Comparative studies of pure W, WK, and W-Y2O3 applied on the flat-tile W/Cu divertor mock-up: A combined experimental and FEM-based numerical investigation on the high heat loading performance

Abstract

Tungsten, as the selected plasma-facing material in ITER, attracts the most attention in divertor material design of the current Tokamak device. However, severe cracks of pure tungsten are widely found in experiments of the present tokamaks and high heat flux facilities. Advanced tungsten alloys (potassium-doped tungsten, WK, and yttria-dispersed tungsten, W-Y₂O₃) have been greatly improved after years, with a significantly higher strength, higher toughness, higher recrystallization temperature, and lower ductile-brittle transition temperature. As a result, it is expected to improve the divertor's high heat loading performance with advanced alloys. However, few divertor components made from these advanced alloys have been tested and therefore in this study, a flat-tile W/Cu divertor mock-up with 6 tiles of 5 mm thick swaged or rolled pure W, WK, W-Y₂O₃, was tested by the electron-beam facility (EMS-60) under 20 MW/m² heat flux. The recrystallization depth was 1–2 mm for pure tungsten, while no recrystallization was found in WK and W-Y₂O₃. This high heat flux test result shows a significant advantage in recrystallization for WK and W-Y₂O₃ under adverse test conditions, which can increase confidence in their use in current and future divertor component designs.