Effect of Vanadium Addition on the High-Temperature Friction Behavior in Nanostructured Al–Cr–V–N Films Prepared by UBMS

In recent year, vanadium-doped tribological films have become available as possible candidates for self-lubrication at high temperatures. In this work, quaternary Al–Cr–V–N films were deposited onto silicon wafer and WC-Co substrates by an unbalanced magnetron sputtering using high purity (99.99%) CrAl₂ and V targets with argon-nitrogen reactive gases. EPMA results revealed that vanadium atoms can incorporated from 0 to 13 at.% into the films. The maximum hardness value was ~32 GPa at vanadium content of 7.1 at.% in the Al–Cr–V–N films. The high-temperature tribometer was used to analysis the friction characteristics of the films with elevated temperature. As a result of the high temperature friction test after heating up to 700 °C, the average friction coefficient decreased from 0.62 to 0.35 with increasing of vanadium contents in the Al–Cr–V–N films. It is concluded that the reduction of the friction coefficient is attributed to the formation of V₂O₅, which is a Magnéli phase that acts as a lubrication at high temperature.