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

Abstract

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.