Finite element simulation of machining Inconel 718 alloy including microstructure changes

Inducing thermo-mechanical loads during the machining of hard materials lead to the severe grain re fi nement and hardness variation into the machined surface. This variation signi fi cantly affects the performance and the service quality of the products. Inconel 718 superalloy is one of the dif fi cult-to- machine materials employed widely in aerospace industries and its surface characteristics after fi nal machining process is really important. The main objective of this study is to implement a reliable fi nite element (FE) model for orthogonal machining of Inconel 718 alloy and prediction of the microstructure changes during the process. At fi rst, experimental results of cutting forces, chip geometry and maximum temperature were taken into account to identify the most suitable material model out of the seven models found in the literature. Then, the FE numerical model was properly calibrated using an iterative procedure based on the comparison between simulated and experimental results. Moreover, a user subroutine was implemented in FE code to simulate the dynamic recrystallization and, consequently, to predict grain re fi nement and hardness variation during the orthogonal cutting of Inconel 718 alloy. Zener–Hollomon and Hall–Petch equations were employed to respectively predict the grain size and microhardness. In addition, the depth of the affected layer was controlled using the critical strain equation. As overall, a very good agreement has been found between the experimental and simulated results in term of grain size, microhardness and depth of the affected layer.