Four-ball Tester Research Articles

Tuepras adding ISOALKY® alkylation technology to Turkish refineries

Lubricating grease is vital as a sealant and provides extra protection for automotive parts, such as bearings. Bearings are subjected to friction and sliding wear, which results in the degradation of automotive or machinery performance. The present article analysed the effect of molybdenum disulphide (MoS2) and butylated hydroxytoluene (BHT) as grease additives in reducing the frictional and wear behaviour of steel ball bearings. The experiment was conducted by preparing two formulated lithium complex-based grease with a different blending of additives of BHT only (LCG 01/18) and MoS2 + BHT (LCG 01/5). The formulated greases were compared with two industrial greases as the controlled parameters. Next, the physical characterization of formulated and industrial greases was conducted which includes dropping point test (ASTM D2265-00), cone penetration test (ASTM D217-02) and oil separation test (ASTM D6184-17). Then, the four-ball test (ASTM D2266-01) was performed to identify the effect of additives on the wear and frictional coefficient behaviour. The blending of MoS2 and BHT improves the physical characterization of grease in terms of dropping point and oil separation. The blending of MoS2 and BHT also helps to decrease the wear diameter and frictional coefficient. Nonetheless, further study is desired to gain a thorough understanding of the processes so that an optimal system can be developed for the industry.

Norner opens polymer centre to extend its plastics research

Lubricating grease is vital as a sealant and provides extra protection for automotive parts, such as bearings. Bearings are subjected to friction and sliding wear, which results in the degradation of automotive or machinery performance. The present article analysed the effect of molybdenum disulphide (MoS2) and butylated hydroxytoluene (BHT) as grease additives in reducing the frictional and wear behaviour of steel ball bearings. The experiment was conducted by preparing two formulated lithium complex-based grease with a different blending of additives of BHT only (LCG 01/18) and MoS2 + BHT (LCG 01/5). The formulated greases were compared with two industrial greases as the controlled parameters. Next, the physical characterization of formulated and industrial greases was conducted which includes dropping point test (ASTM D2265-00), cone penetration test (ASTM D217-02) and oil separation test (ASTM D6184-17). Then, the four-ball test (ASTM D2266-01) was performed to identify the effect of additives on the wear and frictional coefficient behaviour. The blending of MoS2 and BHT improves the physical characterization of grease in terms of dropping point and oil separation. The blending of MoS2 and BHT also helps to decrease the wear diameter and frictional coefficient. Nonetheless, further study is desired to gain a thorough understanding of the processes so that an optimal system can be developed for the industry.

Polyaniline intercalated vanadium pentoxide nanosheets for the improvement of lubricity of base oil

Vanadium pentoxide (V2O5) nanosheets were prepared and tested as an additive to improve the wear/friction-reducing and load-carrying properties of the base lube, paraffin oil. For further advancement of these properties, in situ intercalation of polyaniline (PANI) was achieved hydrothermally using the starting materials as V2O5 powder and aniline. During the process, V2O5 powder was exfoliated into nanosheets, and aniline was oxidatively polymerized under acidic conditions producing polyaniline, which intercalated between the nanosheets to yield the composite PANI-V2O5.nH2O (PVO). Separately synthesized PANI, exfoliated V2O5 nanosheets, and the in situ synthesized composite were characterized by p-XRD, HR-SEM, TEM, FTIR, and XPS. Intercalated PANI prevented restacking of nanosheets and reduced their agglomerating tendencies. A significant increase of interplanar spacing corresponding to the (001) plane of V2O5 in the nanocomposite confirms considerable interaction between the nanosheets and PANI. Although there is no chemical interaction, the non-covalent interactions like hydrogen bonding between the organic and the inorganic components through NH(PANI)...... O-V(V2O5) and van der Waals forces hold the structure firmly. Tribological tests performed on a four-ball tester following ASTM D4172 and ASTM D5183 standards in paraffin oil revealed significant enhancement in friction/wear-reducing and load-carrying properties of the composite compared to V2O5 nanosheets and PANI. The advanced activity of the nanocomposite validates synergy between PANI and V2O5 nanosheets. The morphological studies of the worn surface by SEM and AFM studies endorsed the observed results. The EDX and XPS studies of the tribofilm confirmed the elemental composition and chemical states of all the elements, respectively. A possible mechanism of lubrication has been presented.

Effect of molecular chain length on the tribological properties of two diazomethine functionalised molecules as efficient surface protective lubricant additive: experimental and in silico investigation

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. Highlights 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.

Synergistic effect of molybdenum disulphide and butylated hydroxytoluene in lithium complex grease

Lubricating grease is vital as a sealant and provides extra protection for automotive parts, such as bearings. Bearings are subjected to friction and sliding wear, which results in the degradation of automotive or machinery performance. The present article analysed the effect of molybdenum disulphide (MoS2) and butylated hydroxytoluene (BHT) as grease additives in reducing the frictional and wear behaviour of steel ball bearings. The experiment was conducted by preparing two formulated lithium complex-based grease with a different blending of additives of BHT only (LCG 01/18) and MoS2 + BHT (LCG 01/5). The formulated greases were compared with two industrial greases as the controlled parameters. Next, the physical characterization of formulated and industrial greases was conducted which includes dropping point test (ASTM D2265-00), cone penetration test (ASTM D217-02) and oil separation test (ASTM D6184-17). Then, the four-ball test (ASTM D2266-01) was performed to identify the effect of additives on the wear and frictional coefficient behaviour. The blending of MoS2 and BHT improves the physical characterization of grease in terms of dropping point and oil separation. The blending of MoS2 and BHT also helps to decrease the wear diameter and frictional coefficient. Nonetheless, further study is desired to gain a thorough understanding of the processes so that an optimal system can be developed for the industry.

A study on the effect of the addition of copper nanoparticles on the tribological performance of Polyalphaolefin synthetic oil

Lubrication has become a powerful tool for minimizing friction and wear between mechanical contact surfaces. In order to improve the lubricating properties of base oil, nanoparticles are added. The present study investigates the effect of the addition of Cu Nanoparticles on the tribological behaviour of Polyalphaolefin (PAO4) synthetic oil. Tribo four-ball tester is used to determine the Friction Co-Efficient (COF) for pure PAO4 base oil and also with different concentrations (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, and 1.4 wt%) of Cu nanoparticles. The wear surfaces are examined using a Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDX) and a Tool Makers Microscope. It is observed that Cu nanoparticles, when used as an oil additive, offer excellent anti-friction and anti-wear properties. When 1.0 wt% Cu nanoparticles are added to PAO4 oil, the COF (at the contact point) is lowered by 51.85 percent, and the wear scar diameter is reduced as well when compared to pure PAO4 oil.

Experimental Study on Tribological Properties of Polymer-based Composite Nano-additives Suitable for Armored Vehicle Engine Lubricating Oil

Lubricating oil is known as "the blood to maintain the normal operation of machinery", and additives are an indispensable and important part of lubricating oil. In this paper, the Polymer-based Composite Nano-additive (PCNA) suitable for armored vehicle engine lubricating oil was developed, the physical and chemical properties of lubricating oil containing additives were carried out. The results showed that adding an appropriate amount (3 vol.%) of additives could improve the low-temperature fluidity of lubricating oil and improve the kinematic viscosity of lubricating oil without affecting the viscositytemperature characteristics of lubricating oil. The four-ball testing machine, high temperature end face testing machine and engine bench are used to measure the anti-friction lubrication effect and anti-wear ability improvement effect of the additive on lubricating oil. The experimental results show that the additive can effectively improve the antifriction, lubrication and anti-wear performance of lubricating oil. In addition, the addition of the additive can effectively improve the running state of the engine, and the engine noise is obviously reduced. Finally, the additives developed in this paper are compared with three common brand additives in the market by using the high temperature end face testing machine. The results show that the additive developed in this paper has certain advantages in improving the antifriction and lubrication effect of lubricating oil.

3D texture parameters for wear scars after severe regime

PurposeThis paper aims to present an analysis of several 3 D texture parameters for the entire wear scars obtained in severe regime, on a four-ball tester. The aim of this analysis is to correlate the tribological parameter as wear scar diameter to texture parameters.Design/methodology/approachTested lubricants were rapeseed oil, rapeseed oil additivated with 1% Wt nano TiO2 and rapeseed oil additivated with 1%Wt nano ZnO. The severe regime was applied for 1400 rpm and for loads increasing in steps of 50 N, from 500 to 900 N. Several analyzed roughness parameters (height parameters and functional ones) could be related to the evolution of a wear parameter, the wear scar diameter. Comparing the values for neat rapeseed oil and additivated variants, the texture parameters allow for evaluating if the additives protect or not the worn surfaces.FindingsMeasurements pointed out two groups of roughness parameters: one that has an evolution depending on wear scar diameter (WSD) and load (Sa, St, functional parameters) and one including Ssk that has shown no dependence on load and WSD. Also, the functional parameters Spk and Svk follow in a similar manner the wear parameter, WSD, but Sk is the least dependent on load. For the highest load, amplitude parameters such as Sa and St are following the tendency of WSD. Each lubricant has its particular correlation between wear parameters and texture quality, expressed by the help of a set of roughness parameters.Research limitations/implicationsSuch studies help tribologists to rank lubricants based on a combined analysis with wear parameters and texture parameters.Practical implicationsThe results allow for evaluating new formulated lubricants.Originality/valueThe study on the quality on worn surfaces introduces the original idea of analyzing the entire wear scar surface (approximated by an ellipse with the axes as those experimentally measured) by the help of a set of 3 D roughness parameters.

Unexplored solid lubricity of Titanium nanoparticles in oil to modify the metallic interfaces

The nanoparticles (NPs) of Titanium (Ti) were explored for the first time to enhance the tribo-performance of group III base oil. Its Hexagonal Close Packed (HCP) crystal structure indicates the likelihood to show solid lubricity, although nothing is reported on this. Concentration of NPs in oil was varied from 0.1 to 2 wt% in the presence of a dispersant (1 wt%). The anti-wear-AW, anti-friction -AF, and extreme pressure- EP properties of formulated lubricants were evaluated on a four-ball tester with steel–steel contact in a boundary lubrication regime. The EP performance of base oil was unaffected by the addition of NPs. However, a significant reduction in wear (∼45%) and friction (64%) was exhibited by 0.5 wt% of NPs, the highest in the series. The tribo-films formed at the interface of the ball surface during the AW tests were characterized using scanning electron microscopy (SEM), coupled with energy-dispersive X-ray spectroscopy (EDS) and Raman and XPS Spectroscopy. The excellent AW by Ti nano-oils was due to the tribofilm composed of embedded Tiparticles in the form of FeTiO3. The novelty of the work lies in the maiden attempt to explore the lubricity of Ti NPs in oil and to optimize the concentration for best possible enhancement in AW and AF performance.

A Contact Characteristic of Roller Bearing with Palm Oil-based Grease Lubrication

Grease lubricants are widely used in rolling contact applications to reduce friction between two rolling surfaces. Improper lubrication may cause high contact stress and deformation to the bearings and lead to machine failure The purpose of this study is to investigate the coefficient of friction produced by newly developed palm oil-based grease and to investigate the contact characteristics in lubricated roller bearings. In this work, the coefficient of friction of new greases was evaluated experimentally and the values were compared with the conventional mineral oil-based grease to investigate the friction performance. The friction test was performed using a four-ball tester. The finite element model was developed based on the roller bearing geometry and the simulation was carried out the evaluate the contact characteristic. The experimental result shows that the palm oil grease formulation A had the least coefficient of friction, followed by palm oil grease formulation B, mineral grease and food grade grease. This indicates that palm oil-based grease has the potential to be applied in rolling contact applications due to low friction characteristics. Finite element analysis shows that the maximum von Mises stress and total deformation for frictional contact are higher than the frictionless contact. For the frictional contact analysis with various lubricant COF, similar values were obtained with von Mises stress at 400.69 MPa and 3.4033×10-4 mm deformation. The finding shows that the small difference in grease COF did not affect the rolling contact. The finding also shows that the newly developed biodegradable grease has a similar performance in terms of rolling contact friction and contact characteristic in a condition that the bearing is operating in normal condition.

Influence of oleic acid-treated LaF3 nanoparticles as an additive on extreme pressure properties of various grades of polyalphaolefins

The present work focused on the extreme pressure characteristics of different grades of polyalphaolefins (i.e., PAO 4, PAO 6, PAO 40, and PAO 100) with LaF3 nanoparticles as an additive. The LaF3 nanoparticles were synthesized by the sol-gel method and modified with oleic acid. The synthesized nanoparticles were characterized with various analytical tools viz. X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The varying dose (0.025-0.15 wt.%) of synthesized nanoparticles were blended in all PAOs to prepare nanolubricants. The extreme pressure (EP) properties of nanolubricants were measured using a four-ball tester as per ASTM D2783 to find the last non-seizure load (LNSL), initial seizure load (ISL), just before weld (JBWL), weld load (WL), and load wear index (LWI). The results revealed that the incorporation of LaF3 nanoparticles efficiently enhanced the EP properties of all PAOs. However, 0.15 wt.% of additive was the optimum dose in all PAOs, demonstrating the best EP behavior, i.e., the highest LWI and lowest wear scar diameter (WSD) at ISL and JBWL. Numerous characterization techniques such as scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and scan probe microscope (SPM) were adopted to investigate the probabilistic rationale for the improvement in EP properties.

Antioxidant behavior and tribological performance of a novel multifunctional additive in complex lithium grease

PurposeThis paper aims to contrastively investigate the antioxidant behavior and tribological performance of a novel multifunctional additive (PBT) and dialkyldithiophosphate (ZDDP) in complex lithium grease (CLG).Design/methodology/approachPBT was successfully synthesized through esterification reaction. The antioxidant behavior of PBT and ZDDP was investigated by thermal analysis, and meanwhile, their tribological performance was evaluated by Optimol SRV-IV oscillating reciprocating friction and wear tester (SRV-IV test) and MRS-1J four-ball tester (Four-ball test). Furthermore, their anticorrosion ability was determined by copper strip corrosion test.FindingsFour-ball tests showed that the extreme pressure property of PBT was a little inferior to that of ZDDP. Besides, all the other results demonstrated that PBT showed more superior antioxidation stability, friction-reduction and antiwear ability, as well as anticorrosion performance than ZDDP.Originality/valueThis work provides a study of hindered phenol derivative as a multifunctional additive in lubricant grease, which can contribute to the development of substitution of ZDDP.

Tribological characteristics of mahua oil with graphene nanoplatelets as anti-wear and extreme pressure additive

The tribological investigation was performed to seek the role of graphene nanoplatelets (GNPs) in enhancing the physico-tribological properties of mahua oil. The flashpoint, fire point, viscosity, wear preventive characteristics (WPC) and extreme pressure characteristics (EPC) were conducted following the governing standards. A substantial decrement of 17% in the coefficient of friction, 15.15% in wear scar diameter was observed upon blending the 0.25 wt.% GNPs with mahua oil. The WPC morphology on the steel balls portrayed the micro tracks. The EPC investigation presented 1 wt.% GNPs blended mahua oil with the augmented outcome of 7.7% and this was portrayed to be the best GNPs loading in weld load perspective. However, at 0.1 wt.% of GNPs loading was identified as the best loading with a wear point of view. The morphology of EPC revealed severe abrasion and steel balls were exposed to very high temperatures and have undergone metal squeeze out from the contact surface. This article also discusses the different wear regimes and corresponding wear phenomena in four-ball tribology testing with the aid of micrographs.

Preparation and Tribological Properties of Lanthanum Stearate Modified Lubricating Oil for Wire Rope in a Mine Hoist.

In view of the serious friction and wear on the surface of a hoisting wire rope caused by the failure of lubrication under severe hoisting conditions, a study on the tribological characteristics of lanthanum stearate modified lubricating oil (LSMLO) was carried out. First, lanthanum stearate was prepared by the saponification reaction, and its surface morphology, chemical structure, thermal stability, and dispersion stability in IRIS-550A lubricating oil (IRIS) for wire rope were analyzed. Then, the tribological properties of LSMLO were investigated through four-ball friction tests and sliding wear tests of wire ropes. The results show that stearic acid almost completely reacts to produce lanthanum stearate, which has good thermal stability and a disordered layered structure. With the help of oleic acid, the dispersion stability of lanthanum stearate in IRIS can be significantly improved. The four-ball friction tests show that the optimal addition amount of lanthanum stearate in IRIS is 0.2 wt.%, and the CoF and wear scar diameter are reduced by about 35% and 25% respectively when lubricated with LSMLO compared to that with IRIS. LSMLO can better reduce the wear of the wire rope under different sliding speeds and contact loads than IRIS, and it exhibits improved anti-friction and anti-wear properties under high speed and low load.

Lubricating oil deterioration modeling and remaining useful life prediction based on hidden semi-Markov modeling

Lubricating oil, which carries information about machine’s health condition, is of great importance to the performance of machines in the full life cycle. The main purpose of oil deterioration modeling and its remaining useful life prediction is to determine the exact time that the lubricating oil has degraded and it is no longer able to maintain its functions. Generally, lubricating oil deterioration can be partially detected by condition monitoring based on wear debris analysis, and thus can be categorized into three states. In our paper, vector data, which contain wear debris concentration and carry information about the state of lubricating oil, are obtained by an on-line visual ferrograph sensor from a four-ball tester at regular sampling epochs. The oil’s state process is described by a hidden semi-Markov model, and its sojourn times in each state are assumed to be Erlang distributed. A vector autoregressive method based on time series modeling is presented to obtain residual observations, which are regarded as the observable process of oil information in the hidden semi-Markov model framework. The unknown parameters of the hidden semi-Markov model are then estimated by using expectation-maximization algorithm. Afterward, a Bayesian updating approach is presented to derive the explicit formulas of the conditional reliability and mean residual life. To validate the proposed approach, a real case study of lubricating oil deterioration is demonstrated and a comparison with the hidden Markov model is given to illustrate the effectiveness of the new developed remaining useful life prediction approach for lubricating oil.

Frictional Performance of an Ionic Liquid/Graphene Composite Additive in Lubricating Oil

In this study, we used a four-ball friction and wear testing machine to test the tribological properties of [HPy]BF4 ionic liquids (ILs), low-layer graphene (G), and IL and G compounds (IL/G) as lubricant additives at variousconcentrations, loads, and speeds. The morphology of the wear scar was characterized by a white-light interferometer and a scanning electron microscope (SEM). The results showed that the optimal concentrations of IL and G were 0.10[Formula: see text]wt.% and 0.05[Formula: see text]wt.%, respectively. When the IL concentration was 0.10[Formula: see text]wt.%, the friction coefficient and the wear scar diameter (WSD) reduced by approximately 18% and 8%, respectively, compared to the base oil. When the concentration of G was 0.05[Formula: see text]wt.%, the friction coefficient and WSD reduced by approximately 23% and 12%, respectively, compared to the base oil. After adding the optimal concentration of the IL/G composite additive under the same test conditions, the average friction coefficient of the steel ball reduced by approximately 30%, and the average WSD reduced by approximately 18%. IL/G nanoadditives could be easily attached to the pit area on the friction surface of the steel ball, which made the contact surface of the friction pair smoother and the area of the oil film bearing the load larger, compared to those using the base oil. These two combined phenomena promoted synergistic antifriction and antiwear effects, which significantly improved the frictional performance of the base oil.

Tribological study of TiO2 nanoparticles modified with stearic acid as additives in lithium grease

Purpose The purpose of this paper is to improve the properties of metal nanoparticles which are easy to agglomerate and hard to disperse evenly, thus limiting the application of metal nanoparticles in grease. A novel technology was proposed for modifying metal oxide to improve the dispersibility of nanoparticles. Design/methodology/approach SA-TiO2 nanoparticles were synthesized using an in-situ esterification method followed by surface modification with stearic acid. The microstructure of the nanoparticles was characterized by scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy and their thermal stability was evaluated by thermogravimetric analyzer. The tribological properties of the SA-TiO2 nanoparticles as additives in lithium grease were evaluated with a four-ball tester and TE77 reciprocating friction tester. The worn surfaces of the steel balls were investigated by EDS and XPS. Findings The prepared nanoparticles can be well dispersed in the lithium grease and possess much better tribological properties compared to traditional nanoparticles. The results indicated that the excellent tribological performance of SA-TiO2 was attributed to the chemical reaction film composing of Fe2O3, iron oxide and other organic compounds. Originality/value This paper provides a method to prevent the agglomeration of nano-TiO2 by surface modification with stearic acid. And the prepared nanoparticles can effectively improve the tribology performance of lithium grease.

Carbon Nanoparticles of Varying Shapes as Additives in Mineral Oil Assessment of Comparative Performance Potential.

In this work, carbonaceous nanoparticles (NPs) of varying morphology, viz., multilayer graphene (lamellar, thickness ∼ 3-7 nm), graphite (spherical ∼70 nm), and multi-walled carbon nanotubes (tubular), were selected to explore their tribo-potential in oil under identical operating conditions. A series of nano-oils were prepared using API group III mineral base oil with a dispersant (1%) and selected NPs in incremental concentration (0.5-4%). The tribo-performance of oils was evaluated on a four-ball tester and SRV-IV for extreme-pressure, antiwear (AW), and antifriction performance. Formulations were characterized for density, viscosity, and viscosity index. The stability of oils was monitored through visual observation weekly. Results revealed that the graphene particles showed excellent wear-preventive ability as an AW additive with (41-50) % increase followed by nanographite. Worn surfaces were studied to understand the plausible wear mechanism using a different spectroscopic technique. Tribo-behavior performance was supported with lateral force microscopy on the surfaces of tribo-films.

Synergistic lubrication effect of antioxidant and low content ZDDP on PFPE grease

PurposeThe purpose of this study is to reduce the use of Zinc dialkyl dithiophosphates (ZDDP) and improve the frictional properties and thermal oxidation stability of Perfluoropolyether (PFPE) grease by adding antioxidant additives. The addition of antioxidants can reduce the consumption of ZDDP as an antioxidant, thus improving the anti-wear efficiency of ZDDP and reducing the excess phosphorus element in the grease.Design/methodology/approachIn this study, an antioxidant with good comprehensive performance was selected from several antioxidants by tribological tests and high-temperature tests. Then, the effect of its combination additive with ZDDP on PFPE grease was investigated. The anti-wear property, anti-friction property, thermal oxidation stability and extreme pressure property of greases containing different proportions of ZDDP and antioxidant were tested by four-ball tester and synchronous thermal analyzer (STA). The effects of additives on properties of grease were analyzed by SEM, EDS, LSCM, XPS and FT-IR.FindingsThe research shows that 2,6-Di-tert-butyl-4-methylphenol (BHT) can be used as an antioxidant in combined additives to reduce the antioxidant reactions of ZDDP, thus improving the anti-wear efficiency of ZDDP and further enhancing the anti-wear performance of the grease. Moreover, BHT and ZDDP have a synergistic effect on the high temperature performance of the PFPE grease due to their different antioxidant mechanisms.Social implicationsIn this paper, the problems related to PFPE grease are studied, which has a certain guiding effect on the industrial application of fluorine grease and the related formulation design.Originality/valueIn this paper, the properties of PFPE grease under different lubricating condition were studied. The synergistic lubrication effect of antioxidant and ZDDP are discussed. It provides experimental and theoretical support for reducing the content of ZDDP and improving the performance of additives.

Natural emulsifier assisted lubricity of the colloidal system: Effect of natural emulsifier concentration

Environmental needs, human health issues, government regulations have motivated this work to explore an alternative to mineral oil-based systems to vegetable oil-based environmental friendly lubricants. The present study is an attempt to use natural products (soybean oil and Gum Arabic) to develop environmental friendly oil-in-water emulsion to be used as metalworking fluid. The role and effect of Gum Arabic (GA) concentration on emulsion stability, wettability, and lubricity is explored. Three concentrations of GA corresponding to critical micelle concentration (CMC), below CMC and above CMC are selected to formulate the emulsions (Formulated fluids (FFs)). The emulsion characteristics (droplet size and zeta potential), pH, wetting dynamics, and lubricity are evaluated using dynamic light scattering (DLS), pH glass electrode, Goniometer, and four-ball tester (FBT), respectively. Worn surfaces are analysed using Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscope (FESEM). The physical characteristics and tribological responses suggest that the FF @ CMC of GA exhibited better stability, lubricity, and antiwear properties than other formulations. Different responses of FFs are benchmarked with that of mineral oil-based commercial fluid (CF). FF @ CMC of GA showed a better anti-friction and similar anti-wear response as compared to CF. The excellent lubricity of the FF @ CMC of GA is attributed to the formation of the low shear strength stable lubricious film due to the active participation of GA molecules at the tribo-pair interface.