Effects of CH4 flow ratio on the structure and properties of reactively sputtered (CrNbSiTiZr)Cx coatings

High-entropy (CrNbSiTiZr)Cx coatings were successfully fabricated by reactive radio-frequency magnetron sputtering using an equimolar CrNbSiTiZr alloy target under CH4-containing Ar flow. The effect of the CH4 flow ratio on the chemical composition, microstructure, mechanical and tribological properties of (CrNbSiTiZr)Cx coatings was investigated. The carbon content in the coatings varied from 36.7 at% to 87.8 at% with an increasing CH4 flow ratio from 3% to 20%. The (CrNbSiTiZr)Cx coatings revealed a simple NaCl-type FCC (face-centered cubic) structure. The maximum hardness of 32 GPa was obtained at the carbon content of 36.7 at% by applying substrate bias of −100 V. On the other hand, the coating with high carbon content of 87.8 at% possessed superior wear resistance, which friction coefficient and wear rate were, respectively, 0.07 and 2.0 × 10−7 mm3/N·m.