Nano additive CeO2 without sulfur and phosphorus was used in combination with molybdenum dithiocarbamate (MoDTC) to solve the problems of low load-bearing capacity and unsatisfactory ...friction-reducing property of organic molybdenum in lubricating grease. By using quartz crystal microbalance (QCM) to analyze the adsorption behavior of the composite additive, it was found that the viscoelastic co-adsorption behavior of MoDTC and CeO2 nanoparticles significantly improved the adsorption rate and equilibrium adsorption mass, which made the PB value of the composite additive increased by 77.6 % and 12.6 % compared with CeO2 and MoDTC, respectively. In the tribofilm formed by composite additive, CeO2 nanoparticles that do not undergo frictional chemical reactions with MoDTC form a flat and hard intermediate layer in the tribofilm, which improves the bearing capacity and effectively suppresses the fluctuation and accumulation of layered MoS2 on the surface. The layered structure is concentrated on the surface of the tribofilm and parallel to the friction direction, significantly reducing the sliding resistance between layers. Therefore, a thinner MoS2 layer with appropriate orientation is more conducive to improving the friction reduction performance of the grease. This results in a 33.9 % decrease in the friction coefficient of organic molybdenum, while its load-bearing capacity increases from 900 N to 1400 N, enabling lithium complex grease to achieve low friction, low wear, and high load simultaneously.
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Sulfide was used as solid lubricant, and MoS2 was popular. It was used industry as powder shape. Sulfur as oil additive; ZDDP, MoTDC were also well known. These composites make tribofilm which ...prevent seizure, scoring and some tribological troubles. In this paper, sulfides were synthesized by powder metallurgy technics. In addition, these sulfides were mixed with bronze powders and sintered as cylindrical specimen. As a result of the friction test in the lubricated condition, tribofilm were covered with specimen surface. By XPS observation, sulfides and oxides were detected on the specimen surface. In the test, additive was not contained in the lubricant because PAO as base oil was adapted. However, sulfide in the specimen affect the making the tribofilm, especially when bornite (Cu5FeS4) was used.
The poor dispersibility, strong interlayer interaction, and inferior crack resistance ability restrict the employment of graphene as a lubricant additive. Herein, we prepared fluorinated graphene ...with different F/C ratios by direct fluorination of multilayer graphene utilizing F2. Among them, highly fluorinated graphene (HFG) with an F/C ratio of about 1.0 presented prominent thermal stability and excellent tribological performance as an oil-based lubricant additive, whose friction coefficient and wear rate had a 51.4 and 90.9% decrease compared to that of pristine graphene, respectively. It was confirmed that C–F bonds perpendicular to the graphene plane contributed to increasing the interlayer distance and tribological performance of fluorinated graphene, while the randomly oriented CF2 and CF3 groups did not count as influential, as demonstrated via X-ray diffraction, X-ray photoelectron spectroscopy, and polarized attenuated total reflection-Fourier transform infrared spectroscopy. Meanwhile, Raman measurements traced the formation process of integrated and stable HFG tribofilm during friction process, and the corresponding stability was attributed to the physical and chemical interactions between HFG and friction pairs. More interestingly, the outstanding crack resistance ability of HFG preserved the sheet structure from destruction due to decreased in-plane stiffness and out-plane stress, thus constructing the tough tribofilm. The simple and feasible preparation makes HFG a promising candidate as advanced lubricant in industrial fabrication.
•Black phosphorus dotted with Ag nanoparticles is synthesized by a facial and in-suit chemical reduction approach.•The nanocomposite of Ag/BP is an excellent lubricant additive achieving ultralow ...friction and excellent wear resistance.•Ag/BP can act as a catalyst to decompose the base PAO oil forming a carbon-based tribofilm during rubbing process.•The formed tribofilm consisting of BP and amorphous carbon corresponds to the superior lubricating ability of Ag/BP.
Black phosphorus (BP) is a new two-dimensional (2D) material with attractive nanoscale chemical and physical properties. Herein, black phosphorus dotted with silver nanoparticles (Ag/BP) was synthesized via a facile and in-suit chemical reduction approach without reductant. The tribological properties of as-prepared Ag/BP nanocomposite as lubricant additive in poly-alpha-olefin (PAO6) based oil were investigated by a ball-on-disc tribometer. The results demonstrate that the oil dispersed with trace amount of Ag/BP nanoadditives shows excellent lubricating performance for the steel/steel contact. The friction coefficient and wear rate of the oil dispersed with 0.075 wt% Ag/BP nanoadditives are reduced by 73.4% and 92.0% respectively, as compared to the based PAO6 oil. The possible friction-reducing and anti-wear mechanisms of Ag/BP nanoadditives in oil are illustrated by analyzing the wear scar surfaces. During scratching, the Ag/BP nanomaterials serves not only as a friction-reducing and anti-wear additive, but also as a catalyst to decompose the based PAO oil for forming a carbon-based tribofilm under ambient condition that further reduces the friction and wear. The findings here provide a novel insight into the design of lubricant additive incorporated in base oil and suggests a new potential application of black phosphorus in lubrication and tribology.
MXenes induce excellent wear resistance under solid lubrication due to their distinctive surface chemistry, easy-to-shear ability, and capability to form low-friction and wear-resistant tribofilms. ...However, beyond the extensively studied Ti3C2Tx, other promising members of the MXene family remain largely underexplored. Therefore, we spray-coated multi-layer vanadium carbide (V2CTx) coatings (thickness ∼10.8 μm) on steel substrates and studied their tribological performance for prolonged times (10,000 cycles) using a reciprocating ball-on-disk tribometer with acting contact pressure of 445 MPa in ambient conditions. Results show that V2CTx-coated substrates demonstrate an 8-fold reduction in friction (COF of 0.11) and a 10-fold wear rate reduction (1.405 × 10−6 mm3 N−1 m−1). High-resolution materials characterization confirmed that the remarkable tribological performance of these coatings can be traced back to the formation of protective films on the substrate (tribofilm) and counterbody (transferfilm) consisting of contact pressure and frictional heat-induced degraded, deformed, exfoliated V2CTx nanosheets, nanocrystalline oxides, and amorphous carbon debris. This work fully elucidates the tribological potential of V2CTx, which is of utmost relevance for designing high-performance lubricating materials. Our work has assessed the performance of multi-layer V2CTx (M2XTx) due to its remarkable thermal stability, low molecular weight, good mechanical properties, and high interlayer spacing, thus serving as an entry point into diverse MXene compositions, including M4X3Tx (V4C3Tx).
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In pursuit of energy efficiency and durability throughout human history, advances in lubricants have always played important roles. Ionic liquids (ILs) are room-temperature molten salts that possess ...unique physicochemical properties and have shown great potential in many applications with lubrication as one of the latest. While earlier work (2001–2011) primarily explored the feasibility of using ILs as neat or base lubricants, using ILs as lubricant additives has become the new focal research topic since the breakthrough in ILs’ miscibility in nonpolar hydrocarbon oils in early 2012. This work reviews the recent advances in developing ILs as additives for lubrication with an attempt to correlate among the cationic and anionic structures, oil-solubility, and other relevant physicochemical properties, and lubricating behavior. Effects of the concentration of ILs in lubricants and the compatibility between ILs and other additives in the lubricant formulation on the tribological performance are described followed by a discussion of wear protection mechanism based on tribofilm characterization. Future research directions are suggested at the end.
Nanomaterials have garnered significant interests owing to their attractive tribological potentials. Although numerous investigations pertaining to nano-reinforced composites have been conducted, the ...critical interactions between multidimensional nanoadditives and tribofilms are yet to be reviewed comprehensively. This review critically examines the current state of multidimensional nanomaterials that serve as functional additives in tribology. After brief discussion on major characteristics of multidimensional nanoadditives, the formation mechanisms of a tribofilm under the solid/liquid lubrication states are elaborated, and the functions of multidimensional nanoadditives are discussed. Additionally, concise conclusions regarding the formation mechanism and influencing factors of nano-tribofilms under solid/liquid lubrications are provided. The current challenges and prospects are presented such that the understanding of nano-tribology can be further intensified and their practical applications diversified.
Nanofluids containing nanocomposite materials have broad application prospect in lubrication. In the present study, MoS2-Al2O3 nanocomposite was synthesized by solvothermal method. Then water-based ...nanofluid containing MoS2-Al2O3 nanoparticles was prepared and it exhibited optimal stability and wettability. The tribological properties of MoS2-Al2O3 nanofluid under steel/steel contact were investigated. Through chemical analysis of worn surface, tribochemical reactions occurred and tribofilm generated at friction interface were studied to reveal the lubrication mechanism. The results showed that MoS2-Al2O3 nanofluid exhibited outstanding effect on reducing the friction force and wear rate of friction pairs. The superior lubrication performance was partly attributed to the entry and movement of nanoparticles at friction interface. More importantly, due to interfacial tribochemistry, a tribofilm with double layer structure composed of adsorption film and reaction layer was formed on the metal surface, preventing the direct contact of steel surfaces. The adsorption film with a thickness of about 16 nm was predominated by amorphous substrates and crystal phases (ultrafine Al2O3 and MoS2 debris) embedded in the top. And the reaction layer beneath adsorption film contained high mechanical properties iron oxides (mainly Fe3O4 and Fe2O3) and self-lubricating Fe2(SO4)3, which further alleviated friction and enhanced the wear-resistance of materials.
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•MoS2-Al2O3 nanocomposite was synthesized and applied as lubricating additive.•MoS2-Al2O3 nanofluid showed excellent performance under steel/steel contact.•A double-layered tribofilm due to interfacial tribochemistry was formed on surface.•Iron oxides and Fe2(SO4)3 in reaction layer further alleviated friction and wear.
2 H-MoS2 nanoparticles with excellent structural characteristics has become one of the main research objects of lubricating additives. Herein, one crumpled MoS2 submicrosphere staggered by ultrafine ...nanosheet was successfully synthesized by clean and fast laser irradiation in liquids at ambient conditions. Such crumpled sphere exhibits good wettability on steel surface in water. As water additives, the crumpled MoS2 submicrosphere can significantly improve the lubrication performance. Notably, the crumpled MoS2 submicrosphere have remarkable anti-friction with 80% reduction of COF compared with the pure water. The enhanced lubrication performance benefits from the lamella structure, microbearing and protective tribofilm of crumpled submicrosphere.
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This research presents the analysis of metrologic and tribologic aspects of machined surfaces obtained after turning with the application of various cooling/lubricating methods. The thoroughly ...conducted machining tests are: dry machining, minimum quantity cooling lubrication (MQCL); minimum quantity cooling lubrication with EP/AW modifications (MQCL+EP/AW) and minimum quantity lubrication (MQL). The phosphate ester based modification in the MQCL+EP/AW method is employed in order to increase the lubricating properties of the emulsion. The surface topography, responsible for the tribological properties of mating parts, is measured. The smallest values of the surface roughness are obtained after turning under MQCL+EP/AW conditions, while the highest values of parameters responsible for oil retention in mating parts are obtained after machining with the MQL method.
•Relations between machined surface integrity of AISI 1045 steel and tribology.•Occurrence of tribofilm on machined surfaces after MQCL+EP/AW and MQL.•Decreased volumetric wear on samples after MQCL+EP/AW and MQL.•Lowest friction coefficient obtained for surface after MQCL + EP/AW.
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