Achieving super wear resistance in additively manufactured eutectic high-entropy alloys via self-hardening design at intermediate temperatures

Interfacial degradation, oxidative damage, and fatigue cracking pose persistent challenges to structural alloys operating in the intermediate-temperature regime (400–600 °C), often resulting in accelerated wear and premature failure. To address this, we design a multicomponent Ti-containing eutectic high-entropy alloy (EHEA) via additive manufacturing (AM) and targeted Ti alloying to engineer a thermally stable, refined microstructure tailored for enhanced tribological performance. The resulting alloy achieves an ultralow wear rate of 6.20 × 10⁻⁵ mm³/N·m at 600 °C—approximately 86% lower than that of conventional Ni-based superalloys. Microstructural analyses reveal that rapid AM solidification produces ultrafine equiaxed grains with > 90% high-angle grain boundaries, stabilized by Ni segregation and contributing to robust Hall–Petch strengthening. Ti addition not only stabilizes the B2 phase (~ 87 vol%) but also promotes the selective formation of dense Al₂O₃/Cr₂O₃ oxide scales, which suppress oxidative wear. Further friction triggers the in-situ formation of Ni-rich hexagonal close-packed (HCP) nanoprecipitates, which accommodate strain and provide in-situ self-hardening. The multi-structural system enables the alloy to overcome the temperature–wear trade-off typically observed in conventional HEAs at intermediate temperatures. This study establishes a new alloy design strategy that integrates AM-enabled grain boundary engineering with element-specific oxidation control to realize wear-resistant structural materials for intermediate-temperature applications.