Design and tribological performance of CrN/Mo2N/MoSx composite coating in wide temperature range inspired by oxidation kinetics principle

Inspired by oxidation kinetics principle, a series of CrN/Mo2N/MoSx composite coatings with different compo-sitions were prepared by magnetron sputtering technology. Microstructure, chemical composition and me-chanical were systematically investigated. The friction and wear behaviors of the CrN/Mo2N/MoSx coatings sliding against Al2O3 ceramic ball at 25-750 degrees C were also evaluated by a ball-on-disc tester (load: 2 N, frequency: 5 Hz, sliding distance: 5 mm). X-ray diffraction, transmission electron microscope and Raman spectroscopy were used to thoroughly analyzed for wear tracks at different temperatures to reveal the mechanism of low wear of the composite coating. Results showed that all of the coatings exhibit polycrystalline structures and the morphol-ogies grow in an obvious columnar crystal. The CrN/Mo2N/MoSx composite coating presented a wear rate as low as 1.62 x 10-6 mm3/Nm and 6.63 x 10-7 mm3/Nm at 25 degrees C and 750 degrees C, respectively. It is noted that MoS2 and Mo2N were preferential oxidation in comparison to CrN was conducive to lubrication at medium and high temperature. Additionally, a continuous protective glaze layer was generated within the wear track of the composite coating at 750 degrees C which was mainly consist of MoO3 generated in situ by the oxidation of Mo com-pounds with a higher affinity for oxygen. Meanwhile, the hard phase of CrN with outstanding oxidation resis-tance play a good bearing role during the friction process. This new type of composite coating provides a potential solution for the application of high-temperature wear-resistant coating under harsh working conditions for mechanical engineering.