Mutual promotion on the mechanical and tribological properties of the nacre-like self-lubricant film designed for demanding green tribological applications

Ju, Hongbo (author)

The inverse relationship between the tribological and mechanical properties of environmentally friendly self-lubricant films, induced by the addition of soft lubricant agents that can diffuse quickly at elevated temperatures, has hindered the widespread use of these materials in industrial applications. This paper took this challenge to break through the above established relationship by developing novel nacre-like multilayered $Mo_2N$–$SiN_x$/Ag–$SiN_x$ self-lubricant films via an radio frequency (RF) magnetron sputtering system for real applications where harsh conditions at elevated temperatures exist. The multilayered films, deposited by alternating deposition of $Mo_2N$–$SiN_x$ and Ag–$SiN_x$ modulation layers, exhibited three phases of face-centered cubic (fcc) $Mo_2N$, fcc Ag and $SiN_x$, where $SiN_x$ encapsulated the nano-crystalline $Mo_2N$ and Ag phases in each layer to successfully induce a “brick and mortar” nacre-like microstructure (in the area without the coherent structure). The epitaxy growth of the Ag–$SiN_x$ layers with thickness below 6 nm on the $Mo_2N$ template resulted in an extraordinary increase in both the hardness and elastic modulus, which was able to prevent severe degradation of the mechanical properties caused by the addition of Ag. The room-temperature anti-friction property could be enhanced by increasing the Ag–$SiN_x$ layer thickness due to the excellent lubricant nature of Ag, which acts in synergy with $Mo_2N$, while the wear rate below $4×10^{−8}$ $mm^3$/(N·mm) was due to the high mechanical strength. The tribological properties at 600 °C also benefited from the interlocked multilayered architecture, which allowed an extreme low friction coefficient of ~0.12 and a negligible wear rate (WR). This behavior was attributed to the synergism between the lubricant action of Ag and $Mo_2N$ and the tribo-phase transformation from $Ag_2Mo_4O_{13}$ to $Ag_2MoO_4$.

• Language: English
• Keywords: radio frequency (RF) magnetron sputtering system, self-lubricant films, interlocked structure, epitaxial growth, lubrication synergism, tribo-phase transformation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 15 str.
• Numbering: Vol. 13, art. 9440963
• PID: 20.500.12556/RUL-168477
• UDC: 539.92:544
• ISSN on article: 2223-7690
• DOI: 10.26599/FRICT.2025.9440963
• COBISS.SI-ID: 232779779
• Publication date in RUL: 15.04.2025

JU, Hongbo, 2025, Mutual promotion on the mechanical and tribological properties of the nacre-like self-lubricant film designed for demanding green tribological applications. Friction [online]. 2025. Vol. 13, no. 9440963. [Accessed 19 May 2025]. DOI 10.26599/FRICT.2025.9440963. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=168477

Record is a part of a journal

• Title: Friction
• Shortened title: Frict.
• Publisher: Tsinghua University Press
• ISSN: 2223-7690
• COBISS.SI-ID: 525351449

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: radiofrekvenčni (RF) magnetronski razpršilni sistem, samomazalne folije, prepletena struktura, epitaksialna rast, sinergizem mazanja, tribofazna transformacija