A multi-target co-deposition magnetron sputtering system was employed to prepare two sets of AlCrTiZr-based high-entropy nitride coatings in term of (AlCrTiZrNi)N_x and (AlCrTiZrMo_x)N. The chemical composition, microstructure, mechanical and tribological properties of the coatings were studied systematically. For (AlCrTiZrNi)N_x coatings with varying N content, the results show that with N₂ flow rates from 0 to 16 sccm, the nitrogen content increases to 55.7 at.% and the phase structure changes from amorphous to FCC. The hardness increases obviously with the increase of nitrogen content. When the nitrogen flow rate is 12 sccm, the coating has the highest hardness of 31.77 GPa and the lowest wear rate of 1.23×10^-5 mm³/(N·m). The wear resistance results show that all the hardness and toughness contribute to the coatings wear resistance. For (AlCrTiZrMox)N coatings with varying Mo content, the results reveal that the Mo content significantly affects the microstructure, hardness, toughness, and tribological behavior of the coatings. With the addition of Mo, the crystallinity increases and the preferred orientation of the coating changes from (111) to (200). Hard yet tough high-entropy ceramics coatings (TiZrAlCrMo_x)N can be obtained with a hardness of 30.24 GPa, and good toughness (no obvious cracks). The coatings with Mo show excellent tribological properties compared to those without Mo: the friction coefficient reduces to 1/3 (from 0.72 to 0.26) and the wear rate reduces to 1/10 (from 3.39×10^-5 mm³/(N·m) to 3.15×10^-5 mm³/(N·m)). The low friction coefficient results from the formation of layered MoO₂ which reduces the shear force, and the low wear rate results from both the high hardness and toughness.
 

High-entropy nitride coatings, Magnetron sputtering, Mechanical properties, Tribological properties