Application-specific thermomechanical correlation of LPBF Inconel 718

Abstract

Laser Powder Bed Fusion (LPBF) enables the printing of structurally complex components in a relatively short time and at a reasonable cost, while maintaining a high level of quality. However, in order to obtain a sufficiently good material quality for critical parts, particularly in the aerospace industry, it is essential to establish a clear relationship between the manufacturing process, including a subsequent thermomechanical treatment, the resulting phase composition and microstructure, and the obtained mechanical characteristics. Inconel 718, a material frequently utilized in the aerospace industry, particularly for turbines and combustion chambers, was subjected to investigation. This material is typically subjected to various heat treatments, including double ageing and hot isostatic pressure. In this study, the effects of different heat treatment strategies in as-built LPBF Inconel 718 were investigated in order to optimize the material's performance. The phase evolution was examined by high-energy diffraction at the synchrotron DESY in Hamburg. Mechanical properties were tested on cylindrical samples produced with different inclinations to the working platform: The orientation of the samples was 0° (horizontal), 45° (diagonal) and 90° (vertical). The correlation between the optimised process parameters, the type of post-processing, the microstructures and phase distribution, and the resulting strength behaviour allows the identification of a process chain specifically for a particular application.