Surface modification of W-V alloy exposed to high heat flux helium neutral beams

Surface modification of tungsten vanadium (W-V) alloy under high heat flux helium particle bombardment has been studied. W-5 wt.% V samples were irradiated by repeated helium pulses at a peak surface temperature of 900 °C and 1800 °C, respectively, in the neutral beam facility GLADIS. The effect of helium fluence on the surface morphology changes was investigated by increasing the helium fluence from 1 × 10²² m^-2- 2 × 10²² m^-2. Blistering is the typical structure after the repeated helium pulses loading at 900 °C, and it becomes more severe with increased fluence. A porous structure becomes dominant at 1800 °C. An evolution of a porous structure to coral-like structure is observed as fluence increases. In addition, the three typical regions in the W-5V, W-enriched region, W-V solid solute region, and V-enriched region, exhibit different damage features. The W-V solid solute region shows better surface damage resistance compared to the other two regions.