Microstructure and high-temperature tribological characteristics of self-lubricating TiAlSiN/VSiN multilayer nitride coatings

In recent years, self-lubricating hard protective coatings operated at elevated temperature have drawn great amount of attentions. It has been found that alloying certain elements such as vanadium is an effective method to reduce the friction coefficient, since the Magnéli phase formed at elevated temperature provides a self-lubricious surface during the wear process. However, the formation kinetics of the Magnéli phase should be appropriately controlled. Insufficient or excessive amount of Magnéli phase formation may result in high friction coefficient or severe oxidation of coatings. This study reports an architectural design strategy to engineer the mechanical and high temperature tribological properties of TiAlSiN/VSiN multilayer. In this study, the multilayer system exhibited a low friction coefficient of 0.28 and the lowest wear rate of 7.01 × 10−6mm3N−1m−1 was revealed at multilayer with bilayer period of 16 nm during the wear test at 700 °C. The existence of the Magnéli phase, V2O5, was observed by XPS and its high-temperature lubricating effect was revealed as compared to the wear test at room temperature. It is demonstrated that a particular architectural design of TiAlSiN/VSiN multilayer coating provides a potential candidate for high-speed cutting tools due to their mechanical and lubricious properties.