Insight into the tribological performance and mechanisms of MoN-Ag/oil solid-liquid lubrication system based on catalytic effect

• Published in: Surface & coatings technology Vol. 480; p. 130612
• Main Authors: Jiang, Yaohong, Wu, Xinmeng, Bian, Shunuo, Chen, Chunyan, Han, Haiwei, Zuo, Bin, Lu, Kun, Zhao, Lijun, Yu, Lihua, Xu, Junhua
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-03-2024
• Subjects: Carbon-based tribofilms; Catalytic effect; Microstructure; MoN-Ag film; Tribological performance; Catalytic effect; Microstructure; Tribological performance; MoN-Ag film; Carbon-based tribofilms
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2024.130612

Efficiently reducing friction and wear in an environmentally friendly lubrication manner remains a challenging endeavor. Here, carbon-based tribofilms with excellent friction-reducing and anti-wear abilities was in-situ formed from the poly-α-olefin oil (PAO6) on the friction interfaces of MoN-Ag composite films. A series of MoN-Ag films were prepared by multi-target magnetron sputtering process. Then, X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Raman, and Fourier-transform infrared (FTIR) spectroscopy, etc. were employed to investigate the microstructures, surface morphologies, mechanical properties of the MoN-Ag films, as well as the tribological performance under the luberication of PAO6 oil. The results showed that the MoN-Ag film consists of γ-Mo2N and c-Ag. With the increase of Ag content, the surface roughness of the films stays increased, while the hardness and elastic modulus of the films initially increase and then decrease. When the content of Ag is 2.7 at.%, the film had the highest hardness (24.1 GPa) and elastic modulus (316.5 GPa), and the MoN-Ag/oil solid-liquid system exhibited the lowest average friction coefficient of 0.087 and the lowest wear rate of 5.8 × 10−7mm3N−1 m−1 after a long duration. The catalytic effect of Ag facilitated the degradation of PAO6 molecules on the friction interface, resulting in the in-situ reorganization and formation of amorphous carbon-based tribofilms with graphite-like structures.
In this paper, PVD technology was utilized to introduce Nano-Ag into MoN comosite films, preparing in a series of MoN-Ag composite films with varying Ag content. Then, the influences of Ag content on the microstructure, surface morphology, mechanical properties of the MoN-Ag films, as well as the tribological performance of these films in base oil, were investigated systematically. The catalytic effect of Ag in the solid-liquid lubrication system and the structure-activity relationship regarding the formation of carbon-based lubricating films from lubricating oil degradation were unequivocally determined. Furthermore, the study delved into the characterization and formation mechanism of in-situ generated lubricating carbon films at the friction interface, revealing the anti-friction and wear mechanisms of the solid-liquid lubrication system. [Display omitted]
•The MoN-Ag film had the best mechanical properties at Ag content is 2.7 at.%.•The excellent tribological behavior under base oil was achieved catalyzed by Ag.•Carbon-based tribofilms was in-situ formed on the friction interfaces of MoN-Ag films.•A long-term, stable TMN/PAO solid-liquid lubrication system is constructed under room temperature.