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As technology progresses, lubricant additives are becoming more prevalent and expanding the application areas of modern tribology. This study aimed to investigate the tribological properties of recently used additive particles and their impact on worm gearbox power consumption. To achieve this, hazelnut oil was chosen as the base oil, and graphite, boric acid (BA), and hexagonal boron nitride (hBN) particles were added in certain proportions. The effect of each additive on the coefficient of friction and wear was investigated under different operating speeds and loads using a pin-on-disc tester. Optimal additive ratios for worm gearbox oils were utilized based on the previous studies, and oils using hazelnut oil as the base were prepared accordingly. The efficacy of the additives was evaluated using a worm gearbox test system. [ABSTRACT FROM AUTHOR]

According to the redox ability of dopamine in a weak alkaline environment, silver nanoparticles were uniformly loaded on the surface of polydopamine-modified graphene oxide (Ag/PGO). The results show that the base oil containing Ag/PGO nanoparticles exhibits a better tribological property than base oil. The maximum decrease in wear rate and friction coefficient at different temperatures amounted to 68% and 53.6%, respectively. The tribofilm containing C, O, N, and Ag exists and plays an important role in reducing friction and increasing wear resistance. Molecular dynamics simulations show that the microscopic oil film composed of Ag/PGO and n-hexadecane has low shear deformation during the shearing process, and the oil film has low interaction energy with the upper and lower shear walls. [ABSTRACT FROM AUTHOR]

In the boundary lubrication regime, the addition of long as well as straight alkyl chain containing additive exhibit a serendipitous impact on protecting various metallic surfaces or machinery components from friction and subsequent wear. In quest of environment-friendly, proficient friction-reducing, surface protective and cost-effective lubricant additives; herein, two diazomethine functionalised long-chain consisting organic molecules, namely (3E)-N-((E)-2-(octadecylimino)ethylidene)octadecan-1-amine (ODE) and (3E)-N-((E)-2-(dodecylimino)ethylidene)dodecan-1-amine (DDE) were synthesized through a one-pot condensation reaction. The surface protective film-forming, as well as wear and friction reducing properties of these organic additives on steel balls within paraffin oil (PO), were thoroughly explored using a four-ball tester with variation in time, load and speed. The addition of these additives showed a remarkable reduction of coefficient of friction (COF) and wear amount in compared to the pure base oil. ODE exhibited better performance with a ∼62% reduction in COF and ∼23% reduction in wear amount for steels in contact. Electronic level analysis for elucidating the tribofilm formation capability of the additives was rationalized using computational approaches such as density functional theory (DFT) and Fukui indices. Additionally, the molecular dynamics (MD) simulation which is an efficient computational approach was used to explore the spontaneous adsorption insight of additives; and also radial distribution function (RDF) were analysed to impressively explore the molecular-level interactions and adsorption mechanism of the additives with the metal atoms. Thereby, the mechanism of surface adhesive tribofilm formation and its metal protection capability has been explained in a comprehensive manner. Diazomethine functionalised organic molecules were synthesized with a variation of aliphatic chain length. Long aliphatic chain containing ODE additive showed enhanced surface protective performances in paraffin oil exhibiting lower COF value in comparison to DDE. Possible formation of ODE-based efficient tribofilm in metal-solution interface which exhibits enhanced surface adsorption property on the metal surface. Substantial decrease in wear upon addition of ODE in the base oil, which was confirmed by FE-SEM and 3D surface profilometer study. MD simulation has been used to investigate the adsorption competence of ODE and DDE on the iron surface. [ABSTRACT FROM AUTHOR]

With the EU aiming for net-zero greenhouse gas emissions by 2050, conventional production cycles must be transformed into cradle-to-cradle approaches. Spent coffee grounds are often dumped in landfills, with their potential as high-quality feedstock for biofuel or bio-lubricant production. Spent coffee grounds oil (SCGO) was investigated for its physicochemical properties while having more free acid groups compared to the reference polyalphaolefin 8 (PAO 8), which may cause faster oxidation. TGA results displayed comparable thermal stability of SCGO and PAO 8 for inert/oxidative atmosphere. The oil composition was characterized by ATR-FTIR, elemental analysis, and GC-EI-MS, where a higher oxygen content was found for SCGO, referring to functional ester/acid groups. The tribological behavior of SCGO was studied as lubricant base oil and as a 5% additive in PAO 8. The condition of fresh and tribologically used oils was investigated with High-Resolution-ESI-MS, and the worn surfaces were evaluated by light microscopy and topographic analysis. The results showed a superior friction coefficient of pure SCGO (μ = 0.092) to PAO 8 (μ = 0.129). The 5% SCGO additive in PAO 8 (μ = 0.095) could significantly reduce friction compared to pure PAO 8 on an unpolished 100Cr6 surface. [ABSTRACT FROM AUTHOR]

n the last few years, there is a general shift observable toward greener lubrication, fueled amongst others by policy initiatives such as the European Green Deal in consistency with the UN Sustainable Development Goals. At least 70 vol% of a lubricant is composed of a specific base oil, the rest is a variation of additives altering the lubricant properties (enhancing or suppressing existent base oil properties or adding new properties) to be operational for a particular field of application. So, in terms of sustainability, biodegradability, bioaccumulation, and toxicity the type of base oil plays a major role, which makes environmentally harmful petroleum-based lubricant formulations highly problematic for future applications. Hence, this leads to an ever-growing demand of environmentally friendly lubricant alternatives. Within the scope of this review lies the investigation of bio-based, bio-derived, and other sustainable lubricant components that could serve as promising replacements for conventional petroleum-based formulations, in accordance with the principles of green chemistry and tribology. As recycling is embraced by the term sustainability, waste-derived components of non-biological origin are also included in this work. An overview of studies on the tribological performance such as friction and wear properties of these sustainable and benign lubricant components is given. [ABSTRACT FROM AUTHOR]

Elastomeric rotary shaft seals are a common seal type for various industrial applications. They are comparably cheap and easy to use and offer an overall good performance. But the wear behavior of these sealing systems is not fully understood and not predictable so far. If a lip seal fails, it causes high maintenance costs and environmental damage. In this article, various tribological conditions are considered. For this purpose, the sealing systems are tested with multiple operating conditions relevant to practice. Three test series are conducted with rotary shaft seals BAUM5X7 75FKM585 on plunge ground shafts. The tests are carried out with two different circumferential velocities of the shaft (4.2 and 10 m/s), three different oil sump temperatures (40, 80, and 120 °C), two different lubricant types (FVA 3 and PG 3), and five different test durations (between 100 and 625 h). For a complete acquisition of the system condition, all shaft surfaces are measured in 2D and 3D before and after the test runs and the wear of the sealing edges is evaluated with a recently developed laser line triangulation method on the complete circumference of the sealing rings. Results show large amounts of wear, depending significantly on the operating conditions. A strong correlation of the wear effects in the tribocontact area of the sealing system becomes evident. This article helps to understand and avoid critical operating conditions concerning abrasive wear. [ABSTRACT FROM AUTHOR]

Oils and grease have beneficial effects on moving parts such as connecting rod, gears, shafts, and engine to reduce wear and friction. The properties of lubricants such as tribological and rheological properties are an important role in oils and grease characterization. Nano additives on lubricant oils play an important role in anti-wear; reduce the coefficient of friction and enhance the rheological properties. The Tribological and rheological behavior of base oil 15W50 which have different concentrations of multi-wall Carbon Nanotubes (MWCNTs) (0.5, 1, 1.5, and 2 wt%), and constant amount of graphene nanosheets (GNSs) (0.5 wt%) were investigated. This research is the first one in studying the effect of hybrid nano additives of (MWCNTs) and (GNs) on the tribological and rheological properties of lubricant oils. Tribological characterization was carried out on four ball testing model under different loads (200, 400, 600, and 800 N). The kinematic viscosity, flash point, pour point, and thermal conductivity of nanofluid added 15W50 lubricant are estimated and compared with base oil. The results showed that nano additives improve the wear scar and coefficient of friction by 78% and 48%, respectively. The flash point, thermal conductivity, kinematic viscosity, and pour point, were improved by 15%, 77%, 76.8%, and 20%, respectively compared with the base oil. The hybrid addition of CNTs/GNs nanoparticles enhanced the properties of 15W50 engine oil. [ABSTRACT FROM AUTHOR]

The tribological performance of polymer-stabilized TiO2 particles dispersed in mineral base oil was investigated. Two polymer–TiO2 mass ratios were investigated, with a constant polymer concentration of 0.3 wt% and two nanoparticle concentrations of 0.1 and 1 wt%. Friction tests were carried out with a pin-on–reciprocating flat test configuration under boundary-lubricated sliding conditions in the presence of a steel–steel contact and at two temperatures (20 and 100 °C). The results show the very good antiwear performance of the nanoparticle-based dispersions. The most promising results were obtained with 0.1 wt% TiO2 particles and at 20 °C. At this temperature, the wear resistance properties of the TiO2 particles surpass those of zinc dialkyldithiophosphate (ZDDP). The tribofilms generated during the friction tests were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS). A tribofilm composed of agglomerates of TiO2 particles embedded in a matrix formed by the polymer was observed. The combination of the polymer used as a dispersant and the TiO2 particles allows good tribological performance that was observed during the friction tests. The formulation including TiO2 particles could improve the antiwear properties of materials in an environment where conventional wear reducing additives do not form tribofilms due to low temperatures. [ABSTRACT FROM AUTHOR]

The proposed work deals with the investigation of magnetorheological based minimum quantity lubrication of graphene oxide (GO) based jojoba oil as bio-lubricant on machinability and tool wear mechanism of turning Monel K500 alloy. Experiments were carried out for dry, flooded, minimum quantity lubrication (MQL) and magnetorheological (MR–MQL) conditions using medium duty lathe. The process parameters include the cutting speed 95, 110, 125 m/min, feed rate 0.050, 0.075, 0.1 mm/rev and depth of cut 0.25, 0.50, 0.75 mm for the output responses such as surface roughness, cutting temperature and tool flank wear. The results indicated that GO-based bio-lubricant MR–MQL reduced coefficient of friction (COF) of 0.051 and wetting angle of 6°, as well as improved machining performance such as cutting temperature of 145 °C, the surface roughness of 0.614 µm, flank wear of 0.18 mm with enhanced lubrication regime under extreme wear conditions. [ABSTRACT FROM AUTHOR]

This study investigates the performance of three ionic liquids (ILs), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate, trihexyl(tetradecyl)phosphonium decanoate, and 1-butyl-3-methylimidazolium tetrafluoroborate, as lubricant additives in synthetic oil polyalphaolefin (PAO8) and bio-based oil trimethylolpropane trioleate (TMPTO). The ILs were added at 0.5, 1.0, and 1.5 wt% concentrations and evaluated in terms of their miscibility with base oils as well as friction- and wear-reducing abilities. Four-ball and high-frequency reciprocating rig (HFRR) tribotesters were employed to evaluate the tribological performance under a boundary lubrication regime. Worn steel surfaces were characterized using optical microscopy, profilometry, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. The results suggested that the addition of trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate and trihexyl(tetradecyl)phosphonium decanoate improved the tribological performance of both PAO8 and TMPTO at an optimum concentration of 1 wt%. They showed good friction reduction, lower overall surface wear, and improved surface finishing. 1-Butyl-3-methylimidazolium tetrafluoroborate managed to improve the tribological performance of both base oils only at 0.5 wt%. A further increase in 1-butyl-3-methylimidazolium tetrafluoroborate concentration caused detrimental effects on the steel surface due to the formation of halogenic compounds. [ABSTRACT FROM AUTHOR]