Hydrogen Retention in Dispersion Strengthened Tungsten Alloys

Tungsten (W) is a leading candidate as a plasma-facing component (PFC) for the divertor of fusion tokamak reactors. Dispersion strengthening with transition metal carbides (e.g., TiC, TaC, ZrC) is a promising method to improve the thermomechanical stability of W. Dispersion strengthened tungsten (DSW) alloys have demonstrated enhanced recrystallization temperatures and thermal shock resistance compared to W. Despite the thermomechanical benefits, further investigation is needed into the trapping and release mechanisms of dispersion phases on hydrogenic plasma species. DSW samples containing 1 wt% TiC, ZrC, or TaC, along with commercial W controls were exposed to an RF plasma discharge of 150 eV D₂⁺ to a 10²⁵ m^-2 fluence. In-situ low-energy ion scattering (LEISS) and x-ray photoelectron spectroscopy (XPS) were employed to explore surface chemical effects during D₂ gas dosing. XPS and LEISS confirmed that dispersoids were present as transition metal oxides. Thermal desorption spectroscopy to 900 °C revealed a desorbed D flux in DSW by up to a factor of five higher than recrystallized W. The main desorption peak in DSW samples was shifted to a higher temperature (~500 °C) than commercial W (~400 °C). Among DSW samples, W-TiC had the highest desorbed D flux, followed by W-TaC and W-ZrC.