Mutual promotion on the mechanical and tribological properties of the nacre-like self-lubricant film designed for demanding green tribological applications
Year: 2024
Type: article
Abstract: The inverse relationship between tribological and mechanical properties of environmental friend self-lubricant films, induced by adding soft lubricant agents which can diffuse fast 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 a novel nacre-like multilayered Mo2N-SiNx/Ag-SiNx self-lubricant films, using a RF magnetron sputtering system, for real applications where harsh conditions at elevated temperatures exist. The multilayered films, deposited by alternating deposition of Mo2N-SiNx and Ag-SiNx modulation layers, exhibited tri-phases of fcc-Mo2N, fcc-Ag and SiNx, where SiNx encapsulated the nano-crystalline Mo2N 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 Ag-SiNx layers, below 6 nm, on the Mo2N template resulted in an extraordinary increase in both hardness and elastic modulus, able to block the serious degradation of the mechanical properties by the addition of Ag. The room temperature anti-friction property could be enhanced by the increase of the Ag-SiNx layer thickness due to the excellent lubricant nature of Ag acting in synergy with Mo2N, while the wear-resistance was due to the high mechanical strength giving rise to values below 4×10-8 mm3/(N.mm). 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. This behavior was justified by the synergism between the lubricant action of Ag and Mo2N, and the tribo-phase transformation from Ag2Mo4O13 to Ag2MoO4.
Source: Friction
Language: English
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W4405121976