Simultaneous enhancement of hardness and wear and corrosion resistance of high‐entropy transition‐metal nitride

Binary transition‐metal nitrides (TMNs) are widely used as protective coating materials, and enhancing key performance characteristics are crucial to improving their robust and durable applications in harsh service environments. Compositional modulation via multiple elemental species offers an effective approach for optimizing physicochemical properties of TMNs, and establishing the composition–property relation is essential to the design of high‐performance TMNs. In this work, we report on a comparative study of our synthesized NbN, NbMoN, and (NbMoTaW)N films and examined their microstructure, mechanical properties, and tribological and corrosion behaviors. The high‐entropy (NbMoTaW)N film exhibits the highest hardness of 23.5 ± 1.35 GPa, which is ascribed to its high structural stability, increased elastic constant, and elastic modulus compared to the NbN and NbMoN films. The (NbMoTaW)N film also possesses the best wear resistance stemming from the highest H/E ratio and formation of self‐lubricating MoO3 and WO3 species; moreover, this film shows the best corrosion resistance attributed to the sluggish diffusion of Cl− due to lattice contraction and the structural stability caused by high‐entropy effect. This work demonstrates simultaneously enhanced hardness and wear and corrosion resistance in a high‐entropy TMN, opening a pathway for developing a new generation of advanced protective coating materials.