Friction-driven surface segregation of (AlCrZrMoV-Ti-B-C)N_x crystal–amorphous nanocomposites enables wear reduction

High-entropy ceramic films offer superior hardness over conventional metallic films, but their inherent brittleness greatly restricts wider applications. Crystalline–amorphous nanocomposites demonstrate greater strength, improved toughness, and the ability of uniform deformation. In this study, a nanocomposite structured film with fine (AlCrZrMoV)N ceramic grains (2–8 nm) embedded in a C-based amorphous matrix was designed based on the thermodynamic principles and prepared by magnetron co-sputtering. The nano-composite film exhibits higher hardness, with a wear volume under dry sliding condition that is two orders of magnitude lower than that of the corresponding high-entropy alloy. The enhanced hardness and elastic recovery are key factors for its superior wear resistance. The crystalline–amorphous dual-phase structure retards cracking and brittle damage through restricting plastic flow by the amorphous phase. Friction induces the break of C–metal (Me) bond, activating the diffusion of free carbon in the subsurface layer to form graphite-like (sp² amorphous carbon) friction film, which acts as a dissipative medium for the contact stresses, thus preventing further wear of the interacting surfaces. This study provides new insight into the design of wear-resistant materials and highlights the significant roles of crystal–amorphous nano-heterostructure structure in improving the tribological properties. Through precisely designing the microstructure of nanocomposites, deformation layers with specific structures and properties are achieved via friction-induced microstructural evolution.