Preparation and Properties of Polysilazane/MoS2 High Temperature Self-Lubricating Coatings

High-temperature solid self-lubricating coatings have found extensive applications in aviation, aerospace and various other fields, owing to their remarkable tribological properties and adhesive characteristics. In this study, a novel wide-temperature range anti-friction and anti-wear coating in simple composition was prepared based on polysilazane, which could be converted into a high hardness inorganic amorphous ceramic phase SiOC at high temperatures as the film-forming materials with excellent interfaced bonding strength and wear resistance property, and MoS2 as the lubrication phase. The effects of various factors on the tribological properties of the coatings were systematically investigated, the microstructures, phase compositions and wear mechanism of the coating were analyzed through SEM, XRD, Raman and pencil hardness characterization. The results indicated that the polysilazane/MoS2 coatings prepared at lower heat treatment temperatures (25~300 ℃) exhibited excellent adhesion to the metal substrate. However, at high temperature (500 ℃), the mass loss of polysilanze during the ceramic conversion process led to crack formation and poor adhesion, primarily due to the substantial density increased and volume shrinkage of polysilazane during conversion to ceramics. Additionally, the coating demonstrated exceptional anti-friction and anti-wear properties over a wide-temperature range, spanning from room temperature (25 ℃) to 300 ℃. Specifically, the coating subjected to a 300 ℃ heat treatment performed optimally at 200 ℃, 9 N, and 90 r/min, with an average friction coefficient of 0.05 and a wear rate of 7.6×10−5 mm3/(N·m). This coating exhibited outstanding lubrication and wear resistance at medium-high temperatures, primarily attributed to the unique layered structure of MoS2 and its weak shear stress properties. However, as the heat treatment temperature reached 500 ℃, the average friction coefficient and wear rate of the coating increase significantly. This was mainly due to the oxidation of MoS2 in the coating to MoO3 with poor lubricating properties. Furthermore, the average friction coefficient of the coating showed a slight tendency to increase as the adhesive content in the coating increased, but the wear rate decreased with the increase in adhesive content. The coatings exhibited low friction coefficients and wear rates on a wide range of substrates, demonstrating their generalizability. Moreover, the coatings maintain low friction coefficients and wear rates under different loaded and rotation speeds. The successful development of this coating was expected to provide an experimental basis and theoretical guidance for enhancing surface lubrication protection for parts and components operating in room temperature to high temperature working conditions. © 2024 Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. All rights reserved.