DIFFER
DIFFER Publication

Delayed surface degradation in W-Ta alloys at 400° C under high-fluence 40 eV He plasma exposure

Author
Abstract

The surface modifications in W-xTa alloys (x = 0, 6, 11 wt.%), as potential material candidates for tokamak components facing the fusion plasma, have been assessed at a temperature of ∼400 °C, by exposing the material surface to 40 eV He for increasing He fluences up to 10 27 m−2 and flux of ∼10 23 m−2 s−1. Surface wave-like structures appear in all samples at a fluence of ∼10 26 m−2, whereas at the higher fluence of ∼10 27 m−2 the material's surface is characterised by the presence of blisters and ablations. This suggests a new critical fluence for blistering in pure He plasma to be between 10 26 and 10 27 m−2. There is also a near-surface layer with a thickness of ∼200 nm that contains He bubbles of 2.20–2.70 nm in average size. Increasing Ta content leads to a small reduction in bubble size, and to clear reductions in the presence of blisters and ablations. Ta alloying can improve the hardness and yield strength and reduce the He diffusivity in the material. This therefore delays bubble formation and surface blistering and ablations that are affected by these mechanical properties. This was exemplified at the highest fluence by a large mitigation of surface material ablation.

Year of Publication
2023
Journal
Fusion Engineering and Design
Volume
197
Number of Pages
114061
Date Published
12/2023
DOI
10.1016/j.fusengdes.2023.114061
PId
f5b0ca78a177737aa325ffaa1a15a3c3
Alternate Journal
Fusion Eng. Des.
Label
OA
Journal Article
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