Neutron-Irradiated mechanical properties of wire arc additively manufactured grade 91 steel

T. M.Kelsy Green; Caleb Massey; Niyanth Sridharan; Annabelle Le Coq; Richard Howard; Kevin G. Field

doi:10.1016/j.jnucmat.2025.156189

Neutron-Irradiated mechanical properties of wire arc additively manufactured grade 91 steel

T. M.Kelsy Green
, Caleb Massey
, Niyanth Sridharan
, Annabelle Le Coq
, Richard Howard
, Kevin G. Field

Research output: Contribution to journal › Article › peer-review

Abstract

Wire arc additive manufacturing (WAAM) can result in material anisotropy because of the directionality of the additive process, but currently, little is known about the impact of additive-induced anisotropy on radiation-induced material degradation. To investigate the radiation effects as a function of the manufacturing process and to build directionality, three specimens of a WAAM-produced Grade 91 steel in three conditions (two as-printed samples in orientations both parallel [Z-direction] and perpendicular [X-direction] to the build direction, and one heat-treated sample oriented in the X-direction) were subjected to tensile testing before and after neutron irradiation in the High Flux Isotope Reactor to 0.75 and 2.1 displacements per atom (dpa) at a target temperature of 300°C. Tensile tests showed that the orientation of the as-printed specimens greatly affected the strain hardening capacity and elongation after necking before irradiation, and this anisotropy remained after irradiation. Regardless of orientation, the as-printed specimens had greater unirradiated yield strengths and, surprisingly, underwent greater irradiation hardening than the heat-treated specimen. The as-printed specimens initially had unirradiated yield strengths of ∼950 MPa and were further hardened by ∼400 MPa at 2.1 dpa, whereas the heat-treated specimen initially had an unirradiated yield strength of ∼730 MPa and was further hardened by ∼220 MPa at 2.1 dpa. These results underscore the importance of WAAM and post-processing parameters and specimen directionality on the irradiation response of ferritic/martensitic (FM) steels.

Original language	English
Article number	156189
Journal	Journal of Nuclear Materials
Volume	618
DOIs	https://doi.org/10.1016/j.jnucmat.2025.156189
State	Published - Jan 2026

Funding

This project was funded in part by a Rapid Turnaround Experiment (Project 22–4437) from the Nuclear Science User Facilities program of the US Department of Energy (DOE), Office of Nuclear Energy. Neutron irradiation in the High Flux Isotope Reactor is made possible by the Office of Basic Energy Sciences, DOE. The authors also acknowledge the University of Michigan-Ann Arbor College of Engineering for additional financial support. This project was funded in part by a Rapid Turnaround Experiment (Project 22–4437) from the Nuclear Science User Facilities program of the US Department of Energy (DOE), Office of Nuclear Energy. Neutron irradiation in the High Flux Isotope Reactor is made possible by the Office of Basic Energy Sciences, DOE. The authors also acknowledge the University of Michigan-Ann Arbor College of Engineering for additional financial support. The authors would like to thank Clay Morris and Patricia Tedder for sample logistics from the ORNL hot cell facility to the lab's low-activation facility, and Kory Linton for assisting with Nuclear Science User Facilities (NSUF) project oversight at ORNL. David Bryant assisted with capsule welding and certification for HFIR insertion. The efforts of Travis Dixon and Jesse Werden are also acknowledged for sample handling and mechanical testing. Finally, the authors would like to acknowledge Stephanie Curlin for performing the SiC dilatometry analysis. This manuscript has been authored in-part 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 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

Ferritic/Martensitic Steels
Grade 91
Mechanical properties
Neutron irradiation
Wire arc additive manufacturing (WAAM)

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10.1016/j.jnucmat.2025.156189

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title = "Neutron-Irradiated mechanical properties of wire arc additively manufactured grade 91 steel",

abstract = "Wire arc additive manufacturing (WAAM) can result in material anisotropy because of the directionality of the additive process, but currently, little is known about the impact of additive-induced anisotropy on radiation-induced material degradation. To investigate the radiation effects as a function of the manufacturing process and to build directionality, three specimens of a WAAM-produced Grade 91 steel in three conditions (two as-printed samples in orientations both parallel [Z-direction] and perpendicular [X-direction] to the build direction, and one heat-treated sample oriented in the X-direction) were subjected to tensile testing before and after neutron irradiation in the High Flux Isotope Reactor to 0.75 and 2.1 displacements per atom (dpa) at a target temperature of 300°C. Tensile tests showed that the orientation of the as-printed specimens greatly affected the strain hardening capacity and elongation after necking before irradiation, and this anisotropy remained after irradiation. Regardless of orientation, the as-printed specimens had greater unirradiated yield strengths and, surprisingly, underwent greater irradiation hardening than the heat-treated specimen. The as-printed specimens initially had unirradiated yield strengths of ∼950 MPa and were further hardened by ∼400 MPa at 2.1 dpa, whereas the heat-treated specimen initially had an unirradiated yield strength of ∼730 MPa and was further hardened by ∼220 MPa at 2.1 dpa. These results underscore the importance of WAAM and post-processing parameters and specimen directionality on the irradiation response of ferritic/martensitic (FM) steels.",

keywords = "Ferritic/Martensitic Steels, Grade 91, Mechanical properties, Neutron irradiation, Wire arc additive manufacturing (WAAM)",

author = "Green, \{T. M.Kelsy\} and Caleb Massey and Niyanth Sridharan and Coq, \{Annabelle Le\} and Richard Howard and Field, \{Kevin G.\}",

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doi = "10.1016/j.jnucmat.2025.156189",

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volume = "618",

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T1 - Neutron-Irradiated mechanical properties of wire arc additively manufactured grade 91 steel

AU - Green, T. M.Kelsy

AU - Massey, Caleb

AU - Sridharan, Niyanth

AU - Coq, Annabelle Le

AU - Howard, Richard

AU - Field, Kevin G.

PY - 2026/1

Y1 - 2026/1

N2 - Wire arc additive manufacturing (WAAM) can result in material anisotropy because of the directionality of the additive process, but currently, little is known about the impact of additive-induced anisotropy on radiation-induced material degradation. To investigate the radiation effects as a function of the manufacturing process and to build directionality, three specimens of a WAAM-produced Grade 91 steel in three conditions (two as-printed samples in orientations both parallel [Z-direction] and perpendicular [X-direction] to the build direction, and one heat-treated sample oriented in the X-direction) were subjected to tensile testing before and after neutron irradiation in the High Flux Isotope Reactor to 0.75 and 2.1 displacements per atom (dpa) at a target temperature of 300°C. Tensile tests showed that the orientation of the as-printed specimens greatly affected the strain hardening capacity and elongation after necking before irradiation, and this anisotropy remained after irradiation. Regardless of orientation, the as-printed specimens had greater unirradiated yield strengths and, surprisingly, underwent greater irradiation hardening than the heat-treated specimen. The as-printed specimens initially had unirradiated yield strengths of ∼950 MPa and were further hardened by ∼400 MPa at 2.1 dpa, whereas the heat-treated specimen initially had an unirradiated yield strength of ∼730 MPa and was further hardened by ∼220 MPa at 2.1 dpa. These results underscore the importance of WAAM and post-processing parameters and specimen directionality on the irradiation response of ferritic/martensitic (FM) steels.

AB - Wire arc additive manufacturing (WAAM) can result in material anisotropy because of the directionality of the additive process, but currently, little is known about the impact of additive-induced anisotropy on radiation-induced material degradation. To investigate the radiation effects as a function of the manufacturing process and to build directionality, three specimens of a WAAM-produced Grade 91 steel in three conditions (two as-printed samples in orientations both parallel [Z-direction] and perpendicular [X-direction] to the build direction, and one heat-treated sample oriented in the X-direction) were subjected to tensile testing before and after neutron irradiation in the High Flux Isotope Reactor to 0.75 and 2.1 displacements per atom (dpa) at a target temperature of 300°C. Tensile tests showed that the orientation of the as-printed specimens greatly affected the strain hardening capacity and elongation after necking before irradiation, and this anisotropy remained after irradiation. Regardless of orientation, the as-printed specimens had greater unirradiated yield strengths and, surprisingly, underwent greater irradiation hardening than the heat-treated specimen. The as-printed specimens initially had unirradiated yield strengths of ∼950 MPa and were further hardened by ∼400 MPa at 2.1 dpa, whereas the heat-treated specimen initially had an unirradiated yield strength of ∼730 MPa and was further hardened by ∼220 MPa at 2.1 dpa. These results underscore the importance of WAAM and post-processing parameters and specimen directionality on the irradiation response of ferritic/martensitic (FM) steels.

KW - Ferritic/Martensitic Steels

KW - Grade 91

KW - Mechanical properties

KW - Neutron irradiation

KW - Wire arc additive manufacturing (WAAM)

UR - https://www.scopus.com/pages/publications/105017807432

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DO - 10.1016/j.jnucmat.2025.156189

M3 - Article

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SN - 0022-3115

VL - 618

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

M1 - 156189

ER -

Neutron-Irradiated mechanical properties of wire arc additively manufactured grade 91 steel

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