High hardness improves the material’s load-bearing capacity, resulting in the enhancement of tribological properties. However, the high hardness is difficult to achieve for TiAlN coating due to the transformation of the close-packed structure from cubic to hexagonal and the increase in the grain size when the Al content is high. In the present study, the ultrahard TiAlN coatings (hardness > 40 GPa) are successfully developed by filtered cathodic vacuum arc technology to study the effect of nitrogen flux rate on tribological behaviors. The highest hardness of 46.39 GPa is obtained by tuning the nitrogen flux rate to achieve the regulation of Al content and the formation of nanocrystalline. The stable fcc TiAlN phase is formed via the solid-phase reaction under a high nitrogen concentration, and more aluminum atoms replace the titanium atoms in the (Ti, Al)N solid solution. The high Al content of the Ti_0.35Al_0.65N coating has a nanocrystalline structure and the average crystalline size is 16.52 nm. The TiAlN coating deposited at a nitrogen flux rate of 60 sccm exhibits the best properties of a combination of microhardness = 2972.91 Hv_0.5, H = 46.39 GPa, E = 499.4 Gpa, ratio H/E* = 0.093 and ratio H³/E*² = 0.403. Meanwhile, the TiAlN coating deposited at 60 sccm shows the lowest average friction coefficient of 0.43 and wear rate of 1.3 × 10⁻⁷ mm³ N⁻¹ m⁻¹ due to the best mechanical properties.

To improve the anti-tribocorrosion property, and decrease the metal dissolution and wear of stainless-steel components caused by the synergistic action of corrosion and friction in marine environments, Ti-DLC coatings were obtained on steel substrate using a filtered cathodic vacuum arc (FCVA) system by adjusting bias voltage. The structure, mechanical properties, corrosion, and tribocorrosion behavior were investigated. Increasing the bias voltage from −50 V to −300 V, Ti content decreased from 23.9 to 22.5 at.%, and grain size decreased first, and then increased. Obvious TiC grains embedded in the amorphous carbon matrix were observed in the coating from the TEM result. Hardness increased from 30.23 GPa to 34.24 GPa with an increase in bias voltage from −50 to −200 V. The results of tribocorrosion testing showed that the Ti-DLC coatings at −200 V presented the best anti-tribocorrosion performance with the smallest friction coefficient of 0.052, wear rate of 2.48 × 10⁻⁷ mm³/N∙m, and high open-circuit potential, which is mainly due to the dense structure, high value of H/E* and H³/E*², and great corrosion resistance. Obtained results suggest that the Ti-DLC coating with nanocomposite structure is a potential protective material for marine equipment.