The Characteristics of Light (TiCrAl_0.5NbCu)C_xN_y High-Entropy Coatings Deposited Using a HiPIMS/DCMS Technique

Abstract

Multi-component high-entropy (TiCrAl0.5NbCu)CxNy coatings targeting applications requiring medium-to-high friction and wear-resistant surfaces were fabricated through the co-sputtering of elemental targets in an Ar + CH4 + N2 reactive atmosphere using a hybrid HiPIMS/DCMS technique. Two sets of samples were fabricated: (a) (TiCrAl0.5NbCu)Cx high-entropy carbides (HEC) and (b) (TiCrAl0.5NbCu)CxN0.13 high-entropy carbonitrides (HECN), 0 ≤ x ≤ 0.48. The structural, mechanical, tribological, and corrosion resistance properties were thoroughly investigated. The metallic sample exhibits a single BCC structure that changes to FCC via an intermediary amorphous phase through the addition of C or N to the content of the films. The crystallinity of the FCC phases is enhanced and the density of the films decreases down to 5.5 g/cm3 through increasing the carbon fraction up to 48%. The highest hardness of about 16.9 GPa and the lowest wear rate of about 5.5 × 10−6 mm3/Nm are presented by the samples with the largest carbon content, x = 0.48. We found a very good agreement between the evolution of H/E and H3/E2 parameters with carbon content and the tribological behavior of the coatings. The best corrosion resistance was presented by the low-carbon carbonitride samples, showing a charge transfer resistivity of about 3 × 108 Ω∙cm, which is more than three times larger than that of the metallic HEA. The best tribological characteristics for envisioned application were presented by (TiCrAl0.5NbCu)C0.3N0.13, showing a coefficient of friction of 0.43 and a wear rate of about 7.7 × 10−6 mm3/Nm.

Keywords

• high-entropy alloys
• structure
• surface morphology
• mechanical properties
• electrochemical properties