Significance Statement
Corrosion tests in flowing Pb-17Li eutectic (velocity 5 cm/s at 550 ºC, 1000 h) under a strong magnetic field (B = 1.7 T) were performed to study the RAFM steel (Eurofer) response in fusion conditions.
The results indicate that the magnetic field induces a faster crushing of martensite into the grains, a deeper dissolution of grain boundaries, an enhancement of the Fe and Cr mass transfer and a fast detachment of corrosion layers due to MHD effects.
Since the main mechanism of corrosion for Eurofer is the dissolution of iron and chromium in the Pb-Li eutectic liquid flow. The presence of the magnetic field intensifies the process, which in structural aspect has a multilevel character. Macroscopically, on the surface of steel, the presence of a high dissolution wave-like zone oriented in the flow direction and perpendicular to the magnetic field was observed (see figure); at the same time, the micro-structural analysis showed a strong corrosion attack not only at the grain boundaries, but also inside the grains leading to destruction of the martensitic matrix.
In the presence of the magnetic field the corrosion layer consists of a single phase with a constant Pb to Li ratio. Chromium and iron are introduced into the corrosion layer as separate aggregates or crystalline phases forming an inhomogeneous mixture with PbLi eutectic. The magnetic field increases the Cr and Fe mass transfer processes and produces a micro-hardness decrease close to the contact surface. The fast erosion is also caused by MHD effects.
Journal Reference
Journal of Nuclear Materials, Volume 465, 2015, Pages 633–639.
Carmona Gázquez1, T. Hernández1, F. Muktepavela2, E. Platacis3, A. Shishko3
[expand title=”Show Affiliations”]- National Laboratory for Magnetic Fusion, CIEMAT, Avda. Complutense 22, 28040 Madrid, Spain
- Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV-1063 Riga, Latvia
- Institute of Physics, University of Latvia, 32 Miera 32, LV-2169 Salaspils, Latvia
Abstract
Structural and elemental analyses of the RAFM steel (EUROFER 97) interface with flowing Pb–17Li eutectic (velocity 5 cm/s at 550 °C, 1000 h) under the action of a strong magnetic field (B = 1.7 T) were performed using optical microscopy, SEM, confocal microscopy, precision micro-hardness methods, SIMS and point or line-scan EDX analyses. The results show that the magnetic field induces a faster crushing of martensite into the grains, a deeper dissolution of grain boundaries, an enhancement of the Fe and Cr mass transfer and a fast detachment of corrosion layers due to MHD effects.
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