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Title: He Transport and Fate of Tempered Martensitic Steels: Summary of Recent TEM Observations

Abstract

As an extension of prior work [1-4], we summarize recent observations made on a He-implanted tempered martensitic steel (TMS), F82H mod 3, irradiated in the HFIR, in both as-tempered (AT) and cold-worked (CW) conditions. A novel implantation technique was used to uniformly inject He into 3-mm diameter TEM discs to depths ranging from ≈ 5-8 µm. The He is generated by two-step transmutation reactions in Ni contained in a NiAl coating layer adjacent to paired 3 mm TEM discs. NiAl layers from 1 to 4 μm thick produced He/dpa ratios between 5 and 40 appm/dpa. The irradiations were at temperatures of 300, 400 and 500°C from 3.9 to 9 dpa and 90 to 380 appm He. Electron transparent samples were prepared by a cross-sectional thinning technique that allowed investigating microstructural evolution over a range of implantation depths. Irradiation of the AT alloy to 9 dpa at 500°C and 380 appm He resulted in relatively large, faceted cavities, that are likely voids, along with a much higher density of smaller He bubbles. The cavities were most often aligned in pearl necklace like strings, presumably due to their formation on pre-existing dislocations. A finer distribution of cavities was also present on precipitatemore » interfaces, lath and grain boundaries. Nine dpa irradiations that produced 190 appm He resulted in a somewhat more random distribution and lower density of smaller matrix cavities; but lower He levels had a less noticeable effect on bubbles in the lath and precipitate boundaries. Corresponding irradiations of the CW F82H produced a larger number of smaller cavities. Irradiation of the AT alloy to 3.9 dpa and 90 ppm He at 400°C produced a similar cavity population to that observed at 500°C at 190 appm He, while the corresponding cavities at 500°C are slightly larger and more numerous at 380 appm He. The cavity strings were less obvious for the 400°C irradiations, and the bubble distribution appeared to be more random. No cavities were observed in the case of the 300°C irradiations. Overall the cavity number densities compare favorably with those previously reported [4], but details, including size distributions, are still under investigation. Dislocation structures were complex and varied greatly as a function of irradiation dose and temperature, and will be more thoroughly characterized in the next phase of the work.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1072915
Report Number(s):
PNNL-19198
AT6020100
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English

Citation Formats

Edwards, Danny J, Kurtz, Richard J, Odette, G Robert, and Yamamoto, Takuya. He Transport and Fate of Tempered Martensitic Steels: Summary of Recent TEM Observations. United States: N. p., 2010. Web. doi:10.2172/1072915.
Edwards, Danny J, Kurtz, Richard J, Odette, G Robert, & Yamamoto, Takuya. He Transport and Fate of Tempered Martensitic Steels: Summary of Recent TEM Observations. United States. doi:10.2172/1072915.
Edwards, Danny J, Kurtz, Richard J, Odette, G Robert, and Yamamoto, Takuya. Fri . "He Transport and Fate of Tempered Martensitic Steels: Summary of Recent TEM Observations". United States. doi:10.2172/1072915. https://www.osti.gov/servlets/purl/1072915.
@article{osti_1072915,
title = {He Transport and Fate of Tempered Martensitic Steels: Summary of Recent TEM Observations},
author = {Edwards, Danny J and Kurtz, Richard J and Odette, G Robert and Yamamoto, Takuya},
abstractNote = {As an extension of prior work [1-4], we summarize recent observations made on a He-implanted tempered martensitic steel (TMS), F82H mod 3, irradiated in the HFIR, in both as-tempered (AT) and cold-worked (CW) conditions. A novel implantation technique was used to uniformly inject He into 3-mm diameter TEM discs to depths ranging from ≈ 5-8 µm. The He is generated by two-step transmutation reactions in Ni contained in a NiAl coating layer adjacent to paired 3 mm TEM discs. NiAl layers from 1 to 4 μm thick produced He/dpa ratios between 5 and 40 appm/dpa. The irradiations were at temperatures of 300, 400 and 500°C from 3.9 to 9 dpa and 90 to 380 appm He. Electron transparent samples were prepared by a cross-sectional thinning technique that allowed investigating microstructural evolution over a range of implantation depths. Irradiation of the AT alloy to 9 dpa at 500°C and 380 appm He resulted in relatively large, faceted cavities, that are likely voids, along with a much higher density of smaller He bubbles. The cavities were most often aligned in pearl necklace like strings, presumably due to their formation on pre-existing dislocations. A finer distribution of cavities was also present on precipitate interfaces, lath and grain boundaries. Nine dpa irradiations that produced 190 appm He resulted in a somewhat more random distribution and lower density of smaller matrix cavities; but lower He levels had a less noticeable effect on bubbles in the lath and precipitate boundaries. Corresponding irradiations of the CW F82H produced a larger number of smaller cavities. Irradiation of the AT alloy to 3.9 dpa and 90 ppm He at 400°C produced a similar cavity population to that observed at 500°C at 190 appm He, while the corresponding cavities at 500°C are slightly larger and more numerous at 380 appm He. The cavity strings were less obvious for the 400°C irradiations, and the bubble distribution appeared to be more random. No cavities were observed in the case of the 300°C irradiations. Overall the cavity number densities compare favorably with those previously reported [4], but details, including size distributions, are still under investigation. Dislocation structures were complex and varied greatly as a function of irradiation dose and temperature, and will be more thoroughly characterized in the next phase of the work.},
doi = {10.2172/1072915},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2010},
month = {2}
}

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