Effect of Ta addition on the fuzz formation of additively manufactured W based materials

As a divertor plasma-facing material, W will experience the high flux plasma irradiation. Especially, severe surface morphology change like fuzz formation can be induced by the He plasma irradiation. In this study, the fuzz formation on additively manufactured W and W-Ta was investigated. Rolled W, laser powder bed fused (LPBFed) W and W-Ta were exposed to high flux (~1023m-2s-1) He plasma in the linear plasma generator Magnum-PSI with ion energy 12-13 eV at 1273 K. The mean thickness of the fuzz at grain interiors of rolled W, LPBFed W and W-Ta was measured as 0.37 um, 0.71 um and 0.23 um, respectively. The fuzz suppression in LPBFed W-Ta can be attributed to the synergetic effect of solid-solution, dislocation, and secondary phase nanoparticles. Abnormally grown fuzz was observed near the pre-existing cracks of LPBFed W, while no such structure was found in LPBFed W-Ta. It is found that dislocations play a crucial role in inhibiting fuzz growth. This is confirmed by the difference of fuzz structure in rolled W and LPBFed W, where rolled W has a much greater dislocation density compare to LPBFed W. This work suggests that the fuzz growth kinetics may be tuned by tailoring the microstructures using the LPBF technique.