can be obtained by solving the 3D heat transfer problem. Furthermore, microstructure growth can be modelled to predict the direction of solidification in the fabricated part. This paper presents 3D Finite Element Method (FEM) based simulation models developed for laser processing of single- and multi-tracks with different energy density levels dependent upon process parameters such as laser power and scan velocity. This 3D L-PBF process model is validated with in-situ thermal measurements and further improved by utilizing predicted spattering of powder material which is in turn included as a stochastic heat loss in the 3D FEM model. Thermal gradients extracted from these simulations utilized to compute the directions in the resulting solidification which are found to be in reasonable agreements with experimental observations. Finally, a phase field method based post processing is applied on the thermal solution to simulate the nucleation phenomenon and columnar dendrite formation during solidification.