2018 Fiscal Year Annual Research Report
Irradiation effects on the performance of the alumina scale formed in FeCrAl ODS ferritic steels
| Project/Area Number |
18H05839
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| Allocation Type | Single-year Grants |
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| Research Institution | Tohoku University |
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Principal Investigator |
余 浩 東北大学, 金属材料研究所, 助教 (10825871)
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| Project Period (FY) |
2018-08-24 – 2020-03-31
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| Keywords | oxidation / FeCrAl ferritic steels / ODS / irradiation / alumina |
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| Outline of Annual Research Achievements |
In order to develop a reliable alumina film for FeCrAl oxide dispersion-strengthened (ODS) ferritic steels during irradiation environment, the irradiation influence on the alumina performance is worthy to be examined. The research is aimed at investigating the irradiation effects on the FeCrAl ODS ferritic steels with alumina scale. The purpose of this year is to investigate the oxidation behavior of FeCrAl ODS ferritic steels with Zr addition and various contents of excessive oxygen. Irradiation test will be conducted on next step. Zr and Ex. O added Fe-15Cr-7Al-0.5Y2O3 (wt.%) ODS ferritic steels were fabricated with mechanical alloying (MA). Arc-melted Y2O3-free samples was prepared to act as a comparative test. All the samples were oxidized at 900 oC and 1000 oC under air condition. Based on microstructure observation, alumina was demonstrated to dominate the oxide scales in all specimens. However, a noticeable difference was found in the oxidation kinetics, closely connected with the Zr and/or the excessive oxygen in alloy system. Related discussion and conclusion were given based on the experimental results, which is beneficial for the preparation of alumina scale for irradiation experiments.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
First year has been dedicated mainly on alloys fabrication and high temperature oxidation testing. Fe-15Cr-7Al-0.5Y2O3 (wt. %) ODS ferritic steels with and without Zr were fabricated with MA. Arc-melting was also used to fabricate the Y2O3-free samples. In order to understand the effect of excessive oxygen (Ex. O) on the oxidation behavior, 0.142 wt% and 0.241 wt% Ex. O added ODS ferritic steels were also mechanical alloyed. MA-ed powders were consolidated with spark plasma sintering (SPS) at 1150 oC and 50 MPa for 30min, followed by hot-rolling at 1150 oC. Oxidation testing was conducted at 900 oC and 1000 oC under air condition. The scale formed on surface was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA).
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| Strategy for Future Research Activity |
In second year, we continue working on microstructure characterization of the formed alumina scale, especially focusing on the distribution of Y-included oxide particles in the alumina scale via using the transmission electron microscope (TEM) observation. In addition, based on current results of oxidation testing, an appropriate pre-oxidation process will be done to form alumina scale with a certain thickness on all the samples. Then, the FeCrAl samples with alumina scale will be irradiated by using simulation ion irradiation technique in DuET, Kyoto University. After suffering from irradiation-processing, the alumina scale would be analyzed through corresponding microstructure characterization.
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