Constitutive modEliNg of the mechanical and tribological behaviors of addiTive manUfactuRed IncONel 718: application to machining simulation – CENTURION

Additive manufacturing (AM) combined with a subtractive process (such as machining) enables the creation of parts with high complexity, tight tolerances, and good surface finishing. AM enables complex geometries to be generated, while machining produces better geometric accuracy and surface finishing quality than AM. A recent review on AM and surface ?nishing processes highlighted the fact that the limited number of research works on AM parts surface ?nishing is not yet able to promote the adoption of AM by several industrial sectors for an efficient, sustainable and profitable use without compromising the product quality. Therefore, there are considerable research and development opportunities in this area.
This project is centred on AM using Selective Laser Melting (SLM) process followed by machining to produce high quality parts in Inconel 718, without applying post-heat treatment. This can be a challenge since heat treatment is usually applied to improve the mechanical properties of AM parts, and to relive the high residual stress (RS) levels in the Inconel 718. These RS are caused by the rapid cooling during AM. They can affect the machining process and also the mechanical behaviour of AM Inconel 718.
This project aims to develop an anisotropic constitutive and contact models, combined with an advanced numerical method to accurately simulate the machining process of SLM Inconel 718. The anisotropic constitutive model should be able to accurately predict the mechanical behaviour of SLM Inconel 718 in machining. Therefore, it should account for most influencing factors in both material flow stress and damage of SLM Inconel 718, including: strain-rate, temperature, state of stress (stress triaxiality and Lode parameters), microstructure and RS. Like the constitutive model, the contact model between the SLM Inconel 718 and the tool material is also essential for an accurate simulation of machining of this work material. This contact model should account for the contact conditions often observed in machining (high pressure and high temperature). These models together with the phase field approach used to simulate the material separation in machining will contribute for the development of an accurate numerical model of machining of AM Inconel 718. This model is used to investigate the influence of the machining process parameters on the machinability and surface integrity of SLM Inconel 718. Moreover, it also enables to determine the optimal set of machining parameters to obtain an enhanced functional performance and life of AM parts.
This project also aims to control of the RS state generated by SLM without applying post-heat treatment. This control can be achieved by using optimised SLM strategy and parameters, as well as using a heating plate installed on the production plate of SLM machine. This heating plate will allow to adjust the thermal gradients inherent to the SLM process, and therefore to control the microstructure and the RS. This project opens new perspectives for optimized hybrid additive/subtractive process applications.