High-performance Ni-based superalloy 718 fabricated via arc plasma directed energy deposition

Ni-based superalloy 718 fabricated via arc plasma direct energy deposition (IN718 AP-DED) exhibit a limited response to heat treatment due to its coarse primary microstructure and interdendritic segregation, which may prevent its use in high-integrity applications. Thus, dedicated heat treatments for IN718 AP-DED must possess a homogenization temperature as high as possible to significantly dissolve the eutectics and increase the γ′′-former elements in solid-solution. The present work proposed heat treatments for IN718 AP-DED (homogenization – 1050, 1100, 1142, and 1185 °C / 2 h – followed by aging – 718 °C / 8 h, cooling at 56 °C / h, and 621 °C / 8 h). The as-built IN718 AP-DED showed the typical coarse and oriented (cube texture) microstructure with eutectics (Laves and MC-typical carbides) in the interdendritic region, which were significantly dissolved during the homogenization, promoting a high-volume fraction of hardening phase (γ′′ and γ′) and outstanding quasi-static mechanical properties after the aging step. The present work showed that IN718 AP-DED mechanical properties can be optimized through dedicated heat treatments, meeting the ductility and yield strength requirements (room temperature) of AMS 5662. Furthermore, the heat treatments did not alter the grain morphology and texture aspect, inducing a lower Young's modulus compared to the non-oriented material.

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Funding Information: The authors acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Beamtime was allocated for proposal I-20210986 EC. This activity has received funding from the European Institute of Innovation and Technology (EIT) Raw Materials through the project Smart WAAM: Microstructural Engineering and Integrated Non-Destructive Testing. YZ acknowledges the National Natural Science Foundation of China (51601091), the Natural Science Foundation of Jiangsu Province (BK 20160826), the Six Talent Peaks Project of Jiangsu Province (2017-XCL-051), the Fundamental Research Funds for the Central Universities (30917011106), and Key Research and Development Plan of Jiangsu Province (BE2020085). Institut Pprime gratefully acknowledges “Contrat de Plan Etat - Région Nouvelle-Aquitaine (CPER)” as well as the “Fonds Européen de Développement Régional (FEDER)” for their financial support to part of the reported work. Publisher Copyright: © 2024 The Authors

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Additive manufacturing Directed energy deposition Heat treatment Inconel 718 Wire and arc additive manufacturing Biomedical Engineering General Materials Science Engineering (miscellaneous) Industrial and Manufacturing Engineering SDG 9 - Industry, Innovation, and Infrastructure