Surface blistering and deuterium retention behaviors in pure and ZrC-doped tungsten exposed to deuterium plasma

Abstract

Surface blistering and deuterium (D) retention behaviors in pure tungsten (W) and 0.5 wt% ZrC-doped W alloy (WZC) exposed to D plasma have been investigated as a function of incident D fluence up to 2.6 × 1025 D m−2. Surface observations show that large-sized blisters (∼8–10 μm) and a few small blisters (<2 μm) are formed on the W samples. For WZC, the surface of the samples is covered by a high density of small blisters (<1 μm), and no blister larger than 2 μm is found. Cross section views show that the large-sized blisters originate from subsurface grain boundaries, and the small blisters originate from intra-granular cavities at depths much closer to the surface. The intra-granular blisters are preferentially formed on the grains with a normal direction close to [111] for both types of sample. The inter-granular blisters formed in pure W are significantly suppressed in WZC, and the fluence threshold for blister formation in WZC is lower than that in W. The D depth distributions indicate that the implanted D is mainly retained in the near-surface region of WZC and W. Besides, a higher and broader D peak is observed at a depth of between 0.1–0.25 μm in WZC, but the intensity and width of the D peak is lower and thinner in W. The desorption spectra of WZC shift to the lower temperature side as compared to W, and the total retained D amount in WZC and W is comparable in the fluence range of 2.8 × 1024–2.6 × 1025 D m−2.