Journal
SCRIPTA MATERIALIA
Volume 194, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.scriptamat.2020.113661
Keywords
Additive manufacturing; Electron beam melting; Superalloy; Nano-scale; Precipitation
Categories
Funding
- Medium-Sized Centre funding scheme - National Research Foundation, Prime Minister's Office, Singapore
- French METSA network [FR3507]
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The study investigates the nanometer-scale microstructural evolution in an additively manufactured Re-free Ni-based superalloy with single crystal compositions. It finds that nano-scale primary γ' precipitation leads to exceptional microhardness, and ultra-fine γ' precipitates are observed at the bottom layers of the samples, contradicting previous consensus on hierarchical γ' phase evolution in such alloys.
The nanometer-scale (nano-scale) microstructural evolution in an additively manufactured Re-free Ni-based superalloy, with single crystal compositions, is investigated through field emission scanning electron microscopy, transmission electron microscopy, and atom probe tomography. We find that nano-scale primary. gamma' precipitation occurs in the fine as-built microstructure, leading to an exceptional microhardness of 480.0 +/- 6.7 HV at room temperature. Presence of ultra-fine. gamma' precipitates, similar to 20 nm in size, is observed in the bottom few layers of the as-built samples, which is hitherto undocumented and contrary to the widespread consensus regarding hierarchical. gamma' phase evolution in additively manufactured Ni-based superalloys. Moreover, considerable precipitation of tantalum-rich C14 Laves phase at the grain boundaries and interdendritic regions in the as-built samples emphasizes the need for additive manufacturing specific alloy design. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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