Evaluation of Tungsten Heavy Alloys and Tungsten Silicon Carbide based composites in DIII-D divertor

An experimental study was performed to evaluate advanced tungsten-based materials including tungsten heavy alloys (WHAs), tungsten fiber silicon carbide fiber-reinforced composites (W_fSiC_f/W), and functionally graded tungsten-silicon carbide (FG-W/SiC) exposed to reactor-relevant heat loads in the DIII-D divertor. Post-exposure SEM/EDS analysis revealed that angled WHA samples showed localized edge melting and surface damage with tungsten granulation, while flat WHA samples exhibited only mild erosion and deposition halos of Ni, Fe, and Cu. W_fSiC_f/W and FG-W/SiC samples (annealed and non-annealed) demonstrated strong thermal resilience, with minimal erosion under heat fluxes of ~2-6 MW/m². Conducted under the Fusion Pilot Plant (FPP) Candidate Materials Thrust, this study aims to raise the technology readiness level (TRL) of next-generation plasma-facing materials. Small samples (ø6 mm, flat and 10° angled) of WHA (W-Ni-Fe and W-Ni-Cu), W_fSiC_f/W, and FG-W/SiC were exposed in the lower divertor near the outer strike point (OSP) in H-mode plasmas with ~40 Hz ELMs using the Divertor Material Evaluation System (DiMES). A new OSP sweeping technique was used to distribute the heat flux uniformly, enabling controlled comparisons across material samples. In-situ filtered imaging and spectroscopy further quantified the erosion behavior. These findings validate the robustness of these novel materials under fusion-relevant conditions and support their continued evaluation.