Zinc Dialkyldithiophosphate Additives Research Articles

Effects of Spectrum Loading and break in period using molybdenum disulphide (MoS2) and zinc dialkyl dithiophosphate (ZDDP) as EP additives in lithium based grease

PurposeThe purpose of variable loading conditions (392 N-785N-392N-785N) with break-in period were used to study interactions between zinc dialkyl dithiophosphate (ZDDP) 0.1 P% (phosphorus) and fine-grade molybdenum disulfide (MoS2) 3%, in different mixtures of NLGI 2 lithium stearate grease. Four-ball wear tests were used to evaluate the tribological properties of different grease mixtures such as coefficient of friction and wear. ASTM 2266 as reported by earlier studies is useful, but it is not representative of real-life applications where variable loads and speeds and different break-in periods play a role and could change the results and the nature of tribofilms.Design/methodology/approachIn this study, chemical and mechanical properties of tribofilms were examined. Moreover, design of experiment was used to examine the data and shorten experimentation time. Research described here is investigating variable loading conditions for real-life applications by using a break-in period of 2 min at the start to minimize asperities and establish a clean surface. Design expert (DOE) analyzes responses to reveal those variables that are single factor and those that are multifactor whether synergistically or antagonistically.FindingsThe results indicated that spectrum loading with break-in period showed reduction in wear when tested in greases with ZDDP/MoS2 combinations. Ramping up or down the load every 7.5 min for a rotational speed of 1,200 rpm and a total of 36,000 revolutions or 30-min time slowed the wear properties of lithium-based grease under different MoS2 and ZDDP concentrations. Experiments indicated that wear was largely dependent on the loading condition and ZDDP additives during specific break-in period at 1,200 rotational speed. It is believed that MoS2 greases perform better under spectrum loading and under constant loading when mixed with ZDDP phosphorus.Originality/valueThis research indicates that there is a synergistic interaction between ZDDP, MoS2 and variable loading especially when a break-in period is applied. The results indicated that wear was largely dependent on the specific speed used with spectrum loading as presented in the energy dispersive spectroscopy and the Auger electron spectroscopy analysis, and thus a 3% MoS2 grease with ZDDP (phosphorus: 0.1 Wt.%) are needed to improve the wear resistance and improve the friction characteristics.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0016/

Preparation and tribological study of novel amide-based organic friction modifiers

We have synthesized two novel amide-based organic friction modifiers(OFMs), namely NIPAOA and NDEAOA, through the addition reaction of oleamine with N-isopropylacrylamide and N, N-dimethylacrylamide. The two OFMs exhibit good solubility in PAO6 base oil. Their tribological performance has been investigated using a line contact both individually and when compounded with the anti-wear additive zinc dialkyldithiophosphate (ZDDP) at temperatures ranging from 40 ℃ to 130 ℃. The results show that NIPAOA and NDEAOA form dual-site adsorption on the tribo-pair surface through the N and O atoms in the head group amide, resulting in the tribo-film exhibiting excellent friction-reducing performance in PAO6 across the temperatures. When compounded with ZDDP, they both exhibit effective synergistic friction-reducing effects, attributed to the formation of a unique tribo-chemical reaction film on the worn surface that contains almost no Fe and its compounds. The formation of the unique tribo-film is partly due to the continuous adsorption of free OFMs on the surface of the formed ZDDP tribo-film, providing a milder contact environment for the tribo-pair, allowing for the continuous polymerization of medium and long-chain zinc dialkyldithiophosphate (ZDDP) to ultimately form a uniform and flat tribo-chemical reaction film which interspersed with nitrogen-containing compounds. Even after long-term testing, the film maintains good stability and abrasion resistance, effectively synergizing friction-reducing and anti-wear properties.

Recent Advancements in Understanding of Growth and Properties of Antiwear Tribofilms Derived from Zinc Dialkyl Dithiophosphate Additives under Nanoscale Sliding Contacts.

Zinc dialkyl dithiophosphate (ZDDP) is a key antiwear additive in lubricants that forms robust phosphate glass-based tribofilms to mitigate wear on rubbing surfaces. The quest to unravel the enigma of these antiwear film formations on sliding surfaces has persisted as an enduring mystery, despite nearly a century of fervent research. This paper presents a comprehensive review of nanotribological investigations, centering on the tribochemical decomposition of ZDDP antiwear additives. The core of the Review explores investigations conducted through the in situ AFM-based technique, which has been used to unveil the underlying stress-assisted thermal activation (SATA) mechanism behind the formation of antiwear tribofilms on diverse surfaces. A thorough analysis is presented, encompassing governing factors, such as compression, shear, and temperature, that wield influence over the intricate process of tribofilm formation. This is substantiated by a spectrum of structural and chemical characterization-based inferences. Furthermore, atomic-scale computer simulation studies are discussed that provide profound insights into tribochemical reaction mechanisms and elucidate the details of chemical processes at atomic level.

Effects of lubricant components on ash-bridge deposition characteristics in the diesel particulate filter

Diesel particulate filter (DPF), an important after-treatment system, is widely used to trap particulates from diesel engines. After many active regenerations of the DPF, non-volatile ash may form an ash bridge phenomenon in the DPF channel. This paper studies the effects of lubricant components on ash-bridge deposition characteristics in the DPF. Four test lubricants were prepared based on the CK-4 standard lubricant with four different additives (Ca-based, Mg-based, compound, and Zinc dialkyl dithiophosphate (ZDDP) additives), which were separately and proportionately blended into diesel fuel to form four different fuels. A particulate loading and active regeneration cycle of the DPF with those fuels were performed on a burner. The results show that mid-channel ash deposits (MCD) and the ash-bridge phenomenon were observed in the DPF with all four fuels, and the ash-bridge was mainly located in the middle region of the DPF channel. Mg-based or ZDDP additives can improve the ash-channel ratio (A: C) of the MCD. Ca- or Mg-based additives can reduce the distribution density of ash bridges and avoid sintering of DPF. Different shapes of ash bridges will cause different blockage rates in the DPF channel. When the blockage rate of the DPF channel is greater than about 70 %, DPF channels near the ash bridge are destroyed.

Mechanochemistry of phosphate esters confined between sliding iron surfaces

The molecular structure of lubricant additives controls not only their adsorption and dissociation behaviour at the nanoscale, but also their ability to reduce friction and wear at the macroscale. Here, we show using nonequilibrium molecular dynamics simulations with a reactive force field that tri(s-butyl)phosphate dissociates much faster than tri(n-butyl)phosphate when heated and compressed between sliding iron surfaces. For both molecules, dissociative chemisorption proceeds through cleavage of carbon−oxygen bonds. The dissociation rate increases exponentially with temperature and stress. When the rate−temperature−stress data are fitted with the Bell model, both molecules have similar activation energies and activation volumes and the higher reactivity of tri(s-butyl)phosphate is due to a larger pre-exponential factor. These observations are consistent with experiments using the antiwear additive zinc dialkyldithiophosphate. This study represents a crucial step towards the virtual screening of lubricant additives with different substituents to optimise tribological performance.

Robust Interfacial Tribofilms by Borate- and Polymer-Coated ZnO Nanoparticles Leading to Improved Wear Protection under a Boundary Lubrication Regime.

This work reports on the development of borate- and methacrylate-polymer-coated zinc oxide nanoparticles (ZnOBM) via a plasma polymerization technique to replace the harmful conventional antiwear additive zinc dialkyl dithiophosphate (ZDDP) in automotive lubricants. Here, the tribochemistry across the interfaces formed between sliding ferrous surfaces and coated and uncoated ZnO nanoparticles is thoroughly studied from the perspective of elucidating the tribofilm formation, wear, and friction performance of a novel ZnOBM-based nanolubricant. Tribological tests conducted under a boundary lubrication regime revealed that oil formulations containing only ZnOBM nanoadditives and a mixture of ZnOBM with a low amount of ZDDP (350 ppm of P) significantly improve wear performance (up to 95%) compared to the base oil. Electrical contact resistance results acquired in situ during tribological tests demonstrated that lubricants containing ZnOBM nanoparticles at sliding interfaces undergo tribochemical reactions to form stable tribofilms that reduce friction and wear. Atomic force microscopy (AFM), X-ray absorption near-edge spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS) analysis revealed that ZnOBM nanoparticles, by themselves, form patchy interfacial tribofilms containing iron borate, boron oxide, and zinc oxide and lead to superior tribological performance. Interestingly, ZnOBM nanoparticles interact synergistically with ZDDP to form a hierarchical interface of boron-doped tribofilms, with zinc-iron polyphosphates at the surface and iron oxide, zinc and iron sulfides in the bulk. These encouraging results suggest the potential effective use of the ZnOBM nanoparticles to significantly reduce harmful levels of ZDDP (350 ppm) in the engine oil without compromising the antifriction and antiwear performance and to develop eco-friendly high-performance lubricant additives.

Tribological characteristics of quinolone derivatives: Theoretical and experimental approaches

Quinolone derivatives (QLDs) as antiwear additives are highly advantageous due to their environmentally benign properties. In the present work, we have study the performance of three QLDs; 9-fluoro-3-methyl-10-(4-methylpiperazin-1-yl)-7-oxo-3,7-dihydro-2H-[1,4]oxazino[2,3,4] quinoline-6-carboxylic acid(QLD-1), 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4 dihydroquinoline-3-carboxylic acid(QLD-2) and 1-ethyl-6-fluoro-4-oxo-7-(piperazin-1-yl)1,4-dihydroquinoline-3-carboxylic acid(QLD-3) in paraffin oil employing a four ball tester and the results are compared with the commercial additive zinc dialkyldithiophosphate (ZDDP). One of the QLDs evinced the outstanding antiwear and antifriction performance. Further through Scanning electron microscopy (SEM), complemented by atomic force microscopy (AFM), a remarkable smoothening of the worn surfaces in presence of QLD seen. Moreover, Energy-dispersive X-ray (EDX) results provide clear evidence of tribofilm formation on the worn surfaces which reduces the wear and friction at steel-steel interface. Density functional theory (DFT) calculations were found to correlate well with the experimental results. Our findings offer new insights for improving the antiwear and antifriction properties with high load bearing capacity. The investigated additives are sulphated ash, phosphorus and sulphur (SAPS) free and work efficiently at a much lower concentration, 0.25%w/v compared to ZDDP whose SAPS contents are very high and performs poorly below 1% concentration.

Preparation of Well-Dispersed Lubricant Additives with Excellent Antiwear Ability Under High Load

The reduced graphene oxide (RGO) decorated with rare earth organic complex, Eu(Phen)(OA)3, was successfully synthesized by a simple hydrothermal process. The prepared RGO/Eu(Phen)(OA)3 composites (RGECs) served as lubricating oil additives in Polyalphaolefin-8 (PAO8) and their tribological properties were investigated by SRV-IV fretting friction and wear testing machine. Experimental results indicate that the dispersion stability of RGECs in base oil PAO8 has been optimized greatly compared with that of graphene. The friction coefficient has no obvious change; however, the service life of the base oil, that is effective lubrication time is greatly extended, which is better than the commercial additive Zinc Dialkyldithiophosphate (ZDDP). Furthermore, adding appropriate amount (0.08 wt%) of RGECs is able to reduce the wear spot area by about 56%, the wear rate by about 37% compared with ZDDP. Moreover, these excellent results are attributed to the synergistic effects of RGO nanosheets and Eu(Phen)(OA)3 powders.

Avocado oil mixed with an antiwear additive as a potential lubricant – Measurement of antiwear and extreme pressure properties

The paper aims to study the antiwear (AW) and extreme pressure (EP) properties of avocado oil mixed with zinc dialkyl dithiophosphate (ZDDP) in concentrations of 1% to 3% by weight for lubrication purposes. The AW and EP tests are conducted as per ASTM-4172 and ASTM-2783 standards respectively. Further, the rheological behavior of avocado oil mixed with ZDDP is determined for varying shear rates of 50 – 2000 s−1. The maximum improvement in the wear properties for avocado oil is equal to 39.8% at 1 wt.%. The load wear index of pure avocado oil increases from 32.6 to 80.3 at 3 wt.% ZDDP whereas, the weld point increases to 252 kgf at 3 wt.% ZDDP. The improvement in the antiwear and extreme pressure properties are attributed to the protective film formation on the tribopairs as characterized by SEM and EDX analysis. Also, the addition of ZDDP increases the viscosity of the oil at all concentrations and maintains the Newtonian behavior of oil.

Formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a diamond‐like carbon (DLC) coating

AbstractDiamond‐like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical‐chemical interactions between diamond‐like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond‐like carbon coating a‐C : H : Zr (ZrCg) in lubricated tribological contacts were analyzed by means of pin‐on‐disc (PoD) tribometer by varying the distances from s = 200 m–3,000 m under boundary and mixed friction conditions at T = 90 °C and a contact pressure p = 1,300 MPa regarding the application of diamond‐like carbon coatings on gears. The base lubricant poly‐alpha‐olefin (PAO) was formulated using the anti‐wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x‐ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.

Synergism in the Action of a Composition Consisting of Ashless Sulfur-Containing Compounds as an Antiwear Additive to Lubricants

Compositions of ashless thio compounds in mixtures with mineral oil and metal-containing detergents were tested as antiwear additives representing variants of model engine oil compositions. The tribological activity for both fresh and oxidized mixtures, in comparison with the efficiency of the industrial additive zinc dialkyldithiophosphate, was investigated using different tribometers that realize different wear conditions for friction pairs. Synergy is noted in the antiwear action of amine salt compositions of dialkyldithiophosphoric acid and methylene-bis-dibutyldithiocarbamate, which in turn ensures the ecological safety of lubricants—low sulfate ash and phosphorous contents.

In Situ Study of Role of Microstructure on Antiwear Tribofilm Formation on AZ91 Magnesium Alloy under Zinc Dialkyldithiophosphate Containing Lubricant

Herein, role of microstructure on friction and wear properties of as‐cast and aged AZ91 alloy is investigated using atomic force microscopy (AFM) in lubricated conditions. The lubricant contains commercial antiwear additive zinc dialkyldithiophosphate (ZDDP), which reduces wear via sliding‐induced antiwear tribofilm. The tribofilm growth is found to be highly sensitive to the local microstructure of the alloy. For the case of as‐cast AZ91 alloy, the tribofilm readily forms on large Mg17Al12 precipitates, whereas α‐Mg matrix shows wear and absence of any tribofilm growth. Interestingly, for the aged alloy, the tribofilm formation on continuous precipitate (CP) and discontinuous precipitate (DP) regions is not observed. The stable sliding contact offered by large precipitates in the as‐cast microstructure is found to be critical for the tribofilm formation. Moreover, the results show a considerable difference in coefficient of friction (COF) for Mg17Al12 in the as‐cast microstructure as compared with that in the aged alloy.

Evaluation of physicochemical and tribological properties of chaulmoogra (Hydnocarpus wightianus) oil as green lubricant base stock

Due to environmental concerns, natural oils are increasingly being used as an alternative to mineral oil-based products such as lubricants. However, the use of edible oil for industrial application adversely affects their availability for edible purposes. Chaulmoogra oil is a non-edible oil obtained from the seeds of chaulmoogra tree that grows in wastelands. The fatty acid constituents of vegetable oils determine their properties. Presence of long-chain cyclic fatty acids like chaulmoogric acid, hydnocarpic acid and gorlic acid distinguishes chaulmoogra oil from other oils. Research on how cyclic fatty acids influence the properties of vegetable oils and affect their efficacy as base oils for lubricants is scarce in the literature. This paper presents a preliminary evaluation of the physicochemical, viscometric, oxidative and tribological properties of chaulmoogra oil as a lubricant base stock. Gas chromatography–mass spectroscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy methods were used for structure elucidation. The viscometric analysis was conducted by using Brookfield viscometer. The tribological performance was evaluated by a four-ball apparatus as per ASTM D4172-94. Thermal and oxidative stabilities were evaluated by thermogravimetric/differential thermal analysis in nitrogen and oxygen environments. Pour point was assessed by ASTM D97 method and differential scanning calorimetry. Chaulmoogra oil has a viscosity of 9.2 cSt at 100 ℃ and a viscosity index of 166. Though the coefficient of friction was better than a commercial lubricant of similar viscosity range (SAE 20W40), the wear scar diameter was comparatively higher. Addition of antiwear additive zinc dialkyl dithiophosphate showed considerable improvement in the wear performance of chaulmoogra oil. Chaulmoogra oil showed a high pour point value around 15 ℃ which needs to be improved by appropriate pour point depressants. Environmental advantage, coupled with non-edible nature of chaulmoogra oil, makes it an excellent base stock for lubricants.

Tribological characteristics of detonation sprayed alumina coatings

Abstract Thermally sprayed aluminium oxide coatings are extensively used for functional applications where high wear resistance is of high significance. Among the various thermal spray coating methods, D-gun (Detonation gun) coating technology produces alumina coatings of excellent quality. Components made with D-Gun coatings are used in industrial as well as automotive applications. There is an increasing need to identify, analyse and determine the improved performance of such coatings. The present work aims to study the characteristics of the bio-lubricant- Esterified coconut oil and its influence on the wear characteristics of such alumina coatings. The effect of the anti-wear additive, Zinc Dialkyl Dithio Phosphate (ZDDP) on the tribological behaviour of the lubricant and hence on the coated samples, has also been studied. The coefficient of friction and wear were found to be decreasing with the addition of ZDDP. The average coefficient of friction was found to be in the boundary lubrication regime

Unique synergism between zinc dialkyldithiophosphates and Schiff base bridged phenolic diphenylamine antioxidants

The effects of four Schiff base bridged phenolic diphenylamine antioxidants (SSPDs) on the multifunctional properties of a traditional additive zinc dialkyldithiophosphate (ZDDP) were studied. Interestingly, it is observed that the cooperation between SSPDs and ZDDP improves the antioxidant, antiwear and extreme pressure of lubricant oil, but does not reduce its anticorrosive property. The EDS and XPS results indicated that a unique interaction was occurred between SSPDs and ZDDP. In addition, the synergistic effect was studied by NMR, which showed that SSPD selectively disintegrated the cage structures (basic form) of the ZDDP to afford a donor-acceptor complex via the coordination of nitrogen of imine to the zinc atom.

Reactivity of oil‐soluble IL with silicon surface at elevated temperature

AbstractThe reactivity of an oil‐miscible ionic liquid, phosphonium phosphate (PP), and the common anti‐wear additive zinc dialkyl dithio phosphate (ZDDP) with a solid surface at elevated temperature in the absence of any tribological motion is investigated. Understanding the thermal film build up, composition, and relative thickness will help in the understanding of lubrication mechanisms once tribological effects are introduced. Attenuated total reflection–Fourier transform infrared (ATR‐FTIR), scanning electron microscopy–energy dispersive spectroscopy (SEM‐EDS), and X‐ray photoelectron spectroscopy (XPS) are employed to characterise silicon surfaces before and after the experiments in terms of surface chemistry and surface morphology. The results show that both additives react with the silicon surface to produce thermal films. However, ZDDP forms a thicker film. PP reacts with the silicon and forms a thermal film, but the reaction rate is self‐limited such that an increase of time to 24 hours does not significantly increase the film thickness.

Analysis of the Chemical and Tribological Properties of Phosphate Glass Layers Developing during Metalworking Processes on Manual Transmission Synchronizers*

Abstract Optimization of machining processes to improve the tribological properties of surface layers has become a subject of industrial development. The modifications caused by manufacturing commonly include changes of topography, hardness or residual stresses. The present study investigates modification of the tribological properties of gear synchronizers by the formation of chemical layers on the metal surface within the final grinding process. These layers similar to phosphate glass emerge from the metalworking fluid additive zinc dialkyldithiophosphate (ZnDTP), which is applied in the process in different concentrations. The layers generated at the surface were measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Tribological experiments were conducted on a special synchronizer test facility. ToF-SIMS depth profiling revealed that higher ZnDTP concentrations in the metalworking fluid led to thicker phosphate glass layers on the machined surface. The layer that was generated by the addition of 5 % ZnDTP to the metalworking fluid led to a more homogenous coefficient of friction and a lower amount of wear in the tribological experiments. However, the addition of further ZnDTP, up to a total amount of 10 %, led to higher fluctuations in the coefficient of friction and increasing wear, likely related to the occurrence of friction oscillations resulting from thicker phosphate glass layers. However, the results indicate a good potential for improving surface layer properties of metal workpieces by adjusting the chemical composition of the metalworking fluid applied in the final machining process.

Tribological Studies of Some Quinoline Derivatives and Their Synergistic Interaction with Phosphate Ester

Antiwear properties of metal and sulfur-free synergistic formulations containing quinoline derivatives (QDs)—4-N-(7-chloroquinolin-4-yl)-1-N,1-N-diethylpentane-1,4-diamine (QD-1), 4-N-(6-methoxyquinolin-8-yl)pentane-1,4-diamine (QD-2) and 1-N,1-N-diethyl-4-N-(6-methoxy quinolin-8-yl)pentane-1,4-diamine (QD-3)—with triphenyl phosphate (PE) in polyethylene glycol (PEG) at a very low concentration, 0.25% w/v of each, have been studied on a four-ball tester using ASTM D4172 and D5183 standards. Phosphorus content in the formulations was significantly reduced compared to the frequently used antiwear additive zinc dialkyldithiophosphate (ZDDP) and it was much lower than the allowed concentration suggested by various norms. The synergistic admixtures, SQD-2 and SQD-3, significantly improved the antiwear properties of base lube compared to the ZDDP/PE/QDs alone but the behavior of SQD-1 is comparable to that of ZDDP. Minimum values of mean wear scar diameter and average coefficient of friction were found to be 0.458 mm and 0.034, respectively, for SQD-3, the admixture with the maximum antiwear efficiency. However, these values were 0.538 mm and 0.083, respectively, for ZDDP, and for base oil the values were 1.185 mm and 0.126, respectively. The load-carrying capacity was found to be much higher for the synergistic formulations than for ZDDP.Atomic force microscopy (AFM) and scanning electron microscopy (SEM) micrographs of the wear track support the tribological behavior of the above additives. The presence of nitrogen, oxygen, and phosphorus in energy-dispersive X-ray (EDX) spectra of the worn surface lubricated with SQDs indicates the adsorption of additive on the surface. The magnificent tribological behavior of SQDs may be attributed to the tribochemical film formed on the steel surface invoking phosphorus–nitrogen synergy. Quantum chemical calculations (density functional theory) for interactions of QDs with a steel surface agree well with the experimental observations.

Effect of Surface Nanocrystallization Pretreatment on the Tribological Properties of Plasma Nitrided AISI 316 L Stainless Steel Under Boundary Lubrication

It has been proved that surface nanocrstallization pretreatment is beneficial to plasma nitriding of steel by enhancing nitrogen diffusion, while the tribological properties of the nitrided nanostructured steel under boundary lubrication are not clear. In this work, AISI 316 L stainless steel with and without ultrasonic cold forging technology (UCFT) pretreatment was plasma nitrided at 500 °C for 4 h. The effects of UCFT pretreatment on the microstructure and properties of the nitrided layer and the tribochemical interactions between the nitrided layer and friction modifier molybdenum dithiocarbamate (MoDTC) and antiwear additive zinc dialkyldithio-phosphate (ZDDP) were investigated using SRV tribometer, scanning electron microscopy (SEM), vickers hardness tester, optical microscope, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Surface analyses confirm the formation of a 20 μm thick nitrided layer on the UCFT-pretreated sample and it had higher hardness than that on the unpretreated sample. Furthermore, the nitrided UCFT-pretreated sample presented better synergetic effect with MoDTC and ZDDP on tribological behaviors than the nitrided unpretreated sample. This is attributed to the higher contents of Mo, S, Zn, P, and MoS2/MoO3 ratio in the tribofilms on the nitrided UCFT-pretreated sample.

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.