Spark plasma sintered tungsten – mechanical properties, irradiation effects and thermal shock performance

Abstract

Tungsten-based materials are the most prospective candidates for the plasma facing components for future fusion devices, such as DEMO. In order to improve their properties, various modifications are being developed, including composites, alloys, and different processing routes. Spark plasma sintering (SPS) is among the prospective preparation technologies; thanks to the relatively low temperatures and short processing times, it enables the preservation of fine grain structure, beneficial for radiation resistance. In a previous study, SPS W has shown promising mechanical properties at moderate temperatures, however, the irradiation effects were yet to be investigated.Fine-grained W was prepared by spark plasma sintering. Together with other W-based materials, the samples were neutron-irradiated at the BR2 reactor at 600 and 1000 °C up to 0.24 and 0.7 dpa, respectively. Mechanical testing - including tensile test and fracture toughness tests - was performed in irradiated and un-irradiated states in the 200–600 °C temperature range. Fractographic observations were performed to help in understanding the impact of the irradiation effects on the fracture mechanism. For the SPS W, a shift of DBTT from ~300 °C to ~600 °C due to irradiation was observed. High heat flux testing was carried out in repeated thermal shock mode at the PSI-2 device at room temperature, 400 and 1000 °C and fluxes up to 1.6 GW/m2. The results showed rather promising resistance to cracking under these conditions. In these tests, the SPS tungsten showed comparable or better performance than reference, ITER-qualified tungsten material.