Investigation of microstructure and deuterium retention in the reduced activation tungsten-steel brazed joint

The combination of reduced-activation ferritic-martensitic steels (RAFM) and tungsten is suggested for plasma-facing components in future fusion reactors, but joining these materials is challenging. One promising method is a brazing technique that uses a Ta interlayer and a fully reduced activation brazing alloy, TiZr4Be. The initial microstructure of the Rusfer/TiZr4Be/Ta/TiZr4Be/W joint and transformations caused by exposure to D2 gas at elevated temperatures and a pressure of 1 Pa were assessed using electron backscatter diffraction (EBSD), synchrotron X-ray diffraction analysis and secondary ion mass spectrometry. The joining layer was the main center of deuterium accumulation, but there were no changes in the microstructure after D2 exposure at 300 degrees C. The total D retention after D2 exposure at 600 degrees C was lower, but it was concentrated in the W/TiZr4Be/Ta seam, and the formation of an additional ZrFe2D2.66 phase was observed.