NSUF 23-4636: Stability of VN, TaN, and TaC MX-type Precipitates in Ferritic Steels under Neutron Radiation
A leading strategy for designing radiation resistant nuclear structural materials is engineering a high density of nanoscale precipitates to act as obstacles to dislocation motion and as sinks for radiation-induced defects. Therefore, designing high stability MX-type precipitates is imperative for next-generation ferritic-martensitic (FM) steels to improve their mechanical properties and radiation resistance. FM steels are nuclear structural materials candidates for various advanced reactor concepts, such as cladding in sodium cooled fast reactors, Traveling Wave Reactors, and small modular reactor concepts. The stability of various MX precipitates (including VN, TaN and TaC) under thermal ageing conditions have been investigated. However, there is still lack of understanding of their precipitate behaviors in a reactor environment. The objective of this project is to compare the stability of various MX precipitates (including VN, TaN and TaC) in ferritic model alloys in a reactor environment, and to identify the properties contributing to precipitate stability in reactor. The outcome of this proposal will provide guidance on next generation FM steels design with stable MX precipitate to optimize mechanical properties and irradiation resistance.
This work proposes to investigate various MX precipitate stability in neutron-irradiated ferritic steels. Three ferritic model alloys were designed, which have different MX precipitates: VN, TaN and TaC. These precipitates have average sizes of <20nm with number densities on the order of 10E21 m^-3. The alloys were irradiated in the High Flux Isotope Reactor at 490℃ to 7.4dpa. The stability of these MX precipitates after neutron irradiation will be investigated primarily using transmission electron microscopy, specifically size, number density, morphology, crystal structure and coherency with matrix. The collected data will be compared to the results prior to irradiation. Such data will provide understanding of precipitate evolution and stability for various MX-type precipitates under irradiation conditions. The proposed work is expected to be completed within 6 months of the award date.
The results of this study will promote understanding of MX-type precipitate evolution under reactor environments and provide insight on factors contributing to precipitate stability in FM steels under extreme conditions. This knowledge gained from this work can be directly applied to next generation FM steels design efforts for advanced reactor structural materials, impacting DOE-NE’s goal to “enable the deployment of advanced nuclear reactors”. The higher operating temperatures and lifetime doses anticipated for advanced reactor designs necessitate radiation resistant materials with superior radiation tolerance mechanical properties, like high temperature creep resistance. Optimizing FM steels by engineering MX precipitates would assist safe advanced reactor deployment.
Additional Info
| Field | Value |
|---|---|
| Abstract | A leading strategy for designing radiation resistant nuclear structural materials is engineering a high density of nanoscale precipitates to act as obstacles to dislocation motion and as sinks for radiation-induced defects. Therefore, designing high stability MX-type precipitates is imperative for next-generation ferritic-martensitic (FM) steels to improve their mechanical properties and radiation resistance. FM steels are nuclear structural materials candidates for various advanced reactor concepts, such as cladding in sodium cooled fast reactors, Traveling Wave Reactors, and small modular reactor concepts. The stability of various MX precipitates (including VN, TaN and TaC) under thermal ageing conditions have been investigated. However, there is still lack of understanding of their precipitate behaviors in a reactor environment. The objective of this project is to compare the stability of various MX precipitates (including VN, TaN and TaC) in ferritic model alloys in a reactor environment, and to identify the properties contributing to precipitate stability in reactor. The outcome of this proposal will provide guidance on next generation FM steels design with stable MX precipitate to optimize mechanical properties and irradiation resistance. This work proposes to investigate various MX precipitate stability in neutron-irradiated ferritic steels. Three ferritic model alloys were designed, which have different MX precipitates: VN, TaN and TaC. These precipitates have average sizes of <20nm with number densities on the order of 10E21 m^-3. The alloys were irradiated in the High Flux Isotope Reactor at 490℃ to 7.4dpa. The stability of these MX precipitates after neutron irradiation will be investigated primarily using transmission electron microscopy, specifically size, number density, morphology, crystal structure and coherency with matrix. The collected data will be compared to the results prior to irradiation. Such data will provide understanding of precipitate evolution and stability for various MX-type precipitates under irradiation conditions. The proposed work is expected to be completed within 6 months of the award date. The results of this study will promote understanding of MX-type precipitate evolution under reactor environments and provide insight on factors contributing to precipitate stability in FM steels under extreme conditions. This knowledge gained from this work can be directly applied to next generation FM steels design efforts for advanced reactor structural materials, impacting DOE-NE’s goal to “enable the deployment of advanced nuclear reactors”. The higher operating temperatures and lifetime doses anticipated for advanced reactor designs necessitate radiation resistant materials with superior radiation tolerance mechanical properties, like high temperature creep resistance. Optimizing FM steels by engineering MX precipitates would assist safe advanced reactor deployment. |
| Award Announced Date | 2023-06-01T09:04:23.26 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Kory Linton |
| Irradiation Facility | None |
| PI | Emily Proehl |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |