Improvement of the mechanical and the tribological properties of CrNbTiMoZr coatings through the incorporation of carbon and the adjustment of the substrate bias voltage

Abstract

High-entropy alloy (HEA) coatings exhibit high hardness and high strength and have attracted wide attention. The improvement in the tribological performance , such as low friction coefficient and wear rate, is a longstanding challenge and is critical in the broad application of HEA coatings. In this study, a series of CrNbTiMoZr coatings was synthesized using the direct current magnetron sputtering by tuning substrate bias voltages. A continuous transformation in the structure from the amorphous phase to the face-centered cubic phase was observed in HEA carbide coatings. The residual stress and the hardness monotonously increased with the substrate bias voltage. The addition of carbon reduced the friction coefficient and the wear rate of HEA coatings. Consequently, we achieved a HEA carbide coating at −200 V combined with high hardness (17.4 GPa), low friction coefficient (0.3–0.4), and low wear rate (1.18 × 10 −6 mm 3 ·N −1 ·m −1 ). This study provides a new guidance for designing new HEA coatings with high strength and low wear. • The high-entropy alloy coatings were synthesized by DC magnetron sputtering. • The addition of carbon in HEA coatings effectively improved tribological properties. • The maximum hardness of the carbide coating about 17.4 GPa was reached at −200 V.