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 D 2 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 D 2 exposure at 300 °C. The total D retention after D 2 exposure at 600 °C was lower, but it was concentrated in the W/TiZr4Be/Ta seam, and the formation of an additional ZrFe 2 D 2.66 phase was observed.