Alloying-Enabled Phase Selection and Twin-Mediated Plasticity for Ultrahigh Wear Resistance in Nanocrystalline FeCoNiTi Coatings

Achieving ultrahigh wear-resistance in structural coatings requires integrating high intrinsic strength with the ability to sustain plastic deformation. Here, we report a dual-phase nanocrystalline FeCoNiTi multiprincipal element alloy (MPEA) coating that attains a high yield strength of 3.3 GPa, a strain-hardening rate of 9.21 GPa, and an ultralow wear rate of 1.1 × 10–6 mm3/(N·m), surpassing most reported MPEA coatings. The coating is synthesized via rapid electrical-current-activated sintering, during which amorphized FeCoNiTi powders crystallize into a uniform fine-grained FCC matrix (∼32.5 nm) with ∼40 vol % ordered coherent L12 nanoprecipitates. Addition of Ti promotes compositional segregation and L12 phase formation, which facilitates twinning-induced plasticity and enhances strain hardening. The in situ formation of a TiO2 tribo-film also provides a lubrication effect. Furthermore, the twin-mediated deformation suppresses strain localization and grain boundary sliding. This work establishes a rapid and robust pathway for designing high-performance antiwear coatings through alloying-driven phase selection and defect engineering.