Mechanical, Tribological, and Anti-corrosion Properties of Nitrogen-Doped AlCrNbSiTiMoW High-Entropy Coatings

(AlCrNbSiTiMoW)N high-entropy alloy (HEA) coatings with various nitrogen-to-argon gas flow ratios ( R N = N 2 /Ar) in the range of R N0 to R N1.25 were deposited on WC and Si substrates using a radio-frequency magnetron sputtering system. The as-sputtered coatings were then annealed at 950 °C for 1 hour in a vacuum. The effects of the nitrogen flow ratio on the composition, microstructure, mechanical properties, tribological properties, and corrosion resistance of the various coatings were systematically explored. The as-deposited R N0 , R N1.0 , and R N1.25 coatings exhibited FCC structures, while the R N0.5 and R N0.75 coatings had amorphous structures. Following the annealing process, all of the coatings showed an FCC structure. The annealing process had no significant effect on the hardness of the coatings. Thus, they were inferred to have excellent thermal stability. Among the coatings, the HR N1.0 coating showed the highest hardness (37.4 GPa), adhesion strength, and tribological properties, with a wear depth and wear rate of 0.07 μ m and 0.41 × 10 -6 mm 3 /Nm, respectively. The wear depth and wear rate of the HWC substrate were 0.28 μ m and 1.67 × 10 -6 mm 3 /Nm, respectively. Thus, compared with the HWC substrate, the HR N1.0 coating improved the wear depth and wear rate by 75.0 and 75.4%, respectively. The tribological performance of the annealed HR N1.0 coating was enhanced as a result of the formation of a greater amount of MoO 3 and WO 3 solid lubricant phases and a higher hardness and hardness-to-elastic modulus ratio. The R N1.0 coating exhibited the best corrosion resistance among all the coatings. The corrosion current density of the R N1.0 coating was 1.8 × 10 -7 A/cm 2 , while that of the WC substrate was 2.2 × 10 -7 A/cm 2 . In other words, the R N1.0 coating improved the corrosion resistance by 18.1%. However, the corrosion resistance reduced following the annealing process due to a greater surface roughness.