Friction Behavior of VN Coating under Different Loads

The vanadium nitride (VN) coating was prepared by cathodic arc evaporation system, and the structure, mechanical properties as well as the effect of load on friction behaviors of VN coating was characterized. As a result, the VN coating grew in a dense columnar structure and exhibited NaCl-type face centered cubic structure. Coupled with excellent adhesion strength, the coating also presented good tribological properties. With an increasing load, the friction coefficient of VN coating decreased, while the wear rate increased. According to the Hertzian elastic contact model and the analyzed results of wear debris, it was found that the heavier the load, the greater the interface contact pressure, and the tribo-chemical reaction caused by the heavy load was more intensity. This was benefit of reducing the shear stress and inducing more V element to oxidize as well as generating V₂O₅ lubricating phase, which led to the decreased friction coefficient. Moreover, due to insufficient toughness and poor resistance to plastic deformation, the wear rate of the coating increased with increasing load.