NSUF 18-1396: Microstructural Characterization of Radiation Tolerance of Advanced Joining Techniques for Oxide Dispersion Strengthened Steels under Ion Irradiation
The objective of this work is to examine the effect of high damage levels of radiation on the microstructure in ferritic oxide dispersion strengthened (ODS) steels joined by either friction stir welded (FSW) or additive friction stirred manufactured (AFSM). ODS alloys offer high strength, creep resistance as well as dimensional stability under irradiation, which makes them attractive candidates for structural and fuel cladding applications in advanced reactor concepts. The radiation tolerance is due to the high sink strength that arises from the high density of dispersoids (Y-Al-O or Y-Ti-O) throughout the matrix. However, with the addition of any welding process, the dispersoids are expected to coarsen due to an Ostwald ripening processing. To date there has been little examination of the effect of welding on radiation tolerance of ODS alloys, which represents a significant gap in knowledge necessary for the manufacturing and implementation of advanced fuel cladding. Furthermore, there has been no examination of the variation in weld parameters of FSW or the AFS technique at all, either of which may mitigate this coarsening relative to traditional practices and a comparison between these advanced joining methods will be required to test the efficacy of AFS joining. MA956 and 14YWT, the alloys of interest in this study, have been well characterized in the as-received and welded condition in terms of mechanical properties as well as dispersoid and grain behavior. From the unirradiated work, the coarsened dispersoids, as a result of welding, are expected to result in decreased strength and susceptibility to radiation tolerance due to the overall decreased sink strength. Therefore, additional data comparing both the as-received and welded material as a function of increasing dose at a variety of temperatures is necessary to determine the degree to which there is loss of radiation tolerance and by extension, mechanical properties. This project will optimize welding processes based upon the metric of radiation-tolerance, by irradiating both FSW and AFS in the joined and as received condition as a benchmark. Furthermore, a variety of heat inputs for FSW will be examined to determine best practices for FSW. This RTE will support the microstructure characterization of irradiations funded by NSUF RTE 17-1032. Previous work on this line of inquiry have suggested some potentially interesting reprecipitation mechanisms of dispersoids in welded than irradiated MA956, which may mitigate the deleterious effects of the of welding, but further exploration is necessary to understand the precise mechanisms. This project will provide a systematic understanding of the negative effects of advanced welding techniques on irradiated material performance, a novel and valuable area of growing interest to the Department of Energy Office of Nuclear Energy, as advanced clad materials are selected and eventually manufactured for Gen IV reactors.
Additional Info
| Field | Value |
|---|---|
| Abstract | The objective of this work is to examine the effect of high damage levels of radiation on the microstructure in ferritic oxide dispersion strengthened (ODS) steels joined by either friction stir welded (FSW) or additive friction stirred manufactured (AFSM). ODS alloys offer high strength, creep resistance as well as dimensional stability under irradiation, which makes them attractive candidates for structural and fuel cladding applications in advanced reactor concepts. The radiation tolerance is due to the high sink strength that arises from the high density of dispersoids (Y-Al-O or Y-Ti-O) throughout the matrix. However, with the addition of any welding process, the dispersoids are expected to coarsen due to an Ostwald ripening processing. To date there has been little examination of the effect of welding on radiation tolerance of ODS alloys, which represents a significant gap in knowledge necessary for the manufacturing and implementation of advanced fuel cladding. Furthermore, there has been no examination of the variation in weld parameters of FSW or the AFS technique at all, either of which may mitigate this coarsening relative to traditional practices and a comparison between these advanced joining methods will be required to test the efficacy of AFS joining. MA956 and 14YWT, the alloys of interest in this study, have been well characterized in the as-received and welded condition in terms of mechanical properties as well as dispersoid and grain behavior. From the unirradiated work, the coarsened dispersoids, as a result of welding, are expected to result in decreased strength and susceptibility to radiation tolerance due to the overall decreased sink strength. Therefore, additional data comparing both the as-received and welded material as a function of increasing dose at a variety of temperatures is necessary to determine the degree to which there is loss of radiation tolerance and by extension, mechanical properties. This project will optimize welding processes based upon the metric of radiation-tolerance, by irradiating both FSW and AFS in the joined and as received condition as a benchmark. Furthermore, a variety of heat inputs for FSW will be examined to determine best practices for FSW. This RTE will support the microstructure characterization of irradiations funded by NSUF RTE 17-1032. Previous work on this line of inquiry have suggested some potentially interesting reprecipitation mechanisms of dispersoids in welded than irradiated MA956, which may mitigate the deleterious effects of the of welding, but further exploration is necessary to understand the precise mechanisms. This project will provide a systematic understanding of the negative effects of advanced welding techniques on irradiated material performance, a novel and valuable area of growing interest to the Department of Energy Office of Nuclear Energy, as advanced clad materials are selected and eventually manufactured for Gen IV reactors. |
| Award Announced Date | 2018-05-17T10:58:42.363 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Elizabeth Getto |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1396 |