(AlCrSiTiVZr)Nx high-entropy alloy nitride coatings: Enhanced hardness and damage-tolerance through nanocomposite structure

Ultra-hard (AlCrSiTiVZr)N_x high-entropy alloy (HEA) nitride coatings were deposited using co-filter cathodic vacuum arc (FCVA) deposition technique under N₂ gas flow rates (F_N) of 0, 20, 40, 60 and 80 sccm. The repercussion of F_N on the phase structure, texture, element constitution, mechanical properties and tribological property of the coatings were researched. The N content in the HEA nitride coatings saturates at ∼50 at% when F_N = 40 sccm, and remains nearly unchanged with further increase in F_N. The phase structure of the HEA nitride coatings transforms from the amorphous structure to a nanocomposite structure with simple face-centered cubic phase structure embedded in the amorphous matrix as nitrogen element was doped. The hardness of the nitride coatings increases with increasing F_N, and reaches a maximum of 50.16 GPa at F_N = 80 sccm. The ultra-hardness of the (AlCrSiTiVZr)N coatings is mainly due to the joint effect of the formation of Me-N bonds and the amorphous/nanocrystalline composite structure, severe lattice distortion and ion beam assisted bombardment strengthening. In addition, the ultra-hard (AlCrSiTiVZr)N_x high-entropy alloy nitride coatings present excellent wear resistant, which can be chosen as protective coatings deposited on the surface of the engineering components.