Surface modification of ZrC dispersion-strengthened W under low energy He plasma irradiation

Abstract

ZrC dispersion-strengthened W exhibits high strength/ductility, low ductile-to-brittle transition temperature, and excellent thermal shock resistance, making it a promising candidate plasma-facing material for future fusion devices. In this study, surface modification of 0.5 wt.% ZrC dispersion-strengthened W (WZrC) under low energy and high fluence He plasma irradiation at high temperature was presented. Under the energy of 90 eV and fluence ranging from 6 × 1024 He∙m-2 to 2 × 1026 He∙m-2 He irradiation at 920 ℃, typical fuzz nanostructure appeared on the W matrix of WZrC. The fuzz showed comparable thickness and structure features to pure W, which indicates limited effects of the particle’s addition on resistance to high fluence He irradiation at high temperatures. Besides, the erosion behavior of particles under He plasma irradiation has been investigated, which is thought to be dominated by a sputtering process. Under the He influence of 6 × 1024 He∙m-2, only nanopores were observed in the surface region. With fluence increasing to 5 × 1025 He∙m-2, the surface became relatively uneven with larger holes and stalagmitic structures. And W accumulated on the top of stalagmitic structures due to the subthreshold sputtering under He irradiation. When fluence further increased to 2 × 1026 He∙m-2, the particles were eroded completely and covered by the extended fuzz, forming cavities. In addition, distinctive layered nanotendrils were observed above the cavities, which were characterized to be consist of inner W-riched skeletons and outer Zr-riched layers. It indicates that the layered nanotendrils should be the result of fuzz extension combined with particles sputtering and redeposition.