Smart alloys as armor material for DEMO: Overview of properties and joining to structural materials

Tungsten test is currently the baseline first-wall armor material for a future DEMOnstration power plant. Smart alloys, containing tungsten (W), 11.4 weight (wt) % chromium (Cr), and 0.6 wt% yttrium (Y), aim at achieving passive safety in case of air ingress into the vacuum vessel and a loss-of-coolant accident causing a temperature rise above 1200 K for weeks. In such a case, smart alloys suppress oxidation and sublimation of radioactive W. This publication summarizes several important properties of smart alloys: the suppression of oxidation, the hardness as a function of the microstructure, and potential carbide formation in the presence of carbon (C) impurities. Further, first results on joining them to the EUROFER by field-assisted sintering technology (FAST) without interface layer are presented. In literature, FAST is also known as spark plasma sintering (SPS). A stable joint with an tungsten-iron (W-Fe) diffusion layer of 100 nm at the interface was achieved. The joint survived several heat cycles to 873 K.

Automated summary

This article highlights the importance of tungsten alloy as the baseline first-wall armor material for a future DEMOnstration power plant and discusses its performance in terms of safety, oxidation suppression, and hardness. Moreover, initial success in joining smart alloys to EUROFER using FAST technology is presented.