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Wire + Arc Additively Manufactured Inconel 718: Effect of postdeposition heat treatments on microstructure and tensile properties

Research output: Contribution to journalArticle

Original languageEnglish
Article number108157
Number of pages13
JournalMaterials and Design
Volume183
Early online date24 Aug 2019
DateAccepted/In press - 23 Aug 2019
DateE-pub ahead of print (current) - 24 Aug 2019
DatePublished - 5 Dec 2019

Abstract

Wire + Arc Additive Manufacturing (WAAM) can be used to create large free-form components out of specialist materials such as nickel-base superalloys. Inconel (IN) 718 is well suited for the WAAM process due to its excellent weldability. However, during deposition, WAAM IN718 is susceptible to micro-segregation, leading to undesirable Laves phase formation in the interdendritic regions. Further, the WAAM process encourages columnar grain growth and the development of a strong fibre texture, leading to anisotropy in grain structure. This unfavourable microstructure can be addressed through specialised post-deposition homogenisation heat treatments. A new modified heat treatment was found to be effective in dissolving Laves phase, whereas a standard treatment precipitated δ phase. Tensile test results revealed that Laves and δ phases lead to low ductility when present in a precipitation-hardened matrix. The modified heat treatment also reduced the anisotropy in grain structure, leading to almost isotropic elevated temperature tensile properties, which meet minimum specifications for conventional cast but not for wrought material. Specialised post-deposition heat treatments, which address the unique microstructure of WAAM IN718, are crucial to achieving optimal mechanical properties.

    Research areas

  • Additive manufacturing, Nickel-base superalloy, Heat treatment, Microstructure, Tensile properties, Elevated temperature

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via Elsevier at https://doi.org/10.1016/j.matdes.2019.108157 . Please refer to any applicable terms of use of the publisher.

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