Stable and durable TiBN-Cu/polyalphaolefin(PAO) composite lubrication system: Enhanced lubrication performance through PAO physicochemical adsorption

This paper focuses on the fabrication of a series of TiBN-Cu films with varying B content using a non-equilibrium magnetron sputtering process. The microstructure, mechanical properties, and tribological performance under polyalphaolefin(PAO) lubrication of these films were fully investigated. The results indicate that the TiBN-Cu films are composed of fcc-TiN, fccCu, hcp-TiB2, and α-BN. Under PAO6 lubrication, the friction coefficient and wear rate of the TiBN-Cu/PAO composite system first decrease and then slightly increase. The mechanisms behind the enhanced lubrication behavior in terms of wear and friction of the composite system were thoroughly investigated, focusing on the lubrication state, PAO molecular adsorption behavior, and tribochemical products. The lubrication state revealed that the surface roughness of the films directly affects the continuity of the oil film. Calculations of the surface energy revealed that the surface energy of the films decreases gradually with increasing B content, exhibiting oleophilic characteristics that are conducive to the spread of PAO6 on the film's surface. Based on Density functional theory(DFT), calculations of the adsorption energy in the composite system indicated the formation of a robust physicochemical adsorption layer on the surface of the TiBN-Cu/PAO composite. Raman spectroscopy and transmission electron microscope(TEM) analyses of the tribochemical products revealed the in-situ generation of an amorphous carbon‑hydrogen lubricating film with good lubricating performance on the TiBN-Cu composite film under PAO6 lubrication, due to a friction-induced catalytic effect. Additionally, molecular dynamics(MD) simulations based on the theory of molecular dynamics were conducted to explore the degradation process of PAO6 molecules in the solid-liquid composite system under friction, clarifying the “adsorption, dehydrogenation, carbon chain breaking, and carbon chain reconstruction” process in the TiBN-Cu/PAO system. These aspects collectively contribute to enhancing the tribological performance of the TiBN-Cu/PAO composite system. A durable, stable, and efficient TiBN-Cu/PAO solid-liquid composite lubrication system under in-situ and ambient conditions was achieved in this paper. [Display omitted] •An stable and durable TiBN-Cu/PAO solid-liquid lubrication system in situ at room temperature was accomplished.•The influencing factors of the solid-liquid system were fully investigated regarding to the lubricati