Effect of Substrate Bias on the Structure and Tribological Performance of (AlTiVCrNb)CxNy Coatings Deposited via Graphite Co-Sputtering

In the existing literature, there are few studies on the effect of deposition bias on the tribological properties of carbon-doped high-entropy alloy coatings. In order to further study the effect of the deposition bias on the properties of coatings, (AlTiVCrNb)CxNy coatings were deposited via unbalanced RF magnetron sputtering. The microstructure and tribological properties of carbon-doped high-entropy alloy ceramic coatings under different deposition biases were studied. The composition, morphology, crystal structure, and chemical morphology of each element of the coating were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The hardness, elastic modulus, friction, and wear properties of the coating were further characterized using a nanoindentation instrument, reciprocating sliding friction, a wear tester, and a white light interferometer. The coating density reached the optimal level when the deposition bias value was 90 V. The hardness and elastic modulus of the (AlTiVCrNb)CxNy coating increased first and then decreased with an increase in deposition bias, and the maximum hardness was 23.98 GPa. When the deposition bias was 90 V, the coating formed a good-quality carbon transfer film on the surface of the counterbody due to sp2 clusters during the friction and wear process. The average friction coefficient and wear rate of the (AlTiVCrNb)CxNy coating were the lowest, 0.185 and 1.6 × 10−7 mm3/N·m, respectively. The microstructure, mechanical properties, and tribological performance of the (AlTiVCrNb)CxNy coating were greatly affected by the change in deposition bias, and an (AlTiVCrNb)CxNy coating with excellent structure and friction properties could be prepared using graphite co-sputtering.