Improved tribological property of VN film with the design of pre-oxidized layer

Abstract At room temperature, VN films often have a relatively high friction coefficient (COF), which vastly limits their industrial application. In this work, pre-oxidation thermal treatments with different oxygen concentration were applied to improve the room-temperature tribological properties of VN films. The results showed that the V2O5 and VO2 thin pre-oxide layer form under the high and low oxygen concentration, respectively, and after thermal treatment, the tribological properties of VN films are promoted greatly. The VN film with V2O5 thin pre-oxide layer has the lowest COF (~0.23) but the greatest wear rate ((11.41 ± 0.22)× 10–15 m3 N−1 m−1), while the VN film with VO2 thin pre-oxide layer has a relative lower COF (~0.46) as well as wear rate ((2.27 ± 0.14)× 10–15 m3 N−1 m−1) than VN film without a pre-oxide layer. By analysis, the initial existence of V-oxide seems to have a more positive effect than in-situ formation of V-oxide on the improvement of tribological property at room temperature, and the V2O5 plays a decisive role in the decrease of COF, and the VO2 can improve the properties of anti-friction and wear resistance simultaneously. Thus designing a thin pre-oxide layer on the V-based films seems to be a promising method to promote their room-temperature tribological property.