Thermo-Mechanical and Thermal Shock Characterization of Potassium Doped Tungsten

The increasing importance of W and W-alloys as plasma facing materials (PFM) for future nuclear fusion facilities (ITER, DEMO) requires an increasing understanding of the materials behavior under operational loading conditions. This comprises the microstructural response at high temperature (recrystallization behavior, thermal shock and fatigue resistance). The latter are strongly correlated to its thermo-mechanical and thermo-physical characteristics. One potential PFM candidate is potassium-doped-tungsten WVMW (PLANSEE-AG). It is qualified in its as-received and recrystallized state (Tann=1800°C) and is compared with a standard W-rod. One qualification criteria is the crack formation under fusion relevant short transient events (disruptions, ELMs). This is addressed by single and multiple thermal shock loading in the electron-beam facility JUDITH at different power densities and base temperatures with subsequent microstructural and metallographic studies of the material damage. Annealed WVMW is showing the best performance with the lowest crack formation transition temperature (150-200°C). For a better understanding of the cracking process and the establishment of a FEM-database, tensile tests are performed up to 2000°C (upper limit operation temperature during steady-state heat loading). The tests are performed at different speed (0.2 and 42mm/min) to address the fast deformation processes during thermal shock, showing a high ductility of the annealed material.