Corrosion behavior of Zr35Ti30Nb20Al10Ta5 refractory high entropy alloy after 400 days testing in 360°C water and 400°C steam

High-entropy alloys have great potential as candidate structural materials in nuclear reactors. However, current studies lack the assessment of the long-time corrosion performance of materials in service environments. In this paper, the corrosion behaviors of Zr35Ti30Nb20Al10Ta5 refractory high-entropy alloy (RHEA) immersed in 360 degrees C/18.6 MPa water and 400 degrees C/10.3 MPa steam for up to 400 days were investigated. The RHEA exhibited a faster early corrosion weight gain and slower late weight gain in both environments. The oxidation kinetic curves showed a near parabolic law. The RHEA formed a single oxide film with a thickness of -3.5 mu m in the 360 degrees C water. In contrast, the oxide film in steam environment was a -10.1 mu m bilayer structure. The oxide film in both environments were consisted of multiple oxides. A diffusion layer of Zr and Al depletion was present under the oxide film. The composition of the outer oxide layer in the steam environment was similar to that of the single oxide film in the 360 degrees C water. While the inner oxide film was mainly composed of oxides of Nb, Ta and Ti elements. The oxide film surface in the 360 degrees C water formed an AlO(OH) boehmite phase, which was shed during corrosion process. In the steam environment, the outer oxide layer surface retained the boehmite phase, gradually transforming into Al2O3 after long-time corrosion.