Potential substitution of superalloys with high-entropy alloys: A study on erosion of Al0.5CrFe1.5NixTi0.2 in comparison with Inconel 625

Ni-based superalloys such as Inconel 625 are widely used in ambient and high-temperature environments due to their excellent strength and thermal stability; however, their resistance to solid-particle erosion remains limited. In this work, a series of Al₀.₅CrFe₁.₅NiₓTi₀.₂ high-entropy alloys (HEAs) with varying Ni content were systematically investigated as potential alternatives to Inconel 625 for erosion-prone applications across a wide temperature range. The mechanical properties were evaluated through compression and macro-hardness testing, while detailed microstructural characterization was performed using electron microscopy. Increasing Ni content was found to promote the formation of a ductile FCC phase at the expense of harder BCC phases, enabling tunable strength–toughness combinations. Solid-particle erosion resistances at a representative impingement angle of 45° respectively at room temperature, 500 °C, 700 °C, and 1000 °C were assessed. All HEAs under study exhibited significantly superior erosion resistance compared to Inconel 625 at all tested temperatures. Post-erosion surface analyses reveal that the enhanced erosion resistance is further supported by the formation of protective oxide scales. However, higher Ni contents reduced the contribution of Al- and Cr-rich oxides to the overall scale composition, diminishing the effectiveness of the protective films. The obtained results demonstrate that compositionally tailored HEAs can simultaneously achieve superior erosion resistance and mechanical performance, offering a promising pathway for replacing conventional Ni-based superalloys in erosion-critical, high-temperature applications. • Ni promoted the formation of FCC phase while demoted harder BCC phases in high-entropy Al0.5CrFe1.5NixTi0.2, helping balancing its desirable plasticity and hardness. • The erosion behaviours of the high-entropy alloy (HEA) at room and elevated temperatures were evaluated. • The HEA performed considerably better than Inconel 625, and can be a highly competitive alternative for Ni-based superallys. • The oxide film on the Al0.5CrFe1.5NixTi0.2 alloy was more protective than that on the superalloy, against oxidation and oxidative erosion.