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

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/m2. Surface observations show that the large-size blisters (~8-10 µm) and few small blisters (< 2 µm) are formed on the W samples. For WZC, the surface of samples is covered by high density of small blisters (< 1 µm), and no blister large than 2 µm is found. Cross-section views show that the large-size blisters originate from sub-surface 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 normal direction close to [111] for both types of samples. 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 are mainly retained in the near surface region of WZC and W. Besides, a higher and broaden D peak is observed at a depth between 0.1-0.25 µm in WZC, but the intensity and width of D peak is lower and thinner in W. The desorption spectra of WZC shift to 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/m2.