Study on properties and tribological behaviors of silicon nitride-based Ti-DLC films

Abstract

Silicon nitride is widely used in ceramic bearings. Silicon nitride-based Ti-DLC films with different low doped Ti content were prepared by multifunctional high frequency magnetron sputtering system, to expand the application of silicon nitride in aerospace and modern industry by improving its tribological properties. SEM, Raman, XPS and AFM were used to analyze the structure and composition of the films. The mechanical properties were measured by nanoindentation and scratch test. The tribological performances were studied at room temperature and the friction and wear mechanism was analyzed. Ti-DLC films with low doped Ti content present a dense amorphous structure. The content of sp³-C in Ti-DLC films increases first and then decreases, with the increase of doped Ti content. It means that the increase of doped Ti content improves the hardness, elastic modulus and the adhesion behaviors. Moreover, the increase of doped Ti content reduces friction coefficient and wear rate, which is beneficial to tribological performance. The tribological performances of silicon nitride-based Ti-DLC films are optimal when the doped Ti content is 0.64 at. %, and the average friction coefficient is as low as 0.006 which is close to super slippery and the wear rate is 3.68 × 10⁻⁷ mm³·N⁻¹·m⁻¹. The design prepared the ultra-low friction Ti-DLC film on the silicon nitride can reduce harmful friction losses, creating application possibilities of silicon nitride in harsh conditions. Particularly, it provides new ideas and technical support for the manufacture of self-lubricating silicon nitride bearings.