Thermo-mechanical simulation of annealing heat treatment of Ni-based GH4099 superalloy made by laser powder bed fusion

Laser powder bed fusion (LPBF) additive manufacturing (AM) unavoidably generates residual stresses due to sharp thermal gradients and the strong mechanical constraints of the substrate. These stresses can lead to large warpages and cracking of AM builds, compromising their qualification. Annealing heat treatment (HT) after LPBF fabrication is an efficient solution for residual stress relaxation, allowing for the development of visco-strains above the annealing temperature. Thereby, this work is focused on the thermo-mechanical simulation of the post-HT of Ni-based GH4099 superalloy components fabricated by LPBF. To this end, several bridge structures are manufactured by LPBF, and various annealing HT conditions are analyzed. After cutting from the substrate, the warpage of all the AM-parts is measured using a 3D-scanner. The in-house software package for the numerical simulation of both the AM and the HT processes first is calibrated by matching the experimental measurements. Next, the numerical tool is used to investigate the effect of different annealing conditions (e.g. varying temperature and dwell time) on the relaxation of the residual stresses and warpage. A roadmap to select the optimal annealing parameters is established considering the actual size of the AM-components.