Speaker
Description
To improve the performance of plasma-facing components, various advanced concepts of W materials are being developed. In particular, tungsten-based refractory high-entropy alloys (HEAs) in the W–Ta–V–Cr–Ti system are attracting attention due to their excellent radiation resistance and strength at high temperatures. In this work, the intentional addition of boron to the W–Ta–V–Cr–Ti high-entropy alloy system is explored. Boron can significantly enhance plasma-facing performance by reducing sputtering, suppressing oxygen and other impurities, and lowering hydrogen recycling, while also promoting improved microstructural stability through boride formation.
The microstructure and properties of radiation-damaged samples of pure W and HEA alloys were compared. To simulate the damage morphology, 15 MeV W ion irradiation was conducted at the UK Dalton Cumbrian Facility at 700 °C. The microstructure investigations show that the BCC HEA phase was reinforced with TiC and TiB2-based precipitates formed during sample fabrication. Phase segregation under irradiation was examined using both grazing-incidence X-ray diffraction (GIXRD) and atom probe tomography (APT). The BCC phase was relatively stable, while the ceramic reinforcements showed significant irradiation-induced swelling. Minor formation of Cr clusters in the BCC HEA phase after irradiation was also detected using APT. Nanoindentation was used to investigate the irradiation hardening, showing an increase of 3-3.5 GPa and 1.5 GPa for the HEA and pure W, respectively. For plasma–material interaction studies, the damaged samples were exposed to deuterium plasma under two conditions: low-fluence/low-temperature irradiation at UKAEA and high-fluence/high-temperature irradiation at DIFFER. Deuterium retention and release behaviour were assessed using thermal desorption spectroscopy (TDS).