Insights into friction properties and mechanism of self-lubricating MoVN–Ag films at high temperature

Abstract

MoVN is a promising high temperature lubricating material. In this study, the MoVN–Ag films with different content of Ag are synthesized for lubrication in wide temperature range using pulsed DC reactive magnetron sputtering. The effect of Ag content on the mechanical properties and tribological behavior of the films at 25 °C, 300 °C, 500 °C and 700 °C is investigated. The results reveal that although the doping of silver is detrimental to the mechanical properties of MoVN films, it can improve the tribological properties of the films. The optimized MoVN–Ag film with Ag content of 45.6 at.% shows a promising self-lubricating performance and low wear rate at different test temperatures. The average friction coefficients are as low as about 0.19 and 0.28 at 500 °C and 700 °C, respectively. There are different friction mechanisms at the test temperatures: Ag diffused self-lubricating film at 500 °C, as well as Magnéli and double oxide easy shear phases formed at 700 °C, dominate the low friction behavior of the MoVN–Ag films.