Exceptional high-temperature corrosion resistance of multi-component alloys via modulating Al and Nb

The chemical compatibility of metallic materials with thermal transfer/storage media, which often involves aggressive working conditions (i.e., high-temperature, corrosive environments), challenges the safe operations of advanced and sustainable energy-related infrastructures. Here, we report the corrosion-oxidation behaviors of three multi-component alloys (MCAs) when exposed to a corrosive heavy-liquid metal condition (i.e., molten Pb at 650 ℃ with 10−6 wt% oxygen dissolved). The two compositions, Al0.36Cr0.67FeNi0.98 (HAl11) and Al0.27Cr0.71FeNi1.16Nb0.17 (HAl8Nb), show excellent corrosion-resistance via passivating a protective oxide scale on the alloy surface. Further characterizations of the oxide layers differentiate their corrosion-oxidation mechanisms: a protective Al2O3 oxide layer (with Cr and Fe segregation outmost) formed on HAl11 and a duplex oxide layer (outward growth of FeCr2O4/Cr2O3 layer plus inward growth of an Al2O3 layer) with internal oxidation on HAl8Nb. Adding Nb improved the corrosion-oxidation resistance (“Nb-doping effect”) by enhancing the outward diffusion of metallic elements and promoting the rapid establishment of an alumina scale. ... mehrBesides, the presence of AlNbO4, which was predicted by thermodynamics calculation, lying between the spinel and Al2O3 formation, was also confirmed by experimental observations. Our findings advance the mechanistic understanding of MCAs’ performances in extreme conditions and provide novel strategies for designing corrosion-resistant alloys targeting aggressive application environments.