Wear Scar Diameter Research Articles

Influence of ionic liquid/liquid metals on the lubrication properties of lithium grease

PurposeThis paper aims to use an ionic liquid (IL, [HMIM]PF6) to improve the lubrication performance of liquid metal (LM) as a lithium grease additive and to expand the application range of LM.Design/methodology/approachIn this paper, the different mass ratios of [HMIM]PF6/LM mixtures were added into the lithium grease on a four-ball tribo-meter to investigate the effects of its tribological behavior. Scanning electron mircoscope/energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used to reveal the anti-wear and friction-reducing mechanism of the additives.FindingsWhen the load was used at 461 N, the average coefficient of friction (ACOF) and average wear scar diameter (AWSD) of steel ball Lubricated with grease with an optimal ratio of 2:3 ([HMIM]PF6/LM) were reduced by 32.8% and 30.5%, respectively. Friction and wear mechanisms are ascribed to friction-induced additive components that can simultaneously form a composite lubrication film consisting of FePO4, FeF3, Ga2O3, In2O3 and SnO2.Research limitations/implicationsCompared with the pure lithium-based grease, when [HMIM]PF6/LM was added with an optimal ratio of 2:3, the ACOF and AWSD were reduced by 12.4% from 0.097 to 0.085 and 23.8% from 552.117 µm to 420.590 µm under 392 N, respectively. When at 461 N, the ACOF and AWSD of steel ball were reduced by 32.8% from 0.122 to 0.082 and 30.5% from 715.714 µm to 497.472 µm, respectively. It was shown that the simultaneous addition of LM and [HMIM]PF6 can form a composite lubrication film consisting of FePO4, FeF3, Ga2O3, In2O3 and SnO2.Originality/valueIn this paper, [HMIM]P F6 is added with LM simultaneously to improve the lubrication properties of lithium grease, and expand the application scope of LM.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0017/

Investigating the tribological properties of TiO2 nanoparticles added Thevetia peruviana and Cucurbita pepo L. blend oils

The paper studies the lubricant properties of blends of Thevetia peruviana oil (TPO) and Cucurbita pepo L. oil (CPO) prepared at different proportions. The physicochemical properties were determined as per ASTM standard and the anti-wear and extreme pressure tests were performed using four-ball tribotester as per ASTM D4172–94 and ASTM D2783, respectively. The blend of 40% TPO and 60% CPO was found the best blend as per the Entropy-TOPSIS method and further at optimal concentration of 1 wt% of titanium oxide nanoparticles it exhibited the coefficient of friction of 0.0329 ±0.002 and wear scar diameter of 0.291 ± 0.005 mm. The present study indicates that TPO-CPO blends with optimal additivation can be an alternative biodegradable solution to commercial mineral oils.

Preparation and tribologic properties of Ti and Zr nitride multilayer coatings

This paper focuses on synthesis and characterization of Zr/Ti and Ti/Zr nitride multilayer coatings by magnetron plasma sputtering to enhance the tribologic properties. The synthesis of nitrides was achieved by non-reactive deposition using Ti or Zr nitride targets or by reactive deposition using Ti or Zr targets in the presence of nitrogen. The formation of nitride layers was highlighted by XRD, EDX and XPS investigations, while the tribologic properties were made with HFRR equipment. The tribological study showed that the coefficient of friction and wear scar diameter decrease in multilayer films with zirconium nitride as the upper layer.

Synergistic Effect of Acrylate of Dialkyl Dithiophosphoric Acid Combined with Molybdenum Dialkyl Dithiocarbamate as Additives in Gear Oil

With the aim of improving the tribological properties of low-viscosity gear oil for automobiles, an acrylate of dialkyl dithiophosphoric acid (ADDP) with strong polar groups was synthesized. The tribological behavior of ADDP combined with molybdenum dialkyl dithiocarbamate (MoDTC) in gear oil was systematically studied. Tribological performances of gear oil containing different additives were assessed using a four-ball friction and wear tester. The obtained tribological characteristics reveal that ADDP and MoDTC can significantly improve the antiwear and antifriction performance of low-viscosity gear oil. Moreover, compared with using MoDTC or ADDP alone, the average friction coefficient and wear scar diameter of ADDP combined with MoDTC further decreased by 2.41–19.15% and 5.00–18.19%, respectively. Analysis of the worn surface showed that the structural characteristics and physical synergistic lubricating actions of the ADDP with MoDTC additives during the friction process can contribute to the exceptional tribological properties of the hybrid additives.

Performance evaluation of trimethylolpropane ester as high-temperature resistant lubricant for high performance water-based drilling fluids

As drilling operations increasingly target large-displacement wells, horizontal wells, deep wells, and ultra-deep wells, the challenges of excessive drilling resistance and downhole safety have become more prominent. During the drilling process, one of the primary technical methods for preventing and addressing drilling safety issues is the reduction of downhole frictional resistance through the addition of lubricants to the drilling fluid. In this study, a high-temperature and high-salt-resistant drilling fluid lubricant was synthesized using raw materials such as oleic acid and trimethylolpropane. The lubricant exhibited excellent lubrication performance under high-temperature and high-salt conditions. When added at a 1.5% dosage to a 4% freshwater-based slurry, HZ-1 resulted in a 95.2% reduction in the lubrication coefficient. After aging at 200 °C, the HZ-1-containing slurry maintained an 87.9% reduction, and when used with a NaCl dosage of 36%, the slurry still exhibited an 80.5% reduction. Furthermore, HZ-1 exhibited favorable compatibility with both polymer drilling fluid and polysulfone drilling fluid systems. It had basically no effect on the rheological properties of the drilling fluid and reduced filtration loss. Moreover, HZ-1 exhibited a lubrication coefficient reduction rate of 94.5% in freshwater-based slurry and 85.5% in brine-based slurry, outperforming domestic and foreign lubricants. It outperformed these comparative lubricants in terms of lubrication and drag reduction within the same period. The analysis of the lubrication and drag-reduction mechanism revealed that HZ-1, when adsorbed onto a metal surface, formed a hydrophobic and high-strength physical adsorption film. This film prevented direct contact between drilling tools and the friction surface of the well wall, resulting in a significant reduction in the lubrication coefficient. Furthermore, using the drilling fluid system containing HZ-1 lubricant, the wear scar diameter formed on the surface of the four-ball friction experimental body was the smallest, measuring only 0.78 mm. This property significantly enhances the extreme-pressure and anti-wear performance of the friction sub-surface. Consequently, HZ-1 effectively prevents complications such as pressure support, stuck drilling, and high frictional resistance, thereby significantly reducing costs and improving efficiency.

Tribological characteristics and mechanisms of boronitrogenated methyl epoxyoleate as bio‐based additive in petroleum lubricant

In this work, boronitrogenated methyl epoxyoleate (BNMEO) was prepared by boronization and nitrogenation of methyl epoxyoleate (MEO). The tribological properties of BNMEO and MEO as bio‐based lubricating additives in a petroleum oil were determined on a four‐ball tribometer. The topographies, element compositions, and tribochemical species of the worn surfaces were analyzed by a scanning electron microscope, an energy dispersive X‐ray spectrometer, and an X‐ray photoelectron spectroscope, respectively. Results showed that both BNMEO and MEO, especially the former, were excellent in fortifying load‐carrying capacities and friction‐reducing and antiwear abilities of the oil under mild loads. However, their abilities in improving extreme pressure property of the oil under severe loads were very limited. The prominent ability of BNMEO in reducing friction and wear was characterized by well‐increased maximum nonseizure loads and decreased wear scar diameters and friction coefficients and was attributed to generation of a dense and robust boundary lubrication film which consisted of a matrix of BNMEO with inclusions of aminic compounds, boron oxide, iron oxide, and hydrocarbons, thanks to strong adsorptions and tribo‐oxidations of BNMEO on the metallic surfaces in the tribological processes.

Friction Characteristics and Lubrication Properties of Spherical Hinge Structure of Swivel Bridge

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation.

Synthesis of long straight‐chain alkane substituted ferrocene with ultra‐robust oil solubility as multifunctional organometallic additive

Tailoring of organometallics structure toward desirable properties continues to be both fascinating and challenging in the field of materials science. Herein, a novel ferrocene derivative with long straight‐chain alkane mono‐substituent is synthesized and used as multifunctional organometallic additive in the base oil. This ferrocene‐based organometallic compound (MFc) is synthesized via the Friedel‐Crafts acylation of ferrocene with myristyl chloride, followed by reduction with sodium borohydride. The chemical structure, crystallizability, surface morphology, and the thermal properties of the as‐synthesized compound are systematically characterized. As the iron‐containing standard substance, the MFc was preferable dissolve in lubricating oil with the iron element content as high as 2*105 ppm. Resultantly, the MFc/oil solutions exhibited excellent stability even after high‐speed centrifugal treatment, long‐term storage up to 3 months, and ultra‐low temperature treatment at −40°C for 24 h. Moreover, the MFc as a functional lubricant additive could reduce the average wear scar diameter, wear volume, and coefficient of friction with 40%, 73%, and 18%, respectively, as compared to the corresponding pure base oil. This synthetic strategy provides a novel perspective for the design of functional organometallics, and the as‐synthesized novel ferrocene derivative may find a wide range of advanced potential applications in analytical chemistry, tribology, and interfacial science.

Investigation of tribological behavior of MOFs/g-C3N4 nanocomposite for insight into effect of flake-on-sheet and ball-on-sheet nanostructure

Herein, we designed two catalogs of metal organic frame materials (MOF)/carbon nitride(g-C3N4) composite nanostructures (flake-on-sheet and ball-on-sheet nanostructure appearances) to probe the effect of composite nanostructures on the cooperative friction mechanism. The tribological behaviors of MOF/g-C3N4 composite nanostructures were extensively investigated in base oil on the four-ball friction tester. The results showed that the anti-wear ability of flake-on-sheet shaped MOF/g-C3N4 in oil was superior to the ball-on-sheet shaped MOF/g-C3N4, whereas the anti-friction and load-bearing ability of latter was preferable to the former. The flake-on-sheet shaped MOF/g-C3N4 enabled the friction coefficient (COF) and wear scar diameter (WSD) of oil to reduce 31.90% and 45.46%, while the ball-on-sheet shaped MOF/g-C3N4 enabled the friction coefficient (COF) and wear scar diameter (WSD) of oil to decrease 37.07% and 42.15%, respectively. Due to the morphology difference, the anti-frition and anti-wear mechanism of the flake-on-sheet shaped MOF/g-C3N4 were reliable to the tribo-film consisting of adsorption film and tribochemical film, whereas that of ball-on-sheet shaped MOF/g-C3N4 depended on the synergistic effect of the tribo-film and the ball bearing effect of MOF nanospehere in composite structure. Moreover, the interface interaction in composite structure also had a underlying influence in the friction behavior of nanoadditive.

Enhancing the Elastohydrodynamic Lubrication and Vibration Behavior of Rolling Bearings Using a Hybrid Bio-Grease Blended with Activated Carbon Nanoparticles

In recent years, bio-lubricants have received a growing interest for industrial applications. Still, a full-scale implementation in machinery lubrication requires a thorough evaluation of their performance through tribological and operational tests to stand upon their performance. Additionally, the promising outcomes achieved by nanoadditives in improving the performance of synthetic lubricants have prompted research efforts to identify suitable nanoadditives for bio-grease. This paper introduces a bio-grease from a hybrid vegetable oil and glycerol monostearate as a thickener for the lubrication of rolling bearings. Activated carbon nanoparticles (ACNPs) as nanoadditives were synthesized, characterized, and incorporated into the bio-grease at concentrations of 0.5, 1, and 2% by weight. Tribo-tests were conducted on these bio-grease blends, and running tests were carried out using 6006 ball bearings on a custom test rig. Throughout a 30-min test run under a radial load of 10% of the bearing’s dynamic load rating, mechanical vibrations and power consumption were measured and analyzed for each bearing. The bio-grease with ACNPs exhibited a substantial reduction in wear scar diameter (WSD) and coefficient of friction (COF), achieving improvements of up to 73.6 and 65%, respectively, in comparison to lithium grease. Furthermore, the load carrying capacity was enhanced by 200%. The study revealed a strong correlation between measured vibration amplitudes and the viscosity of the bio-grease. The absence of high frequency resonant bands in vibration spectra indicated that the test grease samples satisfied the conditions of elastohydrodynamic lubrication, and these findings were corroborated through calculations of the minimum oil film thickness.

Anti-friction and Wear Resistance Performance of Palm Olein Grease with Molybdenum Disulfide Additive

In this study, palm olein-based grease with a micro-molybdenum disulfide (MoS2) additive has been developed. The grease was prepared using various MoS2 concentrations to investigate the role of additives in improving grease performance. A four-ball tribological test was conducted to investigate the surface morphology, wear depth, and volume loss of the steel ball. The results indicated that the MoS2 additive reduced the coefficient of friction and wear scar diameter compared to pure palm olein grease. The value of 0.5 wt.% was considered the optimum value, reflecting the best grease performance indicated by low friction coefficient, wear diameter, wear depth, and volume loss. Elemental analysis revealed that the MoS2 additive was deposited onto the wear tracks, improving the surface protection. Thus, this additive was found to have a good potential for improving palm olein-based grease.

Study on the tribological and rheological properties of magnetorheological fluids based on different base oils

Abstract Base oil has great influence on the tribological and rheological properties of magnetorheological fluid. In this paper, four types of magnetorheological fluid are prepared respectively by silicone oil, mineral oil, synthetic oil (PAO) and castor oil, and their tribological and rheological properties are investigated. Firstly, the viscosity of the magnetorheological fluid is measured by a viscometer. Then the friction coefficient and wear scar diameter of the magnetorheological fluid is measured by a four ball friction testing machine. Next, the sedimentation rate of the magnetorheological fluids is calculated by the observation method. Finally, the shear yield stress of the magnetorheological fluid is measured by a rheometer. By analyzing the experimental data, it is concluded that the magnetorheological fluid prepared by white mineral oil and castor oil has excellent wear resistance. The magnetorheological fluid prepared by castor oil has better sedimentation stability and higher shear yield stress. Consequently, the magnetorheological fluid prepared by castor oil has better comprehensive properties.

Formulation and evaluation of bio-grease from the blend of chemically modified rice bran oil and Calophyllum inophyllum oil

Vegetable oils are a highly promising alternative to produce various lubricants, owing to their biodegradability and eco-friendliness. In comparison to mineral oil, these oils possess a higher flash point and viscosity index, along with superior lubricating properties. Additionally, most of the vegetable oils are easily accessible in local markets in India. However, their industrial application is limited by poor thermal and oxidative stability, which can be addressed through chemical modification, the addition of appropriate additives, or by blending these oils. Greases, characterized by their semi-solid consistency, are widely used lubricants. Most of the grease production is based on mineral oils as base oil and lithium soap as a thickener. These materials are not only non-biodegradable but also scarce and have health implications. Consequently, biodegradable grease represents an eco-friendly and healthy alternative. Grease made using vegetable oils with the required properties has the potential to bring about revolutionary changes. The present work focuses on the feasibility of using chemically modified blended rice bran oil (RBO) and Calophyllum inophyllum oil (CIO) as a bio-lubricant. The oils undergo a two-step modification process, involving a transesterification reaction followed by epoxidation. Significant improvements have been observed in the chemical properties (acid, peroxide, and iodine values) of transesterified epoxidized rice bran oil Calophyllum inophyllum oil mixture–50:50 (ETRCIO) when compared with Unmodified Rice bran oil Calophyllum inophyllum oil mixture–50:50 (RCIO). The acid value, peroxide value, and iodine value improved by 91.66%, 87.08%, and 15.78% respectively. The rheological, tribological, and chemical properties of the blended samples have been evaluated and compared to pure oils using American Society for Testing and Materials (ASTM) and Indian Standards (IS). Additionally, ETRCIO was used to develop a bio-grease, and its tribological properties were extensively analyzed. The mean coefficient of friction (COF) and wear scar diameter (WSD) of the ETRCIO grease sample improved by 10.20% and 29.32% respectively when compared with that of commercially available grease. These findings indicate that the ETRCIO bio-grease exhibits superior tribological properties in comparison to commercially available grease.

Preparing vegetable oils-based metalworking fluids by a hydrolysis-esterification two-step process

Oil-soluble esters of free fatty acids were synthesized with a 2-step process including the first step of reacting vegetable oil with water in the presence of sulfuric acid and p-Toluenesulfonic acid as a catalyst, followed by removing water and glycerol, and the second step of reacting the obtained free fatty acids with various polyhydric and fatty alcohols. The best conditions were 190 °C, 6 h, 30 to 1 water to oil molar ratio, 5 wt% PTSA catalyst loading in the hydrolysis reaction (the 1st step), and 150 °C, 10 h, 4 to 1 fatty acid to trimethylolpropane molar ratio, 1 wt% PTSA catalyst loading in the esterification reaction (the 2nd step). Under the best conditions, the process achieved the final product with the 87% yield of free fatty acid trimethylolpropane ester and 82% conversion of free fatty acid. Different esters were made concurring to the aforementioned conditions with distinctive polyhydric and fatty alcohols. Hydrolysis reactions facilitated by catalysts offer an alternative approach to traditional hydrolysis in supercritical conditions, enabling efficient substrate conversion under milder operating conditions. Furthermore, the inclusion of the obtained esters mixed with base oil and additives produced bio-based metalworking fluids with exceptionally lubricant performance in wear resistance, with a wear scar diameter of 0.33 mm.

A Review on the Impact of Bio-Additives on Tribological Behavior of Diesel Fuels

Automobile engines require lubrication to lessen the impact of friction due to the high levels of wear and frictional heat generated by the sliding parts. Wear and friction will cause engine parts to endure for less time, be less reliable, and require more maintenance. Diesel fuel can potentially be replaced with biodiesel among other fuels. Diesel engines have a serious problem with equipment that is lubricated by the fuel itself. This study’s goal is to assess the influence of bio-additives on the diesel fuel tribological behavior and energy balance during the car’s idle running, acceleration, constant speed, and braking. Lubricity issues with reformulated diesel and lubricity test procedures are explained. The relationship between tribology and bio-additives is also briefly illustrated. According to the literature, adding bio-additives to fuel boosts its lubricity. Biodiesel has long been considered an additive with excellent lubricant properties. Even in small amounts, adding biodiesel to diesel fuel can increase its lubricity without the need for conventional lubricity additives. This is especially true for diesel fuel with ultralow sulfur. Diesel fuel characteristics determine the precise blending percentage needed to provide the proper lubricity of maximum 520 μm testing wear scars with a high-frequency reciprocating rig (HFRR), although 2% biodiesel nearly invariably imparts adequate lubricity to biodiesel blends. Tall oil fatty acid (TOFA) was one of the bio-additives investigated by HFRR. When the additive concentration was raised from 0 to 500 g/g, the wear scar diameter (WSD) of nonadditive diesel fuel was lowered by 60.3%, from 630 to 250 μm, and the coefficient of friction (COF) was lowered by 95.7%, from 0.47 to 0.02.

Investigation of Tribological Properties of Mahua Oil Mixed with Zinc Oxide Nanoparticles

In today’s paradigm petroleum and petro-based chemical products are being extracted and consumed at a substantial rate, proving to be hazardous and detrimental to the earth. Bio based resources are environmentally friendly, energy efficient, economical, and proved to be an alternative to the present mineral oils. This paper documents the research on naturally available mahua seed oil for bio-lubrication, its flash point and fire point, tribological properties namely coefficient of friction and wear scar diameter have been modified by the addition of zinc oxide (ZnO) nanoparticles in different concentrations by weight percentage (0.25, 0.50, 0.75, and 1.0). four-ball tester was used according to ASTMD-4172 standards (60 min under 40 kg running at 1200 rpm). Probe ultrasonicator was used for particle dispersion. It was found that 0.75 wt. % loading of ZnO in mahua oil resulted in a 57.14% drop of coefficient of friction, but a slight increase in the wear scar diameter of 30.60% was observed.

Comparison of conventional hydrothermal and microwave‐assisted synthesized g‐C3N4/MoS2 nanocomposite coated steel substrate by tribological measurement

AbstractMolybdenum disulfide is an effective solid lubricant, but it suffers from oxidation and moisture absorption issues, resulting in insufficient wear resistance and a shortened lifespan. This study introduces an innovative approach, integrating graphitic carbon nitride with molybdenum disulfide via advanced microwave‐assisted synthesis, offering precise control over synthesis parameters. The research assesses the tribological performance, comparing it with conventional hydrothermal synthesis. The study extensively investigates the morphology, microstructure, and tribology of a g‐C3N4/MoS2 nanocomposite created through novel microwave (g‐C3N4/MoS2‐MW) and hydrothermal techniques (g‐C3N4/MoS2‐HT). MoS2 exhibits a flower‐like structure, while graphitic carbon nitride has a layered structure, as confirmed by elemental analysis via energy‐dispersive X‐ray spectroscopy. X‐ray diffraction identifies g‐C3N4 peaks at 13.0° (100) and 27.5° (002) and hexagonal MoS2 peaks at 14° (002), 32.7° (100), 35.8° (102), and 58.3° (110). The Fourier‐transform infrared spectrum reveals peaks at 1237.4 and 808 cm−1 (aromatic and triazine ring breathing modes in g‐C3N4), 1407.1 and 1638.9 cm−1 (C=N and C−C heterocyclic structures), and 3432 cm−1 (vibrations due to −NH and −OH). The coefficients of friction for microwave‐assisted and traditional hydrothermal synthesized nanocomposites are 0.22 and 0.34, respectively. The wear depths are 98 microns and 141 microns, with a wear scar diameter of 2.87 mm for g‐C3N4/MoS2‐MW and 3.45 mm for g‐C3N4/MoS2‐HT, indicating superior lubrication with the microwave‐assisted coating.

Excellent corrosion inhibition and lubrication performance of MMT based ionic liquids as ester oil additives

In this work, electrochemical experiments and friction tests were conducted to investigate anti-corrosion properties and lubrication performance of the 2-mercapto-5-methyl thiadiazole (MMT) based ILs as additives of ester oil. The outcomes of electrochemical experiments were further supported by quantum chemical simulation which clarified the reason for corrosion inhibition from a microscopic perspective. Electrochemical impedance spectroscopy obtained from different temperatures (from 293 K to 323 K) showed that the inhibitors could reach a higher corrosion inhibition efficiency at 293 K. The experimental data exhibited that the adsorption behavior obeys Langmuir adsorption isotherm and the inhibitors adsorbed on the surface in a laying way seen from the results of theoretical simulation. Besides, SEM and XPS were employed to analyze the corrosion morphologies of immersion tests corroborating the presence of adsorption film on the steel surface. The tribological performance of MMT based ILs as base oil additives were examined by four-ball tester. The friction coefficient dropped by 47% and wear scar diameter decreased by 28% contrast to the base oil sample. The outstanding corrosion inhibition properties and friction-reducing and anti-wear performance could make it prospect for some industrial applications in energy saving.

Wear pressure induced structural changes of OLC nanoparticles and their regulated lubrication performances by mixing with NDs and GO

Here we report the tribological properties of nanosized onion-like carbon (OLC), OLC-nanodiamond (ND), and OLC-graphene oxide (GO) as additives in lubricant oil tested under different wear pressure. Under the wear pressure of 588 N of the four-ball testing, the 0.125 wt% addition OLC reduced the wear volume and the wear scar diameter by 36.29 % and 82.42 %. TEM characterization revealed structural changes in contour of the OLC particles after the wear testing. Pressure-induced agglomeration was seen for the OLC nanospheres, and the squeezed lattice changes resulted in formation of sp3 diamond structure inside the spheres. These structural changes are directly related to the loading force. However, addition of the sp3 NDs and sp2 GO deteriorated the lubricating performances of the OLC-added lubricant oil.

Tribological Properties of h-BN, Ag and MgO Nanostructures as Lubricant Additives in Vegetable Oils

There exists an ever-growing need for sustainable engineering solutions to improve emission control and the energy efficiency of tribosystems. This study examines the tribological properties of two environmentally friendly vegetable fluids, soybean and sunflower oil, with the addition of three non-toxic nanostructures (h-BN, silver and MgO) at different concentrations. It was found that nanostructures added to vegetable oils at specific concentrations can exhibit good friction reduction and wear preventive properties. The addition of h-BN nanosheets in sunflower oil decreased the coefficient of friction and the wear damage, as measured by the wear scar diameter. Silver and magnesium oxide nanoparticles further reduced the friction and wear, respectively. In addition to the tribological testing of the samples, investigations were performed using an optical microscope, SEM and EDX to elucidate the mechanisms that may have led to the observed friction reduction and wear-preventive properties of different nanostructure additives. The thermophysical properties of the samples were also measured. It was found that the thermal conductivity of both base oils could be enhanced by 24% when using h-BN at 0.25 wt% concentration.