Four-ball Tester Research Articles

Evaluation of tribological properties of vegetable oil–based ionanolubricants: An experimental study

Growing environment concern has forced us for the development of environmentally acceptable lubricants. In this study, tribological properties of sesame oil and castor oil containing imidazolium-based ionic liquid 1-ethyl 3methylimidazolium dicyanamide ([EMIM][DCN]) (IL1), phosphonium-based ionic liquid Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ([P66614][BTMPP]) (IL2) and titanium oxide (TiO2) nanoparticles (NPs) as hybrid additives have been investigated using four-ball tester with ASTM D4172B. Three different concentrations of IL1, IL2 and TiO2 NPs were selected for the formulation of vegetable oil–based ionanolubricants. It was found that castor oil with the addition of 0.03[Formula: see text] of TiO2 NPs and 1.3 vol.% of IL1 shows the lowest specific wear rate amongst all investigated lubricant samples. It is evident from field emission scanning electron microscopy analysis of worn-out surfaces of steel balls that a combination of ball bearing effect and tribofilm formation is responsible for the improved tribological characteristics.

Tribological evaluation of PEG-based nanolubricants modified with graphene and copper oxide

Nanolubricants are dispersions of nanomaterials in a lubricating base. In this work, polyethylene glycol (PEG) was modified with graphene (G) and copper oxide (CuO) to obtain a nanolubricant (NL). The nanolubricants were prepared and their physicochemical and tribological properties were evaluated. The base and the nanomaterials were evaluated using Fourier-transform infrared spectrometry (FTIR), field-emission scanning electron microscopy coupled with energy dispersive spectroscopy (FE-SEM-EDS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Raman spectroscopy (Raman). Rheology and Tribology tests were also performed using a four-ball tester according to ASTM 2783. The results showed that nanolubricants have a Newtonian behavior and the viscosity was not significantly modified with the additives. The weld point obtained for the nanolubricants was 160 kgf. In addition, when compared to the PEG, the size of the wear scars was reduced by 9.6% (PEG with 0.01% w/w of CuO) and 35.3% (PEG with 0.05% w/w of CuO and G). The wear protection provided by G is higher than the protection provided by CuO. When the two additives were added, the wear protection increased, and a synergistic effect was observed. Two protection mechanisms were observed in the SEM: rolling bearing/ball effect (CuO) and deposition of G at valleys and peaks of the surface roughness. This article shows novel results related to a laboratory evaluation of nanolubricants in a typical tribological test (four-ball). A novel result was observed in the synergistic effect between the two additives (graphene and CuO) determined by the wear mechanism observed in the tests.

Effect of polymer additives on the tribological performance of soybean oil

PurposeThis study aims to investigate the behavior of vegetable oil with two additives. Base oil’s tribological qualities can be improved with the help of several additions. In the present investigation, soybean oil is served as the foundational oil due to its eco-friendliness and status as a vegetable oil with two additives, named polytetrafluoroethylene (PTFE) and molybdenum disulfide (MoS2).Design/methodology/approachAs additives, PTFE and MoS2 are used; PTFE is renowned for its anti-friction (AF) properties, while MoS2 is a solid lubricant with anti-wear (AW) properties. This investigation examines the synergistic impact of AF and AW additions in vegetable oil. The lubricity of the base oil is measured by using a four-ball tester, and the wear properties of the oil at different additive amounts are determined by using a universal tribometer.FindingsPTFE (at 5 Wt.%) and MoS2 (at 1 Wt.%) were found to improve the tribological performance of the base oil. The weld load is significantly increased when 5 Wt.% of PTFE + MoS2 is added to the base oil.Originality/valueA better tribological characteristic can be achieved by combining additives that amount to less than 1% of the base oil. In experiments with highly concentrated MoS2, the adequate pressure improved dramatically, but the lubricant’s tribological characteristics did not.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0321/

Preparation and tribological properties of Phenyl-Functionalized thermally reduced GrapheneOxide

We report a two-step method for preparing hydrophobic graphene. This method transforms graphite oxide (GO) into thermally reduced graphene oxide (TRGO) and then into phenyl-functionalized thermally reduced graphene oxide (PTRGO) through high-temperature thermal reduction and a heat-induced solid-phase chemical reaction. GO was successfully stripped, and TRGO was prepared by high-temperature thermal reduction. The phenyl radicals produced by the thermal decomposition of benzoyl peroxide(BPO) preferentially induced the ring-opening of the epoxy group on the TRGO, and the phenyl groups were attached. The prepared PTRGO displayed excellent hydrophobic properties, with a water contact angle of 132.0°, and was stably dispersed in the base oil without requiring any surfactants or modifiers. Four-ball testing showed that when the additive amount of PTRGO was 75 mg/L, the coefficient of friction (COF) and wear scratch diameter (WSD) of Abu Dhabi (AD) base oil (150 N) decreased by 24.2% and 15.7%, respectively.

Synergistic lubricating behaviors of Zn-MOF/[P88814]DEHP composite used as lubricating oil additive

Use of the synergistic effect between nanomaterials and ionic liquids is of great significance for designing high-performance lubricating materials. In this work, Zn-MOF/[P88814]DEHP (zinc complexes with 2-aminoterephthalic acid nanosheets/trioctyltetradecylphosphonium bis (2-ethylhexyl) phosphate) composites were successfully synthesized by grinding the mixture of [P88814]DEHP and Zn-MOF with different mass ratios and evaluated as a new kind of the white oil additive using a four-ball testing machine. Results demonstrate that the optimal mass ratio of Zn-MOF to [P88814]DEHP was 1:1 and the Zn-MOF/[P88814]DEHP composite with 2.0 wt% addition amount into the white oil significantly reduced friction coefficient and wear. Such obvious friction-reducing and outstanding anti-wear properties of Zn-MOF/[P88814]DEHP composite could be attributed to the synergistic lubrication between Zn-MOF and [P88814]DEHP. This work investigated the synergistic lubrication between MOFs and ILs, which provided a new idea for designing and preparing new lubricating oil additives.

Tribological Behavior and Wear Protection Ability of Graphene Additives in Synthetic Hydrocarbon Base Stocks

Graphene carbon materials show good tribological properties due to their unique layered structures. In this work, the tribological properties of graphene (GN) and fluorinated graphene (FGN) were studied in two kinds of synthetic hydrocarbon base stocks at different working conditions. Firstly, the structures of GN and FGN were characterized comparatively using FT-IR, Raman, XRD, and TGA. Secondly, the tribological properties of GN and FGN as the lubrication additives both in PAO6 and CTL6 were studied on a four-ball tester. Finally, the surfaces of friction counterparts, before and after tribological tests, were analyzed to disclose the lubrication mechanism using UV, micro-Raman, and EDS. The results show that GN and FGN can be stably dispersed in the selected synthetic hydrocarbon base stocks with 1 wt.% T161 as the dispersant, and the optimal addition of graphene additive is 100 ppm, which shows better friction reducing and anti-wear properties. GN and FGN also show better tribological performance at a higher load (not less than 392 N), and their compatibility with PAO6 is better. The worn surface analysis shows that the graphene additive participates in the lubrication film formation during friction by frictional chemical reaction with friction counterparts, which could improve the stability and tribological performance, resulting in an increased application temperature of synthetic hydrocarbon base stock by at least 10 °C.

‘Triangle Ester’ Molecules as Blending Components in Mineral Oil: A Theoretical and Experimental Investigation

The present work explored the use of fatty acid ‘Triangle ester’ molecules (Epoxidized Ester (EE), and Thiirane Ester (TE)) as antifriction and antiwear additives at varying levels for Group I and Group II mineral base oils using the standard ASTMD-4172B four-ball test. Relative to neat base oil, EE blends showed improved antifriction by ~61% and ~42% and antiwear properties by ~32% and ~41% in Group I and Group II base oils, respectively, while the TE blends showed friction reduction by ~65% and ~40% and wear reduction by ~93% and ~50% relative to the same neat base stock. Time evolution of the ‘Triangle ester’ molecules and their blends with mineral oil (modeled as hexadecane) w.r.t. conformational changes, adsorption energy, intermolecular energy, and effect of the applied stress were estimated theoretically using MD simulations. Further, optimized levels of these additives were explored for their effectiveness as a blending component for commercial engine oil (CEO) and could reduce the friction and wear of CEO by ~50% and ~30%, respectively.

Effect of Saturated Fatty Acids on the Antiwear and Rheological Properties of Olive Oil

The study determines the effect of saturated fatty acids (coconut oil) on the rheological and tribological properties of olive oil. The olive oil is blended with different proportions of coconut oil (10%, 20%, 30%, 40%, and 50%) and the different properties (flow behaviour and antiwear) are studied on Anton Paars rheometer and Four-ball tester respectively. The study reveals that the blends depict Newtonian behaviour with a decrease in the dynamic viscosity of the olive oil. Also, WSD decreases at a higher proportion of coconut oil in the blends with an improvement of 10.74% at a 50:50 ratio. The blending of two oils for the enhancement of the lubrication properties of biolubricants can prove beneficial in making them a suitable replacement for mineral oils.

Electrified four-ball testing – A potential alternative for assessing lubricants (E-fluids) for electric vehicles

The increasing worldwide demand for hybrid and electric vehicle technology has brought new challenges for the global lubricant industry. The new lubricants for electric vehicles, also called E-fluids or EV-fluids, are expected to meet a new set of requirements including withstanding the much severe operating conditions of EV powertrains. High starting torques, high RPMs and uncontrollable shaft currents passing through the contact interfaces are some of the most challenging powertrain conditions that can impact the performance of these lubricants. Although there have been some papers already reporting on significant alteration of tribological properties of lubricants under electrification, so far there are no standard test protocols aimed at the fast and reliable screening of base oils, additives and formulated lubricants under such conditions. Thus, this research work focuses on exploring the popular four-ball ASTM-D4172 standard method to evaluate the tribological behavior of lubricants under electrified conditions. Specifically, a conventional four-ball tester was instrumented with a DC power source and a resistance data logger was used to explore the friction and wear performance of various lubricants (including a neat base oil, two automatic transmission fluids (ATF-3 and ATF-5) and a gear oil) with different dielectric strength under the conditions of ASTM-D4172 standard with and without DC currents (0, 1.5 and 3 A). The changes in average wear scar diameter, specific wear modes and mechanisms, friction coefficients, electrical contact resistance and temperature were analyzed and reported. Besides, the chemical changes in oils during the electrified tests were evaluated via IR spectroscopy. The main findings suggest that passing current through the four-ball contact interfaces significantly alters friction, wear and temperature in comparison to the conventional standard method without electrification. Thus, the proposed test method with electrification could be a potential new alternative for testing E-fluids under electrical environments.

Synthesis and Frictional Characteristics of Bio-Based Lubricants Obtained from Fatty Acids of Castor Oil

The depletion of oil reserves and concerns about the environmental impact of the use and incorrect disposal of mineral lubricants have been promoting the development of bio-based lubricants. In this study, biolubricants obtained from fatty acids of castor oil were synthesized by esterification (>wt.%93), epoxidation (>wt.%92), and oxirane ring opening reactions using water (>wt.%92) or 2-ethylhexanol (>wt.%94) as nucleophilic agents. The frictional characteristics of the synthesized samples were obtained through tribological tests performed in a four-ball tester and compared with a commercial mineral oil. The sample obtained through oxirane ring opening with water showed the best frictional performance (FC = 0.0699 ± 0.0007) among the prepared samples, with equivalent wear rate (WSD = 281.2 ± 5.54 μm) and ca. 20% lower friction coefficient when compared to the commercial mineral oil, indicating its great potential for replacing mineral fossil oils.

Improvement of tribo-active behavior of g-C3N4 nanosheets using m-LaVO4 nanoparticles

The tribological properties of the graphitic carbon nitride (g-C3N4) nanosheets are far better than morphologically similar reduced graphene oxide. Further improvement of the tribological behavior of g-C3N4 nanosheet was intended by introducing lanthanum orthovanadate nanoparticles in the monoclinic phase (m-LaVO4). The HR-SEM and TEM/HR-TEM of the binary nanocomposite (g-C3N4/m-LaVO4) displayed dispersed m-LaVO4 nanoparticles throughout g-C3N4 nanosheets. The synthesized nano additives, nanosheets (g-C3N4), nanoparticles (m-LaVO4), and nanocomposite (g-C3N4/m-LaVO4) could be characterized using p-XRD and FT-IR. XPS analysis of the nanocomposite helped to determine the chemical states of elements. Tribological tests were carried out on a four-ball tester using ASTM D4172 and ASTM D5183 test conditions at 0.05 % w/v optimized concentration of the additives in paraffin oil (PO), which is 4–5 times lower than the available literature reports regarding nanocomposites of g-C3N4 nanosheets. The results revealed a significant decrease in friction/wear and a remarkable improvement in the load-bearing capacity of the nanocomposite as compared to g-C3N4 nanosheets and m-LaVO4 nanoparticles. The morphological examination of the worn steel surface through AFM and SEM supported the observed tribological data. EDX analysis of the tribofilm verified the elemental composition, whereas the XPS yielded the chemical states of the constituent elements. The highly advanced tribological activity of the nanocomposite has been ascribed to the synergy between noncovalently interacting nanoparticles (m-LaVO4) and nanosheets (g-C3N4). The possible lubrication mechanism has also been depicted.

Preparation and Modification of Graphite-based and Coal-based Graphene and its Tribological Properties in Lubricants

Graphite-based graphene oxide (GO) and coal-based graphene oxide (GO/SiO2, which we call graphene oxide/SiO2 because the surface of the resulting coal-based GO is linked with SiO2 from the coal structure) were prepared by the conventional Hummers oxidation method and ultrasound-assisted Hummers oxidation method, respectively, using natural graphite powder and Xinjiang Wucaiwan coal as carbon sources. Furthermore, the structures of the two were studied comparatively. Afterwards, the two lamellar structure products were hydrophilically modified with octadecylamine and dicyclohexylcarbodiimide by a hydrothermal method. And then, added these products (graphite-based GO-ODA and coal-based GO/SiO2-ODA) to No.32 cycloalkyl base oils in order to comparatively investigated their tribological properties as lubricant additives. The results showed that the dispersion stability of coal-based GO/SiO2 in the lubricant was significantly better than that of graphite-based GO; meanwhile, the tribological performance of GO/SiO2-ODA in the lubricant better than that of graphite-based GO-ODA due to the surface linkage of coal-based GO/SiO2 with SiO2 particles. After 1 h - long grinding in a four-ball friction test, the lubricant friction coefficient of 0.03 wt% coal-based GO/SiO2-ODA oil reached a minimum of 0.118, which reduced 58.1% compared to pure base oil and reduced 2.8 times compared to the counterpart using graphite-based GO-ODA under the same experimental conditions.

Tribological performance of various blends of commercial SAE 40 oil and novel apricot oil-based bio-lubricant using a four-ball tester tribometer

Tribological performance of various blends of commercial SAE 40 oil and novel apricot oil-based bio-lubricant using a four-ball tester tribometer

Tribological performance of various blends of commercial SAE 40 oil and novel apricot oil-based bio-lubricant using a four-ball tester tribometer

Tribological performance of various blends of commercial SAE 40 oil and novel apricot oil-based bio-lubricant using a four-ball tester tribometer

Study on synthesis of biodegradable polyurea grease using modified vegetable oil

Lubricants have been applied in numerous industrial fields, as they help reduce friction and heat generated when operating machines and also protect metallic parts in corrosive environments. In some applications, especially in marine, these greases need to be biodegradable, or they get accumulated and can be harmful to aquatic life. To address this matter, modified vegetable oil was used instead of persistent mineral oil. Also, in submerged conditions, polyurea grease outperforms traditional lithium grease as the latter is more susceptible to water washout. So, in this paper, the polyurea thickener was synthesized in-situ in biodegradable modified vegetable oil by using methylene diphenyl diisocyanate and amines as precursors. The fabricated grease chemical properties were determined by FTIR, and its tribological characteristics were studied by dropping point, penetration, and four-ball test. Results showed that polyurea grease has high operational temperature (dropping point at 278 oC), excellent pumpability (penetration 275 mm-1), and offers great wear resistance (wear load 233 kg).

Tribological and rheological properties of calcium grease with hybrid nano additives

Nanocomposite grease was created to reduce wear and friction on surfaces and enhance thermal conductivity. The tribological and rheological properties of nano grease were studied. Calcium grease with varied doses of hybrid TiO2/CNTs/GNs (0.5, 1, 2, 3 wt.%) was prepared. Transmission electron microscope (TEM) was applied to look at the microstructure of nano grease. Tribological and rheological properties of the nano grease were examined by using a four-ball tester. Wear scar diameter (WSD) was reduced by 30% at the optimal TiO2/CNTs/GNs concentration of 2% before beginning to rise. As TiO2/CNTs/GNs are applied in concentrations ranging from 0 to 2 wt.%, the friction coefficient of nano additive containing calcium grease steadily declines. At 2% concentration, the reduction in coefficient of friction was 45% about base grease. The friction coefficient was increased after that to 3 wt.%. Shear rate was reduced when the dose of TiO2/CNTs/GNs was increased. As the concentration of nanomaterials and shear rate increased, so did the viscosity of nano grease. Shear stress and apparent viscosity of the calcium grease containing 3% by weight of TiO2/CNTs/GNs are 43% higher than pure calcium grease, although they are still much lower than pure grease. The inclusion of the nanomaterial causes a roughly 19.5% increase in the dropping point of base grease. The thermal conductivity of nano grease is significantly improved by nano additives, increasing by around 130%, and the additives have a dramatic linear growth on the thermal conductivity of nano grease.

Artificial Intelligence-Based Rapid Design of Grease with Chemically Functionalized Graphene and Carbon Nanotubes as Lubrication Additives

Rapid chemical functionalization of additives and efficient determination of their optimum concentrations are important for designing high-performance lubricants, especially under multi-additive conditions. Herein, chemically functionalized graphene (FGR) and carbon nanotubes (FCNTs) were rapidly prepared by microwave-assisted ball milling and subsequently introduced into grease as additives. The tribological properties of the additives in grease at different concentrations and ratios were measured using a four-ball test. A reliable artificial neural network (ANN) model was established according to a few test results. Subsequently, the optimal concentration of multiple additives in the grease was predicted using a genetic algorithm and experimentally validated. The results indicated that the introduction of FGR (0.14 wt %) and FCNT (0.16 wt %) improved the antifriction and anti-wear performance of the base grease by 25.66 and 29.34%, respectively. The results of the ANN model analysis and friction interface characterization indicate that such performance is principally attributed to the synergistic lubrication of the FGR and FCNT.

Thermal and Tribological Properties Enhancement of PVE Lubricant Modified with SiO2 and TiO2 Nanoparticles Additive

The addition of nanoparticles may have a positive or negative impact on the thermal and tribological properties of base lubricant. The objective of this paper is to investigate the effect of nanoparticle dispersion in lubricant base in relation to its application in refrigeration system compressors. An investigation of tribological and thermal properties of nanolubricants for rolling piston rotary systems was carried out through four-ball tribology tests and thermal conductivity measurements. Nanolubricants dispersed with SiO2 and TiO2 nanoparticles were tested at various concentrations and temperatures. The changes in thermal conductivity and coefficient of friction (COF) were analyzed while wear weight loss was also calculated from wear scar size. A regression model of thermal conductivity enhancement was proposed for both types of nanoparticles. Zeta potential results show that nanolubricants have excellent stability. The thermal conductivity increases by the increment of nanoparticle concentration but decreases by temperature. The R-square for the regression model is more than 0.9952 with an average deviation not more than 0.29%. The COF for SiO2/PVE nanolubricant at 0.003 vol.% reduced 15% from the baseline. The COF for nanolubricants exceeds the result for base lubricants when the concentration is more than the threshold value. The optimum concentration of SiO2 and TiO2 nanoparticles improved the thermal and tribological properties of PVE lubricant and may offer an advantage when applied to refrigeration systems.

Analysis Performance of Modified Tamanu Oil Enhanced with Additives as Potential Green Alternative in Metalworking Fluids

Mineraloils have long been utilizedin industriesas machining lubricants, which contributed to theirdepletion and hick in priceandbeing non-biodegradable, harmful to the environment,and risk to health.Plant-basedoil is more biodegradable, renewable, and environmentally friendlyas a green alternative.However, in their crudestate, plant-based oilsare not up to par with the standard mineral oil used in lubricationin terms of high acidity, low-temperatureperformance,and oxidative instability.Further chemical modification and adding additives had to be made to improve the oil propertiesfor industrial applications.This study focused on the performance of transesterification of Tamanu plant-based oil with Trimethylolpropane (MTO) and Pentaerythritol (MTOP), which mixedwith 1% of Phosphonium Ionic Liquid (PIL) and 10% of Ammonium Ionic Liquid (AIL), producing a series of oil specimens; MTO, MTO+PIL1%, MTO+AIL%, MTOP, MTOP+PIL1%, and MTOP+AIL%.Thesesamplesare then subjected to physicalanalysis to determine the improvement of theirproperties intermsof kinematic viscosityand viscosityindexaswell as undergo a four-ball wear test to the determine the tribology aspects of the lubrication in terms of coefficient of frictions and wear scar diameter, in accordance withASTM standard method.All the results were compared with commercial MWF which synthetic ester (SE)as reference oil. The result of viscosity index revealsthat MTOP+PIL1% had the highest value of 178.76. MTO+AIL10% exhibits the lowest average COF(0.061) compared to other MTOs lubricants. Among MTOP, MTOP+PIL1%also had the lowest average COF which is 0.082. The addition of PIL1% to MTO and MTOP lowered the average scar diameter, 730.77μm and 674.93μmrespectively. With the enhanced properties from chemical modification and additives, Tamanu oil can be proposed as a green alternative fordevelopingthe metalworking fluid industries in the future.

Investigation of mixed hBN/Al2O3 nanoparticles as additives on grease performance in rolling bearing under limited lubricant supply

Grease plays an important role in reducing friction and wear of rolling bearings and improving their service life and reliability. However, increasing attention is being paid to the environmental pollution caused by discarded grease. In this paper, calcium sulfonate complex grease (CSCG) was prepared by using green raw materials, namely poly-alpha-olefin oil as the base oil and complex calcium sulfonate soap as thickener. In order to improve the lubrication and damping performance of the grease, hexagonal boron nitride (hBN) and nano-Al2O3, which have the potential to replace toxic additives, are mixed into the grease in different mass proportions. The thickener structure of each grease was characterized and analyzed. According to the bearing vibration and life of the two key performance indicators, four-ball tests and bearing vibration tests under limited lubricant supply (LLS) were performed. The results show that CSCG with 0.75 wt% hBN and 0.25 wt% Al2O3 (BN75AL25) has the best tribological and vibration suppression performance. The mean friction coefficient decreased by 11.3%, the wear scar diameter decreased by 6.1%, and the worn surface morphology improved significantly compared with CSCG. The frequency domain analysis showed that high, medium and low frequency vibrations were suppressed by 19%, 11.7% and 16.4%, respectively. In conclusion, BN75AL25 has the potential to become a green high-performance grease under LLS, which is worth further research and exploration.