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 degrees 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 degrees C. FEM simulation was used to calculate the optimal thickness of the interlayer.