Abstract
The electron beam melting (EBM) process is an attractive additive manufacturing technology that can be applied to a number of different materials. However, fabrication of each material requires tweaking and identifying optimal processing parameters. In this study, process parameters were successively varied to identify a processing regime to fabricate the nickel-base (Ni-base) superalloy Haynes 282. Key parameters to minimize porosity and mitigate the potential for cracking were beam velocity, beam current, hatch spacing, line order, and beam focus. Overall, the EBM process window produced a combination of promising microstructure and 99.5% dense material with no observable cracking. Electron backscatter diffraction revealed a crystallographic texture along the [001] direction of the cube orientation aligned with the build direction. Within the grain interiors of the as-fabricated material were observed uniformly distributed γ′ precipitates with a size distribution ranging from ~80 nm spherical to ~190 nm cuboidal particles with an average particle size of ~128 nm. Grain boundary carbides were observed in two morphologies: blocky and thin film–like. Hardness and tensile testing of the as-fabricated EBM material indicated a 10% higher hardness and slightly lower tensile strength compared with the as-annealed wrought form of the Haynes 282 alloy. The EBM alloy exhibited pronounced ductility except at T > 600 °C perpendicular to the build direction. Annealing based on standard wrought heat treatments showed that γ′ precipitates measuring 20–30 nm in average size can be achieved to improve the alloy's high-temperature performance.
Original language | English |
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Article number | 138607 |
Journal | Materials Science and Engineering: A |
Volume | 772 |
DOIs | |
State | Published - Jan 20 2020 |
Funding
Research was sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, and Office of Fossil Energy , Crosscutting Research Program, under contract DE-AC05-00OR22725 with UT-Battelle LLC. The microscopy was performed using instrumentation (FEI Talos F200× STEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities. T. S. Geer, T. M. Lowe, E. DiLoreto and D. W. Coffey assisted with the experimental work. The authors want to thank A. Forsythe, K. Kruger, and J.A. Haynes for providing comments on the results and manuscript. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- Carbides
- Cracks
- EBM
- Haynes 282
- Porosity
- Texture