Finite Element Modeling of Microstructure in Laser-Deposited Multiple Layer Inconel 718 Parts

Laser direct metal deposition (LDMD) process is becoming a cost-effective and sustainable alternative to the traditional manufacturing process. However, depending on the process conditions, the high cooling rate in LDMD can result in undesirable microstructure, which can affect the performance and functionality of the manufactured component. This article reports an investigation into the microstructure that arises from LDMD of a multilayered Inconel 718 on EN-43 mild steel substrate. Using the finite element analysis package ANSYS, the investigation focused on prediction of the grain size distribution in the deposited component as a consequence of its thermal history. In agreement with results from experimental examination, the results of the investigation predicted an increase in interdendric arm spacing from the bottom towards the top of the deposited wall. This characterizes a finer microstructure at the bottom of the wall, which progressively coarsens towards the top of the wall as more layers are deposited. This variation in grain sizes gradually tapers off to a steady level after a few layers. The present model provides a simple yet effective method to estimate the microstructure in LDMD encompassing wide range of materials.