Process-Induced History Effects on the Mechanical Behavior of Additively Manufactured IN718 Alloys

The design complexities with advancements in technology limit the operational efficiency and conventional manufacturing ability of Nickel-based superalloy 718 (IN718). Additive manufacturing (AM) can overcome these drawbacks by producing near-net shape components; however, a thorough understanding of mechanical behavior at elevated temperatures and different loading conditions (i.e., tension and compression) is required before its actual use. In this work, process-induced history effects on the mechanical behavior in an additively manufactured IN718 alloy were investigated. In particular, two different heat treatment routes were chosen to tailor the microstructure by having the specific dissolution of precipitated phases. Quasi-static (QS) and creep experiments were performed in both as-build and postprocessed conditions. The build directions and the nature of the phases present were observed to be the governing factors. Results showed that the horizontal orientation had higher yield strength compared to the vertical orientation, irrespective of loading condition. Compression and tensile creep experiments indicated that the creep life was dependent on the orientation of δ/Laves phases. Furthermore, a tension-compression asymmetry was observed in both QS and creep testing. Overall, postprocessing proved to be advantageous in improving mechanical behavior and reducing the anisotropy related to the build direction.