Microstructure, chemical states, and mechanical properties of V–C–Co coatings prepared by non-reactive magnetron sputtering

• Nanocomposite V–C–Co coatings with strong Co/VC interfaces were formed.
• Found nanocrystalline VC grains separated by ~ 1 nm thin Co-rich ligaments.
• A noticeable amount of CCo bonds between VC and Co is identified.
• V–C–Co coatings exhibited a higher plasticity characteristic than VC.

V–C–Co coatings have been prepared by non-reactive magnetron co-sputtering from VC and Co targets. The microstructure, chemical states, and mechanical properties are examined as a function of Co content in the coatings. The coatings are dense, with columnar growth structures. High resolution transmission electron microscopy (HRTEM) studies identify a nanocomposite microstructure for the 12.4 at.% Co coating, in which ligament-like Co-rich regions partially separate the nanocrystalline VC grains. X-ray photoelectron spectroscopy studies reveal a noticeable charge transfer from Co 2p states to C 1s states. This charge transfer, in addition to the ligament-like Co-rich regions as revealed by HRTEM, points to the formation of a strong Co/VC interface. The nanoindentation hardness of the coatings drops steadily with the Co content, from 29 GPa for pure VC to ~ 21 GPa for the 12.4 at.% Co coating. Meanwhile, the plasticity characteristic increased from 0.42 to 0.53.