Thermal Fatigue Tests of Vacuum Plasma-Sprayed Tungsten Tiles for Plasma-Facing Material

Tungsten coating as a plasma-facing material on copper alloys is an important issue of a tokamak fusion device. Tungsten tile was created by means of plasma-spraying technology. The properties of the tungsten coating are as follows: low porosity of 4.7%, [approximately]92% of the theoretical tungsten bulk density, and high thermal conductivity of [approximately]79.7 W/mK, which are interesting properties for the plasma-facing material. To alleviate the stress concentration, the tile was designed with rounded edges with a radius of 5 mm. The fatigue performance of the tungsten tile was tested at 5 MW/m² in an electron beam facility. No damage was observed after 38 cycles at 250 s per cycle. It is concluded that the rounded-edge design is helpful in reducing the maximum stress and in improving the resistant heat load property, which was proved by finite element analysis.