TEM/STEM study of Zircaloy-2 with protective FeAl(Cr) layers under simulated BWR environment and high-temperature steam exposure

JOURNAL OF NUCLEAR MATERIALS

卷:502

Article

Park, Donghee¹  Mouche, Peter A.¹  Zhong, Weicheng¹  Mandapaka, Kiran K.²  Was, Gary S.²  Heuser, Brent J.¹ 

[1] Univ Illinois, Dept Nucl Radiol & Plasma Engn, Urbana, IL 61801 USA

[2] Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48109 USA

关键词: LWR cladding;    Oxidation;    Corrosion;    Protective coatings;    FeCrAl;    TEM;   

DOI  :  10.1016/j.jnucmat.2018.01.055

来源: Elsevier

【 摘 要 】

FeAl(Cr) thin-film depositions on Zircaloy-2 were studied using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) with respect to oxidation behavior under simulated boiling water reactor (BWR) conditions and high-temperature steam. Columnar grains of FeAl with Cr in solid solution were formed on Zircaloy-2 coupons using magnetron sputtering. NiFe2O4 precipitates on the surface of the FeAl(Cr) coatings were observed after the sample was exposed to the simulated BWR environment. High-temperature steam exposure resulted in grain growth and consumption of the FeAl(Cr) layer, but no delamination at the interface. Outward Al diffusion from the FeAl(Cr) layer occurred during high-temperature steam exposure (700 degrees C for 3.6 h) to form a 100-nm-thick alumina oxide layer, which was effective in mitigating oxidation of the Zircaloy-2 coupons. Zr intermetallic precipitates formed near the FeAl(Cr) layer due to the inward diffusion of Fe and Al. The counterflow of vacancies in response to the Al and Fe diffusion led to porosity within the FeAl(Cr) layer. (c) 2018 Elsevier B.V. All rights reserved.

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