Low-Dose Neutron Irradiation Effects on Mechanical Properties of Additively Manufactured 316SS
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
As part of an effort to qualify laser powder bed fusion (LPBF) SS-316H material for use in advanced reactors, the US Department of Energy Office of Nuclear Energy’s Advanced Materials and Manufacturing Technologies (AMMT) program recently initiated a three-phase irradiation campaign on LPBF SS-316H to assess modes of material degradation at elevated temperatures (400–600°C) to irradiation doses up to 10 dpa. The first of three irradiations—conducted in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory—assessed the level of degradation of one heat of LPBF SS-316H material produced using at least two different representative processing parameters and post-build heat treatments in comparison with reference wrought material. In FY 2023, 20 irradiation vehicles comprising 240 test specimens were inserted in HFIR, and post-irradiation examination was recently completed on the lower-dose (2 dpa) specimens. Following sample disassembly and inventory, measurements of SiC thermometry specimens indicated that the irradiation was successful at reaching the target irradiation temperature within 16%. At least one rabbit in each condition successfully reached within 20°C of the target irradiation temperature. At least one irradiation capsule deviated from the target irradiation temperature of 600°C by approximately 88°C. Therefore, the test matrix was altered to include testing at 400°C, 500°C, and 600°C to provide fewer statistics but a larger breadth of test conditions to elucidate temperature-dependent performance vs. unirradiated conditions. Tensile testing of the LPBF SS-316H specimens revealed no significant change in ductility for stress-relieved specimens when these specimens were tested at elevated temperatures following irradiation, although significant ductility loss was noted for solution-annealed LPBF SS-316H specimens at all irradiation conditions. The stress-relieved and solution-annealed LPBF SS-316H showed similar postirradiation ductility. No significant changes in postirradiation strength or ductility were noted for wrought SS-316H, except for marginal increases in yield strength at an irradiation temperature of approximately 400°C. Conversely, the ductility of the advanced wrought Alloy 709 decreased following all irradiation conditions to a level close to that of the stress-relieved SS-316H. In addition to changes in ductility following irradiation, room temperature investigations of LPBF and wrought SS-316H revealed differential levels of fracture toughness change following irradiation. For the wrought SS-316H material, fracture toughness decreased by approximately 30%, whereas for the LPBF SS-316H material, fracture toughness only showed marginal changes vs. unirradiated measured values. Even with the drastic decrease in wrought SS-316H fracture toughness, the wrought material retained higher fracture toughness than any of the LPBF SS-316H material conditions, regardless of postbuild heat treatment or specimen orientation.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Materials & Manufacturing Technologies Office (AMMTO)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 2586918
- Report Number(s):
- ORNL/SPR--2025/3773
- Country of Publication:
- United States
- Language:
- English
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