Local chemical instabilities in 20Cr-25Ni Nb-stabilised austenitic stainless steel induced by proton irradiation

JOURNAL OF NUCLEAR MATERIALS

卷:518

Article

Barcellini, C.¹  Harrison, R. W.²  Dumbill, S.³  Donnelly, S. E.²  Jimenez-Melero, E.¹ 

[1] Univ Manchester, Mat Performance Ctr, Sch Mat, Oxford Rd, Manchester M13 9PL, Lancs, England

[2] Univ Huddersfield, Sch Comp & Engn, Huddersfield HD1 3DH, W Yorkshire, England

[3] Natl Nucl Lab, Sellafield CA20 1PG, Seascale, England

关键词: Austenitic stainless steel;    Proton irradiation;    Radiation-induced segregation;    Transmission electron microscopy;    Advanced gas-cooled reactors;   

DOI  :  10.1016/j.jnucmat.2019.02.035

来源: Elsevier

【 摘 要 】

We have assessed the local solute redistribution at defect sinks in 20Cr-25Ni Nb-stabilised austenitic stainless steel after proton irradiation at three temperatures, i.e. 420, 460 and 500 degrees C, up to a maximum damage level of 0.8 dpa. This material is currently being used as cladding in Advanced Gas-cooled Reactors (AGR), and potential local Cr depletions would compromise its resistance to intergranular corrosion attack during wet storage of spent fuel elements. Irradiation induces the depletion of Cr, Fe and, to a lesser extent, Mn from grain boundaries, whereas Ni and Si become enriched at those locations. The elemental profiles are symmetric and primarily W-shaped at 420 degrees C, whereas at higher temperatures asymmetric and double-peaked profiles are also detected, most likely as a result of grain boundary migration. High-angle grain boundaries with a misorientation angle >= 40 degrees become mobile at 460 degrees C and especially at 500 degrees C, and also experience a relatively large solute redistribution, with local Cr contents in a significant number of boundaries falling below 12 wt% and profile widths >= 100 nm. However, coincidence site lattice boundaries (CSL) Sigma 3 boundaries prove to be resistant to Cr depletion and to boundary mobility. Local elemental patterns at radiation-induced dislocations seem to mimic those at grain boundaries, but do not trigger the formation of Ni3Si precipitates. Additionally, Ni and Si form a shell-like structure around the pre-existing Nb(C,N) precipitates, potentially leading to the transition into G-phase at higher damage levels. (C) 2019 Elsevier B.V. All rights reserved.

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