Antiwear Additives Research Articles

Experimental Investigations to Enhance the Tribological Performance of Engine Oil by Using Nano-Boric Acid and Functionalized Multiwalled Carbon Nanotubes: A Comparative Study to Assess Wear in Bronze Alloy

In various mechanical systems, lubricants are generally used to reduce friction and wear; thus, the total energy loss in the mechanical systems can be minimized by the proper enhancement of lubrication properties. In general, friction modifiers and antiwear additives are used to improve the tribological properties of the lubricant. However, the use of these additives has to be phased out due to their fast chemical degradation in their applications and other environmental issues. In recent years, the use of nanoparticles as a potential lubricant additive has received considerable attention because of its excellent mechanical and tribological characteristics. The present work describes the tribological behavior of nano-boric acid, multiwalled carbon nanotubes (MWCNTs), and functionalized multiwalled carbon nanotubes (FMWCNTs) modified with carboxylic acid. These nanoparticles were used to enhance the tribological properties of engine oil (SAE20W40) used to lubricate bronze alloy samples. The performance of these nano-coolants was assessed on a linear reciprocating ball-on-flat tribometer. Results highlight the friction and wear behavior of the nano-boric acid, MWCNTs, and FMWCNTs under three varying parameters such as the effect of nanoparticles concentration, load-carrying capacity, and sliding speed. The addition of nano-boric acid, MWCNTs, and FMWCNTs has significantly improved the tribological properties of the base lubricant. The addition of 0.5 wt.% of nano-boric acid, MWCNTs, and FMWCNTs to the base lubricant has decreased the coefficient of friction by 19.76, 30.55, and 35.65%, respectively, and a significant reduction in wear volume by 55.17, 71.42, and 88.97% was obtained in comparison with base lubricant.

Effects of extreme pressure and anti-wear additives on surface topography and tool wear during MQCL turning of AISI 1045 steel

The paper presents an original study of the influence of extreme pressure and anti-wear (EP/AW) additives on the surface topography of double-phase steel during turning with different cooling media and variable flow rates. The obtained surface topographies were compared using frequency and fractal analyses for dry, minimum quantity cooling lubrication (MQCL), and MQCL + EP/AW methods. Results showed that the addition of phosphate ester-based additives to an active medium caused the formation of tribofilm on the tool-chip interface and thus a change in the lubricating properties by reducing friction. The tool wear and the formation of the thin-layered tribofilm were also incorporated. The application of the MQCL method with the EP/AW additives led to a decrease in particular surface topography parameters from 8 % to 38 % in comparison with the effects of dry cutting and from 6 % to 35 % in comparison with the effects of machining under MQCL conditions. An exception was the result obtained for the surface roughness height parameter Sp, which was higher than that obtained after the MQCL + EP/AW process for the lowest investigated feed per revolution f = 0.1 mm/rev. This observation was correlated with the uneven formation of the tribofilm on the machined surface. The phosphate ester-based additive used in the MQCL + EP/AW method contributed to achieving tool wear that was less than that obtained by the processes conducted under dry and MQCL conditions.

Effects of Using Alternative Extreme Pressure (EP) and Anti-Wear (AW) Additives with Oxy-Nitrided Samples

Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphate-containing lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces.

Wear and friction performance under lubricated reciprocating tests of steel powder mixtures sintered by Spark Plasma Sintering

Abstract Literature indicates that porosity in sintered materials decreases mechanical properties and fatigue resistance. However, given porosity shape and distribution on a surface, it is possible that these small cavities could improve surface lubrication conditions. This work aims to evaluate the effects of porosity, surface finishing, oil viscosity and heat treatment on wear and friction of two sintered carbon steels during lubricated high contact pressure tests. Samples were characterized prior and after tests by SEM, optical profilometry and hardness measurements. Main results showed that surface hardness and porosity controlled wear behavior of sintered material in high load conditions. Rougher material seemed to activate anti-wear additives contained on the lubricant, promoting less worn volume than polished samples.

Fabrication of novel ionic liquids-doped polyaniline as lubricant additive for anti-corrosion and tribological properties

Abstract Two types of ionic liquids-doped polyaniline (ILs-doped PANI) were synthesized based on an improved interfacial polymerization and evaluated as anti-wear and anti-corrosion additives in poly alpha olefin (PAO) and polyurea grease. Their nanostructures and functionalization were analyzed in detail. The anti-corrosion performance of ILs-doped PANI was assessed via salt spray test, which reveals the excellent anti-corrosion performance. Tribological tests demonstrated that ILs-doped PANI as additives can remarkably reduce friction coefficients and wear volumes in PAO and also in polyurea grease. The scanning electron microscope (SEM) micrographs and X-ray photoelectron spectroscopy (XPS) spectra of the worn surfaces suggested the excellent friction reduction and anti-wear abilities of ILs-doped PANI were strongly dependent on the synergistic lubricating effect during the friction process.

The anti-wear efficiency of boron succinimide on engine cylinder liner and piston ring surfaces

Anti-wear additives are important components of the lubricating oils which protect the sliding surfaces from wear. Researches on developing the non-phosphorus catalysis-friendly anti-wear additive still continue due to government’s regulations. One way to provide non-phosphorus anti-wear additive is boron and sulfur addition to succinimides. In this study, boron succinimide used as an anti-wear additive is compared with ZDDPs in a real engine environment by the engine bench tests. Anti-wear performances were evaluated by microscopic and spectroscopic surface analyses on engine cylinder liner and piston rings after 100-h engine running periods for each anti-wear additive. SEM/EDX and XPS analyses were used to evaluate the tribochemical analyses of tribofilms. SEM and AFM were used to evaluate wear mechanisms on cylinder liner and piston ring surfaces. Results showed that boron succinimide can be an alternative anti-wear additive of ZDDPs from the perspective of anti-wear efficiency.

Challenges in Formulating Vegetable Based Metalworking Lubricants: A Review

The hazardous mineral based lubricating oils are being banned worldwide due to their potential negative environmental impact. The mineral based oil does not meet the requirements of metalworking process without the support of anti-wear, extreme-pressure or extreme temperature additives. Because of additives, they become expensive to cater the needs of special requirements in industries. Besides, being environment friendly, vegetable based lubricants have exclusive properties such as high lubricity, polar nature, high viscosity index and flash point and low evaporation rate. Still they have not yet fully replaced mineral based lubricants due to issues related to their oxidation stability and inappropriate chemical structure. The challenges are to improve certain characteristics of vegetable based lubricants along-with excellent tribological properties. Advanced additive technology and chemical modifications of vegetable oils make them fit for the metalworking applications. In this review article, based on the available literature and recently published data, developments related to vegetable based lubricants and its suitability for metalworking operations are reviewed. Also, challenges in formulating vegetable based oils are put-forth.

The Influence of Metal Surfaces on the Effect of Lubricants

An important aspect of tribology and lubrication is the question of the relationships and the predictability of phenomena of the interaction of lubricants with metal surfaces. In recent years studies on interactions of antiwear additives and sulfur carriers have been presented. Significant differences in the interaction with different metal surfaces (C steel or stainless steel) could be observed. Recent studies have shown that a different, especially mechanical, pretreatment of metal surfaces (C-steel) can lead to very different results.

Oil-soluble ionic liquids as antiwear and extreme pressure additives in poly-\u03b1-olefin for steel/steel contacts

To enhance the lubricating and extreme pressure (EP) performance of base oils, two types of oil-soluble ionic liquids (ILs) with similar anion albeit dissimilar cations were synthesized. The physical properties of the prepared ILs were measured. The anticorrosion properties of ILs were assessed by conducting corrosion tests on steel discs and copper strips, which revealed the remarkable anticorrosion properties of the ILs in comparison with those of the commercial additive zinc dialkyldithiophosphate (ZDDP). The tribological properties of the two ILs as additives for poly-α-olefin-10 (PAO10) with various mass concentrations were investigated. The tribological test results indicate that these ILs as additives are capable of reducing friction and wear of sliding contacts remarkably as well as enhance the EP performance of blank PAO10. Under similar test conditions, these IL additives exhibit higher lubricating and anti-wear (AW) performances than those of ZDDP based additive package in PAO10. Subsequently, X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) were conducted to study the lubricating mechanism of the two ILs. The results indicate that the formation of tribochemical film plays the most crucial role in enhancing the lubricating and AW behavior of the mixture lubricants.

Friction- and Wear-Reducing Properties of Multifunctional Small Molecules

Nitrogen- and oxygen-containing compounds were designed empirically and subsequently synthesized, and their rheology, friction, and wear performance as multifunctional base oils (MFBOs) were evaluated. Two of the compounds displayed good viscosity/rheology profiles without the addition of polymeric viscosity modifiers, displaying high viscosity indexes (VIs) above 200. Furthermore, all three MFBOs had lower coefficients of friction compared to well-established and accepted benchmarks. The most significant advancement is their impressive wear improvement by a factor of 5.5 to 70 compared to either of the benchmarks, which is attributed to the polar nature of the base oil which promotes boundary lubrication with metal surfaces. Moreover, these compounds were easily synthesized in one step from commercial starting materials. This work demonstrates that a careful design could provide the features/performance/functions of base oil, rheology modifiers (or VI improvers), and antiwear and friction-reducing additives, all-in one molecule.

Damage Equivalent Test Methodologies as Design Elements for Journal Bearing Systems

The current paper addresses the field of experimental research of journal bearing systems. In this regard, the challenges are dealt with concerning simultaneous testing with a close correlation to the industrial application and with a high resolution of tribological processes. Concerning this aspect, two damage equivalent laboratory test methodologies for journal slide bearing systems are presented, and their ability to visualize certain performance parameters of bearing systems are emphasized (for instance friction performance, (start stop) wear processes, and seizure events). The results clearly emphasize that the applied methodologies provide accurate findings regarding specific effects of selective parameters/changes on the performance of bearing systems, such as polymer overlays may result in improved mixed friction sliding conditions if designed properly, and they provide superior start stop wear resistance; the use of specific corrosion inhibitors can successfully prevent tribo-corrosion on bronze bearings; a decrease of oil viscosity increases solid friction share but decreases fluid friction; lubricant anti-wear additives are able to improve seizure resistance and sliding properties of bearing systems depending on formulation harmonization; and novel bearing material coatings, e.g., sputtered SnCu, can significantly improve emergency running capabilities.

MoS2/WS2 Quantum Dots as High‐Performance Lubricant Additive in Polyalkylene Glycol for Steel/Steel Contact at Elevated Temperature

AbstractHerein, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) quantum dots (QDs) are prepared by a facile and green technique, and characterized by microscopy and spectroscopy. The resulting products display exceptional stability in polyalkylene glycol (PAG) base oil, and are used for the first time as friction reducing and antiwear additives in PAG for steel/steel contact. Tribological measurements indicate that the stable dispersion consisting of PAG mixed with MoS2/WS2 QDs exhibits significant tribological properties compared with pure PAG and PAG containing MoS2/WS2 QDs nanosheets under different loads at elevated temperatures. The excellent tribological behaviors of MoS2/WS2 QDs are attributed to the formation of a boundary lubrication film, which can be generated not only by the physical entrapment of MoS2/WS2 QDs at the ball‐disk contact surfaces, but also by tribochemical reaction between MoS2/WS2 and the iron atoms/iron oxide species.

Quantitative structure tribo-ability relationship of ultra-high molecular weight polyethylene modified by inorganic compounds

PurposeUltra-high molecular weight polyethylene (UHMWPE) has an excellent performance and application value; however, as a tribological material, its main drawback is its poor performance under dry friction, impacting its ability to work in high-speed dry friction conditions. Modification of UHMWPE can be carried out to overcome these issues. A significant number of inorganic materials have been used to modify UHMWPE and provide it with good tribological performance. However, thus far, there has been no systematic investigation into the methodology of modifying UHMWPE. The authors take a quantitative approach to determine the structure tribo-ability relationship and basic principles of screening of inorganic compounds suited to modify UHMWPE.Design/methodology/approachThe tribological properties of modified UHMWPE using a series of inorganic additives have been qualitatively studied by the authors’ research group previously. In this study, basic quantitative structure tribo-ability relationships (QSTRs) of inorganic additives for modifying UHMWPE were studied to predict tribological properties. A set of 15 inorganic compounds and their tribological data were used to study the predictive capability of QSTR towards inorganic additives properties.FindingsThe results show that the anti-wear and friction-reducing properties of these inorganic compounds correlate with the calculated parameters of entropy and dipole moment. Increased entropy and smaller dipole moment can effectively improve the anti-wear and friction-reducing ability of inorganic compounds as UHMWPE additives. Additives with larger molecular weight, lower hardness and lower melting and boiling points provide good tribological properties for UHMWPE. For inorganic compounds to act as UHMWPE additives, the chemical bond should be less covalent and have more ionic character.Research limitations/implicationsOnly 15 inorganic compounds and their tribological data were used to study the predictive capability of QSTR towards inorganic additives properties. If the samples number is more than 30, the other QSTR methodology can be used to study the modified UHMWPE, and the models finding can be more precise.Practical implicationsA QSTR model for modified UHMWPE has been studied systematically. While the results are not more precise and detailed, the model provides a new way to explore the modified UHMWPE characteristics and to reveal new insight into the friction and wear process.Social implicationsBecause the method of studying tribological materials is entirely different from others, the authors want to present the works and discuss it with colleagues.Originality/valueThe paper presents a new method to study the modified UHMWPE. A QSTR is used to study the tribology capability of compounds from calculated structure descriptors. This study uses the Hartree–Fock ab initio method to establish a QSTR prediction model to estimate the ability of 15 inorganic compounds to act as anti-wear and friction-reducing additives for UHMWPE.

Tribological properties of hydrogen free DLC in self-mated contacts against ZDDP-added oil

PurposeThe purpose of this study is to investigate the tribological properties of tetrahedral diamond-like carbon (DLC) films in self-mated contacts in the presence of additivated and non-additivated vegetable oils. DLC films have high practical value due to low friction and low wear properties. On the other hand, vegetable oils are considered to be lubricants for future due to its resource renewability and biodegradability. Sometimes different chemical agents are added to vegetable oils to further improve its tribological properties. Thus, the tribological study of DLC films against additivated oils becomes important.Design/methodology/approachThe tribology tests were conducted in a four ball tribo-meter under the boundary lubricated conditions.FindingsTa-C DLC exhibited 80 per cent lower wear rate under Zinc dialkyldithiophosphates (ZDDP)-added oil compared to that of base oil. In contrast, the friction coefficient under additivated oil was slightly higher than the base oil lubricated case. Moreover, the carbonyl band area as well as the viscosity change of ZDDP-added oil was much smaller than that of base oil. Therefore, ZDDP reduced the wear of DLC film and prevented the oxidation of base oil during tribotests.Originality/valueThis is the first work on the tribological properties of ta-C DLC lubricated with corn oil with and without anti-wear additives.

Development and Use of Antiwear Additions to Lubricating Oil in Order to Increase Wear Resistance of Internal Combustion Engine Moving Contacts

Questions are considered for improving the reliability and wear resistance of cylinder-piston groups by adding antiwear additives to lubricating oil composition. Tribological studies are conducted for a new additive based on molybdenum diselenide that surpasses basic lubricating oil and also some other antiwear additives with respect to reducing wear of CPG materials.

Tribo-Investigations on Oils With Dispersants and Hexagonal Boron Nitride Particles

A dispersant is almost an unavoidable additive in engine oils since it helps to keep the carbonaceous particles in a suspended form. Dispersants can be multifunctional and can therefore interfere with the functions of other additives either synergistically or antagonistically. The present work investigated the influence of four dispersants (with and without particles of hexagonal boron nitride (hBN) on selected lubrication-related properties of the oils using four ball tester. Particles of hBN, though known as effective anti-wear (AW) and anti-friction (AF) additives, did not prove effective in oil in the presence of dispersants. On the other hand, it proved to be a good extreme pressure (EP) additive by showing 27% improvement in weld load (WL). Worn surfaces were examined using scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDAX), and Raman spectroscopy.

Integrated Computation and Experimental Investigation on the Adsorption Mechanisms of Anti-Wear and Anti-Corrosion Additives on Copper

We integrated first-principles calculations and surface characterization techniques to reveal a new molecular adsorption mechanism of antiwear (dialkyl dithiophosphate ester, EAK) and anticorrosion (2,5-bis(ethyldisulfanyl)-1,3,4-thiadiazole, DTA) additives on the Cu surface during the rolling process. For direct comparison of modeling and experiments, the Cu(110) surface was used in the model based on the strong (220) preferred orientation observed in the microstructures of the rolled copper foil. Density functional theory (DFT) calculations were performed to obtain the adsorption energy, the optimized adsorption structures, and the charge transfer due to adsorption for EAK and DTA on the Cu(110) surface. It was found that the anticorrosion additive, DTA, decomposed and chemically adsorbed on the Cu(110) surface strongly via multiple Cu–N and Cu–S bonds, while the antiwear additive, EAK, adsorbed weakly due to one Cu–O bond. The predicted chemical bonds formation with the Cu surface reasonably agreed wit...

Depressant, antiwear, and antioxidant additives to hydrotreated diesel fuels with low and ultralow sulfur content (Review)

Published data on the influence of sulfur and its compounds on the ecological properties and performance characteristics of diesel fuels have been analyzed. The main characteristics of depressant, antiwear, and antioxidant additives to modern hydrotreated diesel fuels with low and ultralow sulfur content have been considered. A special emphasis is made on the additives based on synthetic and natural high-molecularweight compounds, including complex multifunctional broad-spectrum additives for clean diesel fuels, conforming to the European requirements and quality standards.

Tribological properties of beef tallow as lubricating grease

PurposeThe purpose of this paper is to report on the tribological properties of beef tallow grease and improvements therein through modification with special processing, polymeric compounds and additives.Design/methodology/approachPure original beef tallow grease was used as a biological lubricating grease reference material for the tribological research. Beef tallow was modified and synthesized by adding special biological anti-oxidant additives, LZ anti-wear additives, waste polyethylene terephthalate (PET) polymer compounds and thermally processed graphite.FindingsRheometric measurements indicate that the beef tallow grease modification technology used in this study enables control of the synthesis process to produce lubricants with the required microstructure. Investigation results of the tribological properties of differently modified greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The grease compound with thermally processed graphite has good tribological properties at 300 N load levels. The critical load level of lubricating greases could be significantly increased through the use of anti-wear additives and thermally processed graphite.Originality/valueInvestigation results of the tribological properties of differently modified beef tallow greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The critical load level of lubricating beef tallow greases could be significantly increased using anti-wear additives and thermally processed graphite.

Understanding Tribofilm Formation Mechanisms in Ionic Liquid Lubrication

Ionic liquids (ILs) have recently been developed as a novel class of lubricant anti-wear (AW) additives, but the formation mechanism of their wear protective tribofilms is not yet well understood. Unlike the conventional metal-containing AW additives that self-react to grow a tribofilm, the metal-free ILs require a supplier of metal cations in the tribofilm growth. The two apparent sources of metal cations are the contact surface and the wear debris, and the latter contains important ‘historical’ interface information but often is overlooked. We correlated the morphological and compositional characteristics of tribofilms and wear debris from an IL-lubricated steel–steel contact. A complete multi-step formation mechanism is proposed for the tribofilm of metal-free AW additives, including direct tribochemical reactions between the metallic contact surface with oxygen to form an oxide interlayer, wear debris generation and breakdown, tribofilm growth via mechanical deposition, chemical deposition, and oxygen diffusion.