Extreme Pressure Additives Research Articles

Superlubricity of multilayer titanium doped DLC coatings by using low SAPS organic additives in base oil

This study systematically investigates the tribological performance of titanium doped diamond-like carbon monolayer and multilayer coatings with superior mechanical properties. The coatings were lubricated in poly alpha olefin grade 4 (PAO4) base oil, containing three concentrations of two organic, ashless, and sulfur free (low SAPS) antiwear, and extreme pressure additives with different amounts of phosphorus and nitrogen (Duraphos® 178 and Duraphos® OAP). The multilayer Ti-doped DLC coatings exhibited superior tribological performance compared to uncoated steel, undoped DLC, and monolayer Ti-DLC coatings. They exhibited coefficient of friction values which were in the range of 0.013 and 0.006 (superlubricity) for formulations with Duraphos® OAP. Duraphos® 178 significantly lowered the specific wear rates of both the monolayer and multilayer coatings.

Ionic Liquids as Extreme Pressure Additives for Bearing Steel Applications

The protection of steel surfaces from wear under extreme pressure conditions is of major importance in several industries as it provides better performance and longer life of machinery. The motivation for this work was to study the lubrication of steel by ionic liquids (ILs), which have recently emerged as greener alternatives to commercial lubricants and additives. Three ILs based on sulfur-containing anions, used as 2-wt% additives in polyethylene glycol base oil (MW 200; PEG 200), were tested in the lubrication of ASTM 52100 bearing steel contacts in extreme pressure conditions (under mixed lubrication with a Hertzian pressure of 1.12 GPa) using a mini traction machine (MTM). Due to the poor resistance to corrosion of bearing steel, a semi-ester of succinic acid derivative corrosion inhibitor (Lanxess RC 4801) was added to the mixtures at a 1 wt% concentration. The ILs 1-hexyl-methylimidazolium trifluoromethanesulfonate ([C6mim][TfO]) and 1-hexyl-4-picolinium trifluoromethanesulfonate ([C6-4-pic][TfO]) revealed promising results in terms of surface protection of bearing steel. In contrast, 4-picolinium hydrogen sulfate ([4-picH][HSO4]) as 2-wt% additive to PEG 200 + 1% RC 4801 did not show any improvement in wear performance compared to neat PEG 200 + 1% RC 4801. PEG 200 + 2% [C6mim][TfO] + 1%RC 4801 allowed for a decrease in wear up to ~ 76% and PEG 200 + 2% [C6-4-pic][TfO] + 1%RC 4801 up to ~ 46% when compared with neat PEG 200 + 1% RC 4801. Optical microscopy images suggest the formation of an adsorbed layer, which was further supported by chemical analysis via x-ray photoelectron spectroscopy (XPS) data for [C6mim][TfO].Graphical abstract

Triboelectric Performance of Ionic Liquid, Synthetic, and Vegetable Oil-Based Polytetrafluoroethylene (PTFE) Greases

Within electrical contacts, poor electrical conductivity of lubricants can lead to triboelectric charging, causing electrostatic currents and thermal effects, which accelerate lubrication failure. This study aimed to address these challenges by producing and testing three greases with different base oils: ionic liquid ([Oley][Oleic]), synthetic oil (PAO4), and vegetable oil-based synthetic ester (trimethylolpropane oleate). Each grease was prepared with polytetrafluoroethylene powder as the thickener. The greases were tested using a custom-made tribometer, integrated with a grounded electrical current system, with friction tests conducted with up to a 2 A electrical current flow at a constant voltage supply of 4.5 V. Under triboelectric friction testing, [Oley][Oleic] grease outperformed a commercial perfluoropolyether grease by 27.7% in friction and 16.3% in wear. This grease also showed better performance than formulated lithium grease with extreme pressure additives. The study demonstrates that greases with low interfacial resistance can retain their lubrication capacity under triboelectric conditions. These results indicate that [Oley][Oleic] grease, with its ionic liquid base oil, offers a promising solution for applications involving electrical contacts. This study highlights the potential of using advanced base oils and thickeners to enhance the performance and sustainability of lubricants in demanding environments.

Exploring the Impact of Additives on Tribological Characteristics in Lubricating Oils: A Critical Review

In mechanical systems, lubricants play a crucial role in minimizing friction, dissipating heat, and preventing wear. Additives, comprising both organic and inorganic compounds and typically constituting 0.1% to 30% of lubricant volume, are introduced to enhance lubricant performance. This study investigates the influence of various additives on lubricant behaviour and performance, encompassing antifoam agents, corrosion inhibitors, antioxidants, detergents, extreme pressure additives, pour-point depressants, and viscosity index improvers. Friction coefficients were meticulously measured using a pin-on-disk tribometer to assess the Tribological and physical properties of these additives. Surface analysis via SEM provided insights into wear characteristics influenced by the additives. The comprehensive tribological assessment reveals that the incorporation of additives consistently reduces friction and wear across different base oil types. This underscores the critical role of additives in improving lubricant properties, maintaining thermal stability, and forming protective films on surfaces. Our findings advocate for the strategic use of additives to enhance lubricant performance and longevity.

Performance of Austenitic High-Nitrogen Steels under Gross Slip Fretting Corrosion in Bovine Serum.

Modular artificial hip joints are a clinical standard today. However, the release of wear products from the head-taper interface, which includes wear particles in the nm size range, as well as metal ions, have raised concerns. Depending on the loading of such taper joints, a wide variety of different mechanisms have been found by retrieval analyses. From these, this paper concentrates on analyzing the contribution of gross slip fretting corrosion at ultra-mild wear rates using a bovine calf serum solution (BCS) as the lubricant. The parameters were chosen based on biomechanical considerations, producing wear rates of some ng/m wear path. In parallel, the evolution of tribomaterial (third bodies) was analyzed as to its constituents and generation rates. It has already been shown earlier that, by an advantageous combination of wear mechanisms and submechanisms, certain constituents of the tribomaterial remain inside the contact area and act like extreme-pressure lubricant additives. For the known wear and corrosion resistance of austenitic high-nitrogen steels (AHNSs), which outperform CoCrMo alloys even under inflammatory conditions, we hypothesized that such steels will generate ultra-mild wear rates under gross slip fretting. While testing AHNSs against commercially available biomedical-grade materials of CoCrMo and TiAlV alloys, as well as zirconia-toughened alumina (ZTA) and against itself, it was found that AHNSs in combination with a Ti6Al4V alloy generated the smallest wear rate under gross slip fretting corrosion. This paper then discusses the wear behavior on the basis of ex situ analyses of the worn surfaces as to the acting wear mechanisms and submechanisms, as well as to the tribological reaction products.

Tribological behavior of sulfonitrided tribofilm generated from non-corrosive dimercaptobenzothiadiazole-based additives as effective boundary lubrication layer

Lubricant additives are essential to protect mechanical devices. Although sulfur (S)-based dialkylpentasulfide (RC2540) exhibits acceptable extreme pressure (EP) performance, a high amount of S causes severe corrosion and poorer anti-wear (AW) performance. Herein, dimercaptobenzothiadiazole-based additives (DMTDs) consist of four and five S atoms, namely 2-(benzyldisulfanyl)-5-(benzylsulfanyl)-1,3,4-thiadiazole (4SBZ), 2-(octyldisulfanyl)-5-(octylsulfanyl)-1,3,4-thiadiazole (4SC8), 2,5-bis(benzyldisulfanyl)-1,3,4-thiadiazole (5SBZ), and 2,5-bis(octyldisulfanyl)-1,3,4-thiadiazole (5SC8) were synthesized. The synthesized DMTDs are non-corrosive (Grade 1a-1b) compared to RC2540 (Grade 4c). The 10 wt% 5SBZ demonstrated exceptional EP and AW performance than RC2540. The 10 wt% 5SBZ has improved weld load and reduced wear scar area by 5.0 folds and 94.1% compared to naphthenic base oil. The exceptional tribological properties of 5SBZ are attributed to the strong non-covalent interaction between the benzene ring and metal surfaces, high S content, and synergistic effect between S and N. Alternatively, the DMTDs exhibit better AW performance compared to RC2540. The XPS depth profiling demonstrated the formation of sulfonitrided tribofilm after lubrication with synthesized DMTDs. This tribofilm contributed to an excellent boundary lubrication layer for wear protection. The lubrication mechanism was discussed and proposed. This work provides promising DMTDs as EP and AW additives for industrial applications.

Chemical Activity of Nascent Surfaces for Tribochemical Reactions of Lubricant Components.

Boundary lubrication characteristics are strongly dependent on tribochemical reactions at the contact interface. There are multiple factors that contribute to the activity of tribochemical reactions and the complexity of this phenomenon. Here, we focused on nascent surfaces created by friction and aimed to clarify their chemical properties. To achieve this, we first developed a method based on a mass spectrometer that can sensitively detect molecular adsorption and reactions on a nascent surface. We used various organic compounds as adsorbates and friction materials such as steel, aluminum, gold, and ceramics and examined adsorption of the organic compounds on the nascent surfaces. The adsorption properties of the additives differed between steel metal oxide and nascent steel surfaces. For example, polar organic phosphates, which are extreme-pressure additives, were more easily adsorbed on oxide surfaces, whereas nonpolar organic sulfur compounds were more easily adsorbed on nascent steel surfaces. Alcohols and ethers also adsorbed on nascent aluminum surfaces, whereas olefins and benzene did not. Nascent gold surfaces showed high catalytic activity. Saturated hydrocarbons and fluorinated compounds, which are chemically inert, were also adsorbed on nascent ceramic surfaces, showing high activity. Hydrocarbon oils decomposed through the influence of frictional heat on a nascent steel surface to generate hydrogen and methane. We applied reactive molecular dynamics to simulate the adsorption phenomenon on iron surfaces. As a result, the adsorption energy obtained by simulation and the experimentally determined adsorption activity correlated well. Thus, adsorption and reaction behaviors on nascent surfaces inferred by our method were theoretically supported. On the basis of the chemical properties of the nascent surfaces obtained here, it is possible to explain boundary lubrication phenomena.

МОДЕРНИЗИРОВАННАЯ МАШИНА ТРЕНИЯ

The study objective is to increase the information value, accuracy and reliability of the experimental assessment results of extreme pressure and antifriction properties of the tested materials. A brief analysis of the work on the creation of test tribo-technical equipment is given. The difference between the designs of friction machines for testing using Reichert and Timken tests is shown. The design of an upgraded friction machine for determining extreme pressure, antifriction and anti-wear properties of lubricants is presented. In the proposed installation, the radial force on the friction unit ("roller - ring" or "bar – ring") is generated by a mechanism of even loading, and the assessment of extreme pressure lubricants is determined at the moment of gripping the rubbing samples, at which the motor shaft stops. As a result of upgrading the machine, it became possible to measure the friction force, the normal load and to read the friction factor, both for the lubricants under study and for friction pairs consisting of structural and instrumental materials. The results of comparative tests on the upgraded friction machine for lubricating and cooling liquids with different contents of extreme pressure, antifriction and anti-wear additives are presented. 
 A new friction machine design based on Reichert machine is developed, which allows testing structural and lubricating materials for friction and wear using both Reichert and Timken tests. At the same time, the accuracy of determining tribo-engineering characteristics of the tested materials is increased. It is found that as a result of equipping the friction machine with an even loading system and force measuring sensors, it becomes possible to determine extreme pressure and anti-friction properties of lubricants and structural materials, as well as to estimate the value of the friction factor.

Investigation of Vegetable Oils and Their Derivatives for the Synthesis of Extreme Pressure Additives.

The harmful effects of wear can be reduced through proper lubrication of the frictional parts. When exposed to excessive loads, the lubricant film is displaced from the surfaces, and even the adhesive lubricant layer may rupture. Additives known as Extreme Pressure (EP) are frequently incorporated into lubricants to minimise wear and avert seizures under high temperature and pressure. Mechanistically, these additives generate a film on the surface through chemisorption. These additives are extensively applied in various lubricants, with the largest quantities being employed in metalworking fluids and lubricating greases. Sulfurized vegetable oils and their derivates can be used as EP additives for lubricants. To conduct the investigations, sulfurized additives were synthesized using different vegetable-based oils and fatty acid esters, and alpha-olefins. In this study, the Four-ball test results were compared to gain a more accurate comprehension of how various raw-material-based additives influence wear and friction. The goal was to select raw materials that could be used with favorable results for the production of EP additives. The objective was to achieve a minimum Four-ball weld load parameter of 2000 N. The experiments revealed that the functional impacts of the synthesized samples are dependent on the type of raw materials employed. Based on the experimental data and the stated criteria, the examined raw materials were found to be suitable for the synthesis of EP additives.

Friction Performance of Self-Emulsifying Esters and Organic Phosphate Esters Mixed Aqueous Solution on the Surface of TB6 Titanium Alloy

Water-based lubrication, due to the poor film-forming ability of water, faces challenges in achieving effective lubrication for titanium alloys. This study systematically investigates the frictional performance of phosphorus-based extreme pressure (EP) additives and self-emulsifying esters (SEE) on the surface of titanium alloy (TB6) under different pressures and temperatures. The core lubricant consists of SEE with nonylphenol polyoxyethylene ether phosphate ester (NPEP), polyoxyethylene oleyl ether phosphate ester (POEP), and alcohol ether phosphate ester (AEP). Results show that SEE significantly improves the film-forming ability of the aqueous solution, while phosphate ester forms a strong chemical adsorption film on the alloy surface via P-O-Ti covalent bonds, enhancing the strength of the lubricating film. The combination of SEE and phosphate esters in the water-based solution enables effective lubrication for titanium alloys. Particularly, the mixture of POEP and SEE demonstrates excellent synergistic effects, making it an ideal blend for water-based cutting fluids for titanium alloys. This study elucidates the lubrication mechanisms and action ranges between different additives, providing important guidance for the development and promotion of water-based cutting fluids.

Tuning the interfacial behavior of extreme pressure lubrication by stearic acid-modified TiO2 nanoparticles

The development of high-performance lubricants under extreme pressure (EP) is of great significance for reducing energy waste and protecting ecology in heavy industries such as aerospace, large machinery, and so on. Sulfurized isobutylene (SIB) has been explored as one of the most effective EP additives for oil-based lubricants and delivered promising friction-reducing performance. However, the excessive corrosion caused by SIB on the metal surface seriously reduces the instrument’s lifetime and hinders its extensive practical application. Herein, we develop stearic acid-modified TiO2 nanoparticles (SA-TiO2) as a lubricant additive to improve the EP lubrication performance of obtained composite lubricant (CL). During EP friction, the SA-TiO2 can tune the interfacial structure of tribopair and form a high-strength nano-ceramic film to improve tribological performance. Meanwhile, the SA-TiO2 can also compensate for the high wear caused by SIB, thus significantly enhancing the antiwear, friction reduction, and EP properties by 27%, 20%, and 25%, respectively, when compared with the traditional lubricant (TL) obtained by only SIB. Benefiting from the above synergistic effects, the CL can significantly lower the SIB contents while maintaining high EP performance (4900 N weld load). These findings demonstrate a promising eco-friendly lubricant and provide new insights into the mechanism study for EP lubrication.

Conventional and Recent Advances of Vegetable Oils as Metalworking Fluids (MWFs): A Review

Vegetable oils have been used as metalworking fluids (MWFs) for many years, particularly in small-scale metalworking operations and in industries where environmental regulations are strict. Before the development of modern MWFs, vegetable oils were one of the most common lubricants used for metalworking tools. The use of vegetable oils can be traced back to ancient civilizations such as Egypt, Greece, and Rome, where olive oil was commonly used to lubricate metal tools and weapons. Today, vegetable oils are used as MWFs in a variety of applications. They are often combined with additives or nanoparticles to enhance their performance, such as improving the lubricity, cooling properties, and stability of the oil, as well as reducing friction and wear on the cutting tool. Additives, such as antioxidants, anti-wear agents, and extreme pressure (EP) additives, can be used to improve the performance of vegetable oils as cutting fluids. Compared to standard MWFs, vegetable oils are generally more biodegradable and environmentally friendly, and can be more cost-effective. However, MWFs may offer superior performance in certain areas, such as lubrication and cooling. Ultimately, the choice of MWFs will depend on the specific requirements of the metalworking operation and the balance between performance, cost, and environmental considerations. As the demand for sustainability and environmental responsibility continues, the use of vegetable oils as MWFs is likely to become even more popular in the future. Overall, vegetable oils offer a viable and potentially attractive alternative to standard MWFs in certain applications. This review highlights both conventional and most recent advances in vegetal oils frequently used as lubricant fluids in manufacturing processes.

Experimental investigation of galling occurrence in sliding contact under high pressure of a manganese phosphate versus steel interface: Comparison of two greases

In OCTG (Oil Country Tubular Goods) field, surface treatments and greases are used to make connections reliable by avoiding galling in metal-metal contacts. This study compares the anti-galling performances and wear behavior of two tribo-systems: steel versus manganese phosphate coated steel contact tested with two different greases. The damage scenario and the kinetics of the involved tribological phenomena will be investigated thanks to a test based on the ASTM G196 standard and appropriate surface analyses. A rotational oscillatory movement is applied on two cylindrical samples under static normal loads. Friction coefficient is computed using torque-sensor records. Counterparts are made of carbon steel of yield strength 550 MPa. One has been subjected to a manganese phosphate treatment to generate a protective layer of few microns thick. The other counterpart is used as machined. Two different industrial greases with anti-wear and extreme pressure additives are tested. Results showed a significant difference of tribological behavior between both greases. XPS analyses are done to understand the composition of the interfacial materials. The protective mechanisms of both greases are compared. Pb-containing grease allows the instantaneous formation of a protective layer whereas Pb-free grease forms a thin and durable protective layer after quite long running-in phase. Manganese phosphate layer participate in the protective layer formation.

Extreme pressure properties of garlic oil: comparative investigations with PAO4 base oil and PAO/garlic oil blend

This study aims at exploring the improvement in extreme pressure (EP) properties with addition of natural Garlic oil as EP additive. Comparative investigations were conducted on PAO4 base oil, Natural Garlic oil (NGO) and PAO4 + 1 wt% NGO (Natural Garlic Oil) for evaluating the extreme pressure properties. The EP tests were conducted on a four ball tester according to ASTM D 2783. The results revealed that NGO possesses significantly good extreme pressure properties having a weld load of 3087N and load wear index of 513N. The results also revealed that NGO could significantly improve the weld load and load wear index of PAO4 base oil. After adding 1 wt% garlic oil to PAO4 the load wear index increased by 62.51% and weld load increased by 25%. This study proposes garlic oil as a replacement to the use of nano-particles as EP additives and aims to eliminate the disadvantages that are prominent with nano-particles without comprising the performance.

The influence of model organosulfur extreme pressure additives and analogues on the corrosion of copper as measured by a wire corrosion test method

AbstractA wire corrosion test (WCT) is used to investigate the influence of model organosulfur extreme pressure additives and analogues. The corrosion response from these compounds is discussed with regards to chemical structural type. Corrosion rates were calculated using the guide in ASTM G31 to provide a measurement in mm/year.

Https://neftemir.ru/doi/№2-2023/synthesis-and-study-of-new-thiocarbonic-and-thiocyanic-acid-derivatives-as-extreme-pressure-additives-to-motor-oils/

The article describes the synthesis of 2-butoxymethoxy-1-bromo-3-chloropropane, new as synthon, on the basis of which a number of new derivatives of 2-butoxymethoxypropylene -2-chloroxanthogenate, diethylditocarbamate and thiocyanates containing a simple ether group in the molecule are obtained. The synthesized compounds were studied as extreme pressure additives in MC-20 oil on a four-ball friction machine (FFM). Research results have shown that these compounds have high extreme pressure properties. The relationship between the extreme pressure efficiency of the obtained compounds with their composition and structure was revealed. It has been established that with the introduction of a simple ether group (-OCH2OC4H9), the tribological properties of these compounds are improved. The structure of 2-butoxymethoxypropylene -2-chloroxanthogenate, diethylditocarbamate and thiocyanates derivatives has been proven by determining their physicochemical characteristics, elemental analysis, and also by IR spectroscopy data.

Синтез противозадирных присадок на основе толуолсульфохлорида и метил-, аллил ксантогенатов

The article is devoted to the current problem, the synthesis of new additives for transmission oils. The authors have synthesized p-toluenesulfomethyl- and allylxanthates, previously undescribed in the literature, obtained by the reaction of p-toluenesulfochloride with methyl- and allylxanthates. Particular attention is paid to the synthesis and structural proof of the synthesized compounds by studying their elemental analysis, physicochemical properties, and IR spectra. The main content of the study is devoted to the study of synthesized compounds as extreme pressure additives for transmisson oils. The authors present comparative tests of the extreme pressure properties of p-toluenesulfomethyl- and allylxanthates, with the known extreme pressure additive LZ-23k, as well as with the aroxycarbonylmethylisopropylxanthate and allyloxymethylisopropylxanthate described in the literature, carried out on a four-ball friction machine (FBM) The analysis of the study data showed a high extreme pressure efficiency of the synthesized compounds. The dependence of the extreme pressure properties of the compounds on their structure is shown. This article may be useful to specialists in the field of synthesis of extreme pressure additives for transmission oils.

Pressure-assisted decomposition of tricresyl phosphate on amorphous FeO using hybrid quantum-classical simulations.

The moving components of combustion engines are operated under harsh conditions of high pressures and temperatures. Extreme-pressure anti-wear additives, such as tricresyl phosphate (TCP), are mixed with base oil to prevent wear through the formation of a lubricant film on the substrate. We studied the effect of liquid pressure on the decomposition pathway of TCP in base oil molecules (2,5-dimethylhexane) using hybrid quantum-classical simulations with density functional theory for electrons. At a temperature of 300 K, we found that: (i) bond-breaking barrier energies of both the OC and PO bonds of TCP decrease monotonically as the liquid pressure increases; (ii) the bond-breaking barrier energy of PO is lower than that of OC at pressures of 0 and 2.0GPa, but is higher at a pressure of 5.0GPa; and (iii) the applied pressure significantly lowers the bond-breaking barrier energies of both OC and PO when the PO bond of TCP is directed upward from the substrate. These findings are explained by the inhomogeneous distribution of base oil molecules around TCP and the steric repulsion of the PO bond of TCP. These results indicate that the internal structures of the lubricant films are pressure-dependent.

Investigation of Raw Materials for Sulfurized Vegetable Oil Based Lubricant Additives

Abstract Extreme Pressure (EP) additives are commonly used in lubricants to reduce wear and prevent seizures at high temperature and pressure. In terms of their mechanism, these build up a film on the surface with chemisorption. This film efficiently prevents metal-metal adhesion. Industrial statistics show that extreme pressure additives are mostly used in metalworking fluids, lubricating greases and engine oils. Sulfurized vegetable oils can be used as EP additives of lubricants. This type of EP additive is ashless, derived from renewable sources and have a lesser negative effect on the environment compared to those that are not derived from vegetable sources. To determine the appropriate vegetable oils to be used as the raw material of EP additives, the structure of triglycerides, cost-effectiveness and availability aspects must be considered. Results of experiments show that rapeseed oil and soybean oil best meet this criteria system.

Wear behavior of environment friendly trimethylolpropane trioleate-based lubricant

PurposeFormulation of mineral-based specialty lubricants without anti-wear (AW) and extreme-pressure (EP) additives is a challenging task. This study aims to propose an environment friendly alternative to mineral-based lubricants with superior wear preventive characteristics.Design/methodology/approachIn this study, analysis of wear under trimethylolpropane trioleate (TMPTO)-based lube using operating parameters of four-ball tester was done. The effects of type of lube oil, temperature, load and speed on specific wear rate were investigated using Taguchi L27 orthogonal array. Based on the Taguchi experimental results and single-to-noise ratios, ranking of the four ball parameters was done. The surface analysis of worn steel balls was carried out using optical microscopic images of wear scar and energy dispersive spectrometry (EDS).FindingsResults depict that the blend of sulfurized additives with TMPTO base oil showed a synergistic effect in terms of reduction in specific wear rate by the formation of protective film layer on the surface. The possible physical or chemical interactions between base oil and additives were studied based on the surface morphology of test balls.Practical implicationsThe formulated lubricant has the potential to be used as a tapping/broaching oil.Originality/valueTo the best of the authors’ knowledge, the paper is a novel study investigating the effect of different additive in TMPTO. The results could prove beneficial in making TMPTO-based lube oil a viable replacement of mineral-based oils.