Fleming, Tristan G;
Rees, David Tien;
Marussi, Sebastian;
Connolley, Thomas;
Atwood, Robert C;
Jones, Martyn A;
Fraser, James M;
... Lee, Peter D; + view all
(2023)
In situ correlative observation of humping-induced cracking in directed energy deposition of nickel-based superalloys.
Additive Manufacturing
, 71
, Article 103579. 10.1016/j.addma.2023.103579.
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Abstract
Directed energy deposition (DED) is a promising additive manufacturing technique for repair; however, DED is prone to surface waviness (humping) in thin-walled sections, which increases residual stresses and crack susceptibility, and lowers fatigue performance. Currently, the crack formation mechanism in DED is not well understood due to a lack of operando monitoring methods with high spatiotemporal resolution. Here, we use inline coherent imaging (ICI) to optically monitor surface topology and detect cracking in situ, coupled with synchrotron X-ray imaging for observing sub-surface crack healing and growth. For the first time, ICI was aligned off-axis (24° relative to laser), enabling integration into a DED machine with no alterations to the laser delivery optics. We achieved accurate registration laterally (<10 µm) and in depth (<3 µm) between ICI measurements and the laser beam position using a single-element MEMS scanner and a custom calibration plate. ICI surface topology is verified with corresponding radiographs (correlation >0.93), directly tracking surface roughness and waviness. We intentionally seed humping into thin-wall builds of nickel super-alloy CM247LC, locally inducing cracking in surface valleys. Crack openings as small as 7 µm were observed in situ using ICI, including sub-surface signal. By quantifying both humping and cracking, we demonstrate that ICI is a viable tool for in situ crack detection.
| Type: | Article |
|---|---|
| Title: | In situ correlative observation of humping-induced cracking in directed energy deposition of nickel-based superalloys |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.addma.2023.103579 |
| Publisher version: | https://doi.org/10.1016/j.addma.2023.103579 |
| Language: | English |
| Additional information: | © 2023 The Author(s). Published by Elsevier B.V. under a Creative Commons license (http://creativecommons.org/licenses/by/4.0/). |
| Keywords: | Inline coherent imaging, Directed energy deposition, Synchrotron X-ray imaging, Humping and cracking defects, In situ monitoring |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10169810 |
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