Joining of tungsten with low-activation ferritic-martensitic steel and vanadium alloys for demo reactor

The conceptual designs of the blanket and the helium-cooled divertor of the DEMO reactor require joining of reduced activation steel (for example RUSFER EK-181, EUROFER, etc.) and tungsten. Significant differences in their physical properties can lead to the generation of the stresses during cooling and, as a result, to the failure of the joint. In this paper, diffusion brazing of RUSFER EK-181 steel with tungsten using a V-4Ti-4Cr interlayer was obtained. Rapidly-quenched ribbon brazing alloys based on copper of various compositions were used. Brazing was carried out in vacuum furnaces at temperatures in the range of 800-1000 °C. The structural-phase states of the joints obtained were studied, the microhardness was measured, and thermocycling tests were performed in the interval of 700 to 25 °C. FEM simulation was used to calculate the optimal thickness of the interlayer.