Tribocatalysis Induced Carbon-Based Tribofilms—An Emerging Tribological Approach for Sustainable Lubrications

Abstract

To comply with the high demand for efficient and sustainable lubrications, carbon-based tribofilms and/or nanomaterials have emerged as a potential solution that can resolve the current major shortcomings of phosphorus- and sulphur-rich tribofilms and protective coatings. Although their employment is still in the early stages of realization and research, these tribofilms receive significant interest due to their capability to continuously and in situ repair/replenish themselves during sliding, which has been an ultimate goal of all moving mechanical systems. Structurally, these tribofilms are complex and predominantly amorphous or disordered with/without graphitic domains (e.g., graphene/graphite, onion-like carbon, etc.). Chemically, the compositions of these tribofilms vary significantly with environments, conditions, and material precursors. Yet, the structural properties of carbon-based tribofilms remain largely ambiguous, which precludes a full understanding of the mechanisms underlying the formation and lubrication performance. This review will summarize the current state-of-art research about the in situ carbon-based tribofilms that have been published since the pioneering works. Particularly, this work will highlight the recent approaches to generate these tribofilms, their associated lubrication performance, current understanding of the formation mechanics, common analytical approaches for these tribofilms, and the compatibility of these tribofilms with other additives. Together, the overall outlooks will be drawn, demonstrating the knowledge gaps and proposing further investigation tactics to tackle these emerging issues.

Tribological Analysis of Steels in Fuel Environments: Impact of Alloy Content and Hardness

“…Prior studies indicated that Cr 2 O 3 is able to catalyze the formation of oligomers/polymers from polyalphaolefin and dodecane [43]. Given that the tribotesting was conducted in the air, the formation of Cr 2 O 3 from Cr in D2 during testing aligns with these findings.…”

“…The Raman spectra indicated the presence of characteristic carbon D and G bands, at approximately 1350 cm −1 and 1580 cm −1 , respectively. These Raman signatures have frequently been associated with the formation of carbon-based tribofilms [37][38][39][40][41][42][43][44][45]. The acquired series of Raman maps, spectra, and energy-dispersive x-ray spectroscopy (EDS) maps demonstrated the formation of carbon films during the sliding process.…”

“…The Raman spectra indicated the presence of characteristic carbon D and G bands, at approximately 1350 cm −1 and 1580 cm −1 , respectively. These Raman signatures have frequently been associated with the formation of carbon-based tribofilms [37][38][39][40][41][42][43][44][45]. Figure 7a shows how the steel samples behaved in terms of friction when they were paired with alumina as the counterbody material.…”

Synergism of TiO2 and Ni on the Growth of a Double-Layered Tribofilm: New Strategy for ZDDP Replacement

“…We assume that the mild abrasion marks on the worn surface can be caused by the TiO 2 particles released at the friction interface or/and protruding peaks on the surface of the tribofilm. From Figure c, only a few abrasion marks are noticed from the worn surface of 5 N /5M/PF, as is ascribed to formation of the carbon-based tribofim. − The worn surface of 3 N /3T/5M/PF is rather smooth and abrasion furrows are rarely observed from Figure d.…”