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The study explored the viability of using waste plastic oil (PO) as an alternative lubricant to petroleum-based lubricants in industrial settings. To enhance the lubrication performance of the PO, this study incorporated cost-efficient, oleic acid-modified, graphene nano platelets [GNP (f)] and hexagonal boron nitride [hBN (f)] nano solid lubricant additives into the PO in various concentrations, forming functionalized nano lubricants. The PO and its functionalized nano lubricant's rheological, dispersion stability, thermal degradation, friction, and wear performance were investigated. Results manifest that incorporating GNP (f) and hBN (f) into the PO significantly enhanced the viscosity and dispersion stability. In addition, it was seen that GNP (f) and hBN (f) nano lubricants lowered the coefficient of friction (COF) by 53% and 63.63% respectively, compared to the PO. However, the GNP (f) and hBN (f) nano lubricants demonstrated a 3.16% decrease and a 50.08% increase in wear volume relative to the PO. Overall, the GNP (f) and hBN (f) nano lubricants displayed a synergistic friction behavior, while they exhibited an antagonistic behavior pertaining to the wear volume. The study elucidated the mechanisms underlying friction and wear performance of the nano lubricants. [ABSTRACT FROM AUTHOR]

Semi‐solid lubricant in the leg joints of insects is represented by tiny cylindrical fragments. The dynamics of lubricant behavior between contact surfaces at the joint scale are investigated using numerical simulation. Results of modeling show that lubricant fragments tend to stick together and form clots of varying shapes and sizes under the influence of shear motion. Formation of such clots, accompanied by constant loss and reproduction of the lubricant, allows maintaining of fluctuating clearance between contact surfaces and helps to reduce friction. Foreign contaminant particles penetrating an open insect joint are removed by the lubricant, to which they stick, reducing abrasive wear. [ABSTRACT FROM AUTHOR]

In recent years Bio-lubricants much desired in numerous applications in machineries due to their renewable characteristics, which have high biodegradable nature and produce fewer pollutants compared to mineral-based lubricants. Thus, in this paper, the effect of bio-lubricant (Cucurbita Pepo L. seed oil) on wear and friction characteristics in pin on disc tester is studied and compared with commercially available lubricant SAE20W40. Tests were conducted at different loads of 10 N, 50 N, 100 N, 150 N and 200 N at a constant speed of 3 m/s for 60 min to evaluate the behaviour of friction coefficient (COF) and wear at a temperature of 28°C and 100°C. It is observed from the results that, the COF decreases whereas, the wear increases with the rise in temperature and load. Cucurbita pepo L. seed oil (CPO) resulted in a lower wear rate in comparison to commercial SAE20W40. Wear scars on the surface lubricated with SAE20W40 show a rougher surface compared to the pin lubricated with CPO at both lower temperature (28°C) and higher temperature (100°C). This shows that CPO has better lubricity than SAE20W40. The present work indicates that CPO can be a possible substitute to mineral-based lubricant SAE20W40 for higher-temperature workplaces. [ABSTRACT FROM AUTHOR]

The appearance, evolution, and proliferation of electric-vehicle motors have introduced new challenges for lubricants. The appearance of electric currents in the shafts of electric motors can dramatically change the original properties of lubricated contacts, leading to mechanism failure. Understanding and controlling this phenomenon can be advantageous for lubrication, but investigating the lubricants requires specific equipment and conditions. Therefore, in this study, we introduced a ball-on-plate reciprocating tribometer capable of applying electric voltage to the elements of the friction pair and measuring the electric contact resistance (ECR) as feedback. Mineral-based paraffin oil was used as a lubricant in this study. The coefficient of friction (COF), wear, surface morphology, and composition were analysed. It was found that high-speed ECR measurement could give valuable information regarding the lubrication conditions in reciprocating friction pairs. This study shows that even tiny currents flowing through the tribo contact can alter the lubricating conditions. Moreover, the polarity of the applied voltage is also of great importance. Applying negative voltage to the harder surface can significantly increase wear if the tribo-film is based on surface oxidation. [ABSTRACT FROM AUTHOR]

While machining of high-strength alloy steel materials, poor surface quality and decreased tool life are result by an increase in the cutting zone temperature close to the machining region. To overcome this, surface texture with green manufacturing environment is an alternate path to enhancing machining performance. In the present work, novel Parallel Grooved Textured Tools (PGT) was developed and studied the performance of so developed tools. Further, the Untextured Tool (UT) and PGT performance was compared while machining EN24 alloy steel under Minimum Quantity Lubrication (MQL) condition. It was perceived from result that textured tools reduced the cutting temperature (CT), rake wear (RW), flank wear (FW), surface roughness (Ra) and cutting force (CF) up to 18.96%, 18.79%, 24.31%, 12.69%, and18.96% respectively compared to UT. [ABSTRACT FROM AUTHOR]

Flood lubrication is often replaced with minimal quantity lubrication (MQL) because of its eco-friendly properties. Surface smoothness, chip removal from cutting regions, improving the tool life, friction reduction at tool/work/chip tip, and temperature reduction during machining are all objectives of the lubricant. Nevertheless, choosing the correct cutting fluid for MQL is seen to be the most pressing issue, even if there are many factors to consider, such as industrial health concerns and environmental contamination. Tool wear, cutting temperature, and surface quality were the focus of this study on machining performance. The experimental settings consist of three machining conditions: oil MQL (OM), ionic liquid (IL) MQL, and LN2. Additionally, there are two various feed rates and three different cutting speeds. Results showed that compared to IL MQL and OM, using LN2 as a cooling medium dramatically reduced cutting temperature, surface roughness, and flank wear. All things considered, the waspaloy is best machined in an LN2 environment. [ABSTRACT FROM AUTHOR]

Bio-lubricants are the future of lubricants as a substitute for mineral lubricants; however, bio-lubricants have drawbacks, such as poor thermal-oxidative stability. In addition, during the friction process, the temperature of the lubricant increases, so the lubricant must have good thermal conductivity to conduct heat to the environment. To combat the drawbacks of bio-lubricants, some additives have been used to improve their performance as lubricants. Composites of carboxymethyl cellulose (CMC)/MXene and Span 60 as surfactants were used as additives in CPO with different compositions. The physicochemical properties of the addition of CMC/MXene and Span 60 in CPO have changed, including kinematic viscosity, TAN, thermal conductivity, and fatty acids, which have a positive impact on lubrication performance in terms of reducing oxidation processes and increasing thermal conductivity. From fatty acid composition tests and FTIR analysis, the additives work to suppress the oxidation process. A pin-on-disk test was performed to evaluate the tribological performances of bio-lubricants. The results show that CM 10 SP (0.5% wt of CMC and MXene and 1% wt Span 60) demonstrated a significant decrease in CoF and wear rate by 49% and 74%, respectively, at a load of 50 N and a speed of 1400 rpm compared to CPO without additives. An interface layer of CMC/MXene and Span 60, separating two surfaces, could induce wear on the surface of the disk and pin. [ABSTRACT FROM AUTHOR]

This research shows the antifriction and antiwear synergies between a phosphonium ionic liquid (IL) and f-WS2 and f-SiO2 nanoparticles (NPs) as additives of a base oil with low viscosity (PAO6). Mass concentrations of 0.1 wt% nanoadditives and 1% IL were selected to formulate the nanolubricants. Pure sliding and rolling–sliding friction tests were performed at 120 °C, finding great friction reductions in comparison with the PAO6 base oil, specifically for the double hybrid nanolubricant (PAO6 + 1 wt% IL + 0.1 wt% f-WS2 + 0.1 wt% f-SiO2). Regarding the wear produced, the greatest antiwear behavior was also achieved for the double hybrid nanolubricant (width reduction of 48% and worn area decrease of 84%). Furthermore, by means of Raman microscopy and roughness examination of the worn surfaces, it can be proposed that the lubrication mechanism of doubled hybrid nanolubricants could be supported by the adsorbed tribofilm (IL and f-WS2) as well as the mending effects (f-WS2 and f-SiO2). [ABSTRACT FROM AUTHOR]

In this study, willow catkins/MoS2 nanoparticles (denoted as WCMSs) have been prepared using a hydrothermal method. The WCMSs were modified with oleic acid (OA) to improve dispersion in base oil. The friction and wear properties of WCMSs in liquid paraffin (LP) for steel balls were investigated using a four-ball wear tester. The results have shown that at a high reaction temperature, willow catkins (being used as a template) and urea (being used as a nitrogen resource) can effectively decrease the wear scar diameters (WSDs) and coefficients of friction (COFs). At a concentration of 0.5 wt.%, the WSD and COF of steel balls, when lubricated using LP containing modified WCMS with urea, decreased from 0.65 mm and 0.175 of pure LP to 0.46 mm and 0.09, respectively. The addition of urea and hydroxylated catkins can generate a significant number of loose nano-sheets and even graphene-like sheets. The weak van der Waals forces, decreasing the shear forces that the steel balls must overcome, provide effective lubrication during rotation. On the other hand, the tribo-films containing MoS2, FeS, azide, metal oxides and other compounds play important roles in reducing friction and facilitating anti-wear properties. [ABSTRACT FROM AUTHOR]

The forthcoming revolution in mobility and the use of lubricants to ensure ecological friendliness intensifies the pressure on tribology for predictors in new life cycles, mainly addressing wear. The current paper aims to obtain such predictors by studying how the wear processes that occur in a standard FE8 bearing test rig under thin film lubrication are conducted by the properties of the lubricant rather than simple viscosity parameters. Assuming that the activity of a lubricant with respect to the temperature, surface, and chemicals is a matter of its chemical potential, the results show that the nature of the base oil is a key parameter, apart from the chemical structure of the additives. Moreover, it becomes clear that chemical predictors are changing by altering the conditions they are exposed to. As an important result, the lubricant is effective in the prevention of wear if it has the capacity to uptake and transmit electrical charges due to its polarisability during a wear process. [ABSTRACT FROM AUTHOR]

Purpose: The adverse effects of temperature on the lubricating properties of nano magnetorheological grease are reduced by applying of a magnetic field. Design/methodology/approach: Nano magnetorheological grease was prepared via a thermal water bath with stirring. The lubricating properties of the grease were investigated at different temperatures. Then the lubricity of the prepared nano magnetorheological grease was investigated under the effect of thermomagnetic coupling. Findings: As the temperature rises, the coefficient of friction of grease lubrication gradually increases, surface wear gradually increases and lubrication performance gradually decreases. Compared with grease, magnetorheological grease has a decreased coefficient of friction and enhanced lubrication effect under the action of a magnetic field at different temperatures. Originality/value: A lubrication method using a magnetic field to reduce the effect of temperature is established, thereby providing new ideas for lubrication design under a wide range of temperature conditions. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the tribological properties of two protic ionic liquids (PILs) under different tribological conditions as a sustainable alternative for mineral oil-based neat lubricants. The synthesis of PILs in this study uses a relatively simple and less expensive method. The Fourier transform infrared (FTIR) spectroscopy results help validate the synthesised PILs' formation. Further, their physicochemical and tribological properties were investigated. The PILs as neat lubricants were tested on a ball-on-plate reciprocating tribometer using bearing steel–bearing steel and bearing steel–aluminium alloy friction pairs at 30 °C and 80 °C. The results show that the investigated PILs significantly reduced the coefficient of friction and wear. The dodecylamine-based PILs performed better in friction and wear reduction than the other investigated lubricants. The formation of the adsorption layer on the friction pairs was assumed to be the dominant friction and wear reduction mechanism. [ABSTRACT FROM AUTHOR]

The growing awareness of reduced friction losses and new demands for electrical powertrains demand improved lubricants. Due to their unique properties, such as high thermal and electrical conductivity, graphene and its derivatives have been investigated for tribological applications, especially as lubricant additives. In this work, we investigated three commercially available graphene variants, one comprising a few layers and the other two comprising nanoplates, after functionalization as additives to lithium soap grease. The grease temperature dropping point increased by approximately 6 °C. Additionally, during the reciprocating friction test, friction increased with the test duration for the baseline grease, whereas it decreased for the ones containing graphene-based additives. On the test end, friction was reduced by 8% compared to the baseline grease. On a four-ball tribometer, the wear scar was reduced from 10 to 18% compared to the baseline grease. In general, no significant difference was seen between the three graphene-based variants. The promising results found with graphene nanoplates, a less expensive material than a few graphene layers, creates opportunities for a cost-competitive additive to commercial greases. [ABSTRACT FROM AUTHOR]

The present study reports the tribological performance of a novel hybrid nano-lubricant for bronze/AISI 4340 alloy-steel tribopair. The hybrid nano-additive used in the present study helps to improve the lubricity and can sustain under extreme conditions. Initially, friction and wear properties are recorded by varying concentrations of Al2O3 (0.5, 0.8, 1.0, and 1.5 wt. %) and GNP (0.05, 0.1, 0.2, and 0.5 wt. %). Based on the results, an optimum hybrid concentration (OHC) is prepared by adding 0.8 wt. % of Al2O3 and 0.2 wt. % of GNP which resulted in 83.84% and 79.75% reductions in coefficient of friction (COF) in comparison to optimum Al2O3-based and GNP-based lubricants, respectively. However, the wear volume (WV) for OHC lubricant indicated 98.28% and 75% reduction in comparison to the above-mentioned lubricants, correspondingly. Extreme pressure (EP) tests were carried out and OHC lubricant reported improved weld point for hybrid nano additive-based lubricant. [ABSTRACT FROM AUTHOR]

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Electrical contacts can be found in all industries today. In these applications lubricants are essential because they protect the metal connectors from friction and fretting corrosion, which generate wear and may lead to an isolating oxide layer and finally the destruction of the electrical connection. Measurements on customary lubricants for electrical connectors were conducted with high regard to oxidation stability, wear and friction characteristics. The selected samples also differ in the thickener systems. Besides typically non-conductive lubricants for electrical contacts, there are lubricants with high electrical conductivity required mainly for EDM bearings (electrical discharge machining) to not promote a system failure. Currently, action is taken in the industry to define standards to measure the electrical conductivity of lubricants. [ABSTRACT FROM AUTHOR]

Purpose: The evaluation of the haptics of water taps and wear-related changes during usage usually involves time- and cost-intensive testing. The purpose of this paper is to abstract the tribo-system between technical ceramic disks of water tap mixer cartridges to the model level and study the tribological behavior. Design/methodology/approach: The friction and wear behavior was studied by means of an alumina ball-on-original alumina disk setup at different temperatures as well as under dry conditions and under lubrication by different greases. Thereby, the frictional behavior was measured in situ, and the wear losses were analyzed by means of laser scanning microscopy. Findings: It was shown that friction and wear can behave in a contrasting way, whereby one grease might lead to low friction, that is, an easy-going movability of the water tap, but to increased wear losses. The latter, in turn, is an indicator for the usability and service life, which cannot be explained from friction alone. Thereby, the viscosity of the base oil, the grease consistency and additives were identified as relevant grease formulation parameters to allow for fluid film (re-)formation and removal of wear particles. Originality/value: To the authors' best knowledge, this is the first approach to systematically analyze the friction and wear behavior of technical ceramic disks of water tap mixer cartridges in dependency on the temperature as well as the used lubricating grease. This approach is relevant for developing screening test strategies as well as for the selection of lubricants for water tap applications. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0334/ [ABSTRACT FROM AUTHOR]

The use of high‐strength aluminum components in automotive manufacturing offers the opportunity to reduce vehicle weight significantly and provide new lightweight potentials. In the past, the so‐called hot forming and quench process (HFQ) successfully demonstrates the potential for the production of complex‐shaped components made out of age‐hardenable high‐strength aluminum alloys. Currently, no method permits wear‐free quench forming without the use of lubricants. To fulfill the increasing ecological and economic requirements, it is necessary to identify wear‐reducing techniques to promote this forming technology in the future. This contribution investigates the interaction of lubricant and tool coatings on the tribological performance during quench forming of the high‐strength aluminum alloy AA7075 at elevated temperatures. For this purpose, the tribological behavior is investigated using both, flat strip drawing tests and deep drawing operations. Subsequently, the component quality is compared and discussed. The results demonstrate that tool coatings are effective for the production of high‐strength components in the HFQ process with minimal or even no lubrication and thus provide ecological as well as economic advantages. [ABSTRACT FROM AUTHOR]

Among the amazing properties of graphene, superlubricity is one of the most promising properties. This property can be used in industrial field components to reduce friction without using liquid lubricants, and therefore, improve machines' efficiency and reliability with low environmental impact thanks to the elimination of oil or grease lubricants. In this paper, copper alloy samples for electrical purposes were coated with graphene by four different deposition processes. The investigated synthesis processes are direct grown graphene on bulk Cu, transferred graphene, and self-assembled graphene from graphene flakes. Ball-on-disk tests were performed to evaluate the tribological performance of samples. The aim was to compare the effect on the tribological performance given by different types of coatings, taking also into consideration industrial scalability. Interestingly, not all graphene nano-coatings being compared proved effective in reducing friction and wear in gross sliding conditions. The results show that the cost-effective self-assembled graphene is the longer-lasting nano-coating among those investigated in this work, and can reduce both friction and wear. Tests revealed that graphene coatings can be applied as a solid lubricant, reducing friction up to 78%, and reducing the average wear volume up to 40%. [ABSTRACT FROM AUTHOR]

The aim of this research was to study the tribological behavior and properties of antifriction polyetheretherketone (PEEK) based composites loaded with solid lubricant particles as well as carbon fibers under both dry friction and water lubrication conditions. The investigated tribological properties varied due to a change in the pattern of the formation and adherence of a transfer film (TF) on the steel counterpart surface. Under the water lubrication conditions, a wear rate increased for the composite loaded with both polytetrafluoroethylene (PTFE) and carbon fibers (CF) due to the suppression of the adherence of a transfer film on the steel counterpart by protruding carbon fibers above the sliding surface, followed by abrasive damage to both rubbed bodies. Therefore, they were not recommended for use in water lubrication bearings. Another composite, loaded with both PTFE and molybdenum disulfide (MoS2) was suggested for using in such bearings according to the 'ball-on-disk' scheme under mixed dry friction/water lubrication conditions. [ABSTRACT FROM AUTHOR]

The urgent need for drastic reduction in emissions due to global warming demands a radical energy transition in transportation. The role of biofuels is fundamental to bridging the current situation towards a clean and sustainable future. In passenger cars, the use of ethanol fuel reduces gas emissions (CO2 and other harmful gases), but can bring tribological challenges to the engine. This review addresses the current state-of-the-art on the effects of ethanol fuel on friction, lubrication, and wear in car engines, and identifies knowledge gaps and trends in lubricants for ethanol-fuelled engines. This review shows that ethanol affects friction and wear in many ways, for example, by reducing lubricant viscosity, which on the one hand can reduce shear losses under full film lubrication, but on the other can increase asperity contact under mixed lubrication. Therefore, ethanol can either reduce or increase engine friction depending on the driving conditions, engine temperature, amount of diluted ethanol in the lubricant, lubricant type, etc. Ethanol increases corrosion and affects tribocorrosion, with significant effects on engine wear. Moreover, ethanol strongly interacts with the lubricant's additives, affecting friction and wear under boundary lubrication conditions. Regarding the anti-wear additive ZDDP, ethanol leads to thinner tribofilms with modified chemical structure, in particular shorter phosphates and increased amount of iron sulphides and oxides, thereby reducing their anti-wear protection. Tribofilms formed from Mo-DTC friction modifier are affected as well, compromising the formation of low-friction MoS2 tribofilms; however, ethanol is beneficial for the tribological behaviour of organic friction modifiers. Although the oil industry has implemented small changes in oil formulation to ensure the proper operation of ethanol-fuelled engines, there is a lack of research aiming to optimize lubricant formulation to maximize ethanol-fuelled engine performance. The findings of this review should shed light towards improved oil formulation as well as on the selection of materials and surface engineering techniques to mitigate the most pressing problems. [ABSTRACT FROM AUTHOR]

It is appreciated that the engine is the heart of the motor vehicle, and the lubricant is considered the blood that ensures its good operation. The life and reliability of any motor vehicle is dependent on the user's attention to care and timely performance of technical overhauls and engine oil changes. The scientific work presents a concrete research carried out by the authors in order to implement some concepts, in which the technical aspects of the lubricants used in the thermal engines of motor vehicles are presented through an analysis of three types of engine lubricant from three major manufacturers in the field. In this way, those interested can learn about the type, technical characteristics, functions, role, necessity and the importance of motor lubricants for the proper functioning of car thermal engines. Finally, the conclusions in the addressed field are presented. [ABSTRACT FROM AUTHOR]

Polyether ether ketone (PEEK) is a widely used material for friction pairs due to its excellent mechanical strength, good wear resistance, and chemical inertness. However, some modifications are necessary when PEEK is used as a water-lubricated friction pair. In this study, a novel sulfonation method was developed to design a water-lubricated friction pair with ultralow friction, good wear resistance, and high loading capacity. PEEK powders were sulfonated using ClSO3H and sintered to form bulk plastic. The sulfonated PEEK (SPEEK) plastic exhibited good tribological properties. At a low sliding speed, the friction coefficient was smaller than 0.02 when a 3 wt% NaCl solution was used as the lubricant. The order of magnitude of the wear rate was as low as 10−8 mm3/(N·m). The mechanism of friction reduction was mainly hydration lubrication. The negatively charged −SO3− groups on the friction pair can adsorb hydrated Na+ cations by electrostatic interactions. These hydrated Na+ cations have a high load capacity and low shearing resistance. The ultralow wear mechanism observed in this study is possibly due to ultralow friction properties of the friction pairs prepared through the proposed sulfonation and thermoforming procedures. [ABSTRACT FROM AUTHOR]

Featured Application: The investigated additives for water-based lubricating fluids could be used in applications where aqueous lubricants are employed. These could be hydraulic or metalworking applications. Lubrication is the primary solution to reduce friction and wear. However, conventional lubricants cause pollution when not properly disposed of or due to accidental leaks. Therefore, environmentally friendly lubricating fluids are welcome in any application where they can meet the performance requirements. This study suggests using coffee oil produced from spent coffee grounds to improve the lubricity of water-based lubricating fluid. Bis(2-hydroxyethyl)ammonium oleate protic ionic liquid facilitates the dispersion of coffee oil in water. Kinematic viscosity, wettability, corrosion prevention, and lubricity tests were performed to evaluate the tribological properties provided by these additives. It was observed that a higher amount of coffee oil could be dispersed with the introduction of a higher amount of protic ionic liquid. In this study, ten wt.% of coffee oil was successfully dispersed using one wt.% of protic ionic liquid. Introducing additives increased dispersions' viscosity, improved wettability, provided protection against corrosion, and reduced wear and friction. It was proposed that polar molecules of protic ionic liquid were responsible for most of the improvement, while coffee oil contributed by increasing viscosity. Further studies could be directed toward determining rational concentration to meet each particular application's requirements. [ABSTRACT FROM AUTHOR]

To improve the tool lubrication performance and reduce the use of cutting fluid as much as possible, a new type of tool with continuous lubrication on the tool-chip contact interface has been fabricated. The atomized cutting fluid can be directly delivered to the tool-chip contact interface through the inner microchannel. Experiments were conducted on the new lubrication method, dry cutting, and traditional MQL cutting of 45 steel. The three-dimensional cutting forces and the cutting temperatures were measured. The wear surface of the rake face was analyzed through SEM micromorphology and EDS element detection. The results showed that the main cutting force of the tool with continuous lubrication at the tool-chip interface decreased by 14.5% and 5.9% compared with the conventional tools of dry cutting and MQL cutting. Moreover, the friction coefficient decreased by 14.2% and 9.8%, the length of the tool-chip contact interface decreased by 35.4% and 19.1%, and the amount of cutting fluid was only 1/10 of that in MQL cutting. The new lubrication method had better cutting fluid penetration and lubrication film formation performance than the traditional MQL method on the tool-chip interface. Furthermore, the surface wear of the new lubrication method was significantly reduced, and the main wear form of the new lubrication method was adhesive wear. [ABSTRACT FROM AUTHOR]

In this second part of the paper series, parameter investigations of the tribological system chain pin/bush contact, carried out on a specifically developed pin on bush plate model test technique, are presented. Both the pin material and the lubricant varied widely. In case of the pin materials, a Cr-N monolayer coating and a Cr-N-Fe-based multilayer coating were investigated. As for the lubricants used, two different performing engine oils from the field were tested as well as fresh oils, some of which were diluted with a soot surrogate (carbon black) and diesel fuel in different amounts. The results show, among other things, that friction and wear performance strongly depend on the combination of pin material and lubricant used. In this context, especially the Cr-N-Fe in combination with the used engine oils showed a high wear resistance and low friction losses compared to the Cr-N reference. In the case of fresh oils with soot, the friction losses were higher but comparable between the pin materials, and a slightly better wear performance of the Cr-N was observed due to an agglomeration effect of the soot surrogate. In general, it was found that especially soot-free oils show clear wear advantages independent of the pin material used. Thus, soot clearly has a wear-promoting component. The investigations of this study suggest that a leading mechanism that is based on a corrosive–abrasive effect in the tested system, but this is more related to the soot surrogate carbon black than engine soot. [ABSTRACT FROM AUTHOR]

In recent years, there has been a challenge: how to meet the requirements of cutting lubrication and use the least cutting fluid for environmental protection simultaneously. To resolve this problem, novel cutting tools with micro textures on the rake face for lubrication were proposed, which can directly transport the cutting fluid to the tool-chip contact interface by using a micro-pipe. Cutting tests were performed on AISI 1045 steel. Then, the cutting force, friction coefficient, tool-chip contact length as well as wear of tools were investigated. The results show that the novel tools with micro textures have better cutting performance than other tools, by using much less cutting fluid than traditional flood lubricating cutting. Especially for the TVT tool, it has the best comprehensive performance. The main lubricating mechanism is that the cutting fluids can be more widely distributed on the tool rake face by the micro textures. This leads to better lubrication and less adhesion of the rake face. [ABSTRACT FROM AUTHOR]

A MoNx coating serves as an effective wear protection layer and is crucial for the investigation of its tribological characteristics at various temperatures. This study examined the tribological characteristics of MoNx coatings that were deposited through high-power pulsed magnetron sputtering (HiPIMS) in an Ar/N2 environment with varying N2 partial pressures. The microstructures and mechanical properties of the coatings were elucidated using scanning electron microscopy, grazing-incidence-angle X-ray diffraction, energy-dispersive spectroscopy, and nanoindentation. The dry friction performances of the coatings at different heating temperatures were studied using a ball-on-disk tribometer. The MoNx coating produced by HiPIMS was composed primarily of fcc−Mo2N and featured a fine, dense column crystal with a maximum hardness of 28.8 GPa. The MoNx coatings exhibited excellent lubrication and wear reduction properties at room temperature (RT). The dry friction performances of the MoNx coatings at elevated temperatures were expected to depend on the growth of the MoO3 tribolayer. At relatively low temperatures (300 °C and 400 °C), the MoO3 tribolayer grew slowly and was not enough to provide good lubrication, causing increases in the dry friction of the coatings. However, the δ−MoN phase formed in the MoNx coating deposited at a high N2 partial pressure could facilitate the formation of MoO3 and thus decreased the friction coefficient at 400 °C. At the relatively high heating temperature of 500 °C, however, the MoO3 tribolayer grew so rapidly that the oxide layer became thick, resulting in an increase in the wear rate. It is believed that tuning the growth rate of MoO3 via optimizing the composition and structure of the MoNx coatings might be a useful way to improve the dry friction at various elevated temperatures. [ABSTRACT FROM AUTHOR]

Wear is one of the most common failures of hydrodynamic bearings. The main purpose of the present work was to investigate the effects of wear on lubrication performance and acquire efficient vibration signatures for fault diagnosis. In this paper, a finite element model (FEM) for a two-disk rotor supported on worn hydrodynamic bearings is presented in which the oil film force is evaluated by linear and nonlinear models. Numerical and experimental results indicate that the static and dynamic characteristics of the bearing are significantly changed by wear, leading to a drop in system critical speeds due to the deterioration of the constraint status provided by the bearings to the rotor. As the wear depth increases, the onset speed of oil whirl increases, while that of oil whip becomes lower, and large amplitudes of resonance and oil whip are more likely to be excited. More notably, all of the above vibration signatures in the y-direction are more sensitive to wear compared to those in the x-direction, which means that wear faults can be diagnosed by differences in vibration characteristics between the x- and y-directions. This research can provide a theoretical foundation and engineering guidance for the hydrodynamic bearing wear fault diagnosis. [ABSTRACT FROM AUTHOR]

The degradation of the lubricant is not possible as they are non-biodegradable and are toxic to nature. Around the globe, various studies are going on while concentrating on bio-based lubricant which could be environment friendly. In this analysis, friction and wear of the Mahua oil-based lubricant have been carried out at different loads. The mahua oil was treated with trimethylolpropane for improving lubrication characteristics and then blended with synthetic oil in the ratio 4%, 8%, and 12% by volume. The proper mixing of the blends was done with help of ultrasonicator. The loads assigned were 20, 80, and 140 N. The tribological analysis at various loads was assessed using a pin on disc tribometer. The sliding velocity of the disc on every load applied has been 0.4 m/s. The lubricating framework that existed during the experiment constituted boundary lubrication. Improvement in frictional behaviour and anti-wear characteristics was shown by 4% and 8% blends of Mahua oil at all the applied loads. The 12% blend shows maximum friction and wear. The worn surface images were better obtained with 4% and 8% blends. [ABSTRACT FROM AUTHOR]

The knowledge of how lubricants contribute to the operational life of a drive train is unclear until now, despite the fact that plenty of literature is available. A novel concept is presented in order to estimate the wear appearing in bearings addressed to the regime of mixed friction with respect to the composition and the so-called "inner" structure of the lubricant. In doing so, the composition is turned into a set of predictors describing the dipolar and inducible dipolar properties of all components as an activity amongst them and toward the surface. The results show that the activity of the solvated specie apparent, stated as the "inner" structure of the lubricant, is closely related to the surface activity and the expected wear. The technique presented here allows a fast computational procedure such that a given lubricant, once known by its constituents, could be explored with respect to the expected wear. Reducing time-consuming tests is desirable by the fact that new materials are forthcoming as a consequence of regulations and evolving green technology. [ABSTRACT FROM AUTHOR]

In this study, the friction and wear characteristics of graphene coatings were evaluated using lubricants with various ratios of graphene ink to deionized (DI) water. When dry graphene ink and pure DI water were used as lubricants, the graphene coating initially peeled off, and the friction coefficient rapidly increased to a large value. However, when a lubricant with graphene ink added to DI water was used, a lubricating film was formed on the graphene coating and the friction coefficient was reduced significantly. Under dry and pure DI water conditions, severe wear morphologies were formed on the graphene coating surface, whereas in the case of the lubricant with graphene inks added to DI water, insignificant wear morphologies were formed. When the mixing ratio between DI water and graphene ink was 100:10 and 100:5, the friction coefficient and wear rate were the lowest, respectively. As a result of a long-term experiment in which the sliding cycle was performed for up to 100,000 cycles under the same experimental conditions, the lubricant with a 100:10 mixing ratio showed excellent lubrication properties, confirming that the friction coefficient and wear rate were significantly reduced compared to that of the dry or pure DI water lubrication conditions. [ABSTRACT FROM AUTHOR]

The rail grease formulation effect in friction, wear, and grease loss due to centrifugal force was evaluated through pin on disc and free flow tests. Six greases were fully formulated so that the effects of the thickener and the base oil viscosity on grease performance could be isolated, since these greases have the same consistency and additive package but different base oil viscosities (50, 200, and 500 cSt) and thickener types (lithium and calcium). The results showed that: (a) lithium greases present lower friction but higher wear than calcium grease; (b) higher kinematic viscosity produces lower wear but higher friction regardless of the thickener type; (c) the critical speed at which grease is expelled from the disc increases with viscosity for lithium-thickened greases and does not depend on viscosity for calcium greases; and (d) lithium greases with high base oil viscosity suit best the wheel–rail interface lubrication, which was verified with the aid of a grease performance index proposed in the present work. [ABSTRACT FROM AUTHOR]

In this paper, the material-lubricant-systems of water lubrication combined with gears made from different tungsten carbide compositions are investigated regarding their behavior concerning wear as well as further gear failures such as scuffing, pitting and tooth root breakage. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to understand how axial cylinder distortions influence the tribological performance of piston ring. The current model contains the effects of axial distortions and ring conformability under mixed to hydrodynamic regimes of lubrication through computational fluid dynamics predictions. The axial cylinder profiles were modelled using series of sinusoidal waves. The effect of axial distortions on ring wear rate was determined using the Archard's model. The ring friction and minimum lubricant film were predicted for low and high combustion pressures near to top dead centre. The study shows that, when the maximum combustion pressure rises, the different wear identities affect the operation of the ring friction much more limited, while the number of sine waves are more pronounced. Finally, it is proved that, even the increase of oil film thickness, it does not presuppose the reduction of friction when it comes to shaping the surface of the cylinder liner. [ABSTRACT FROM AUTHOR]

• Computational modeling of three-dimensional transient wear of thrust bearings in nuclear main pumps. • Positive and negative effects of the presence of scratches on tilting pad thrust bearings. • Effect of scratch wear on bearing lubrication characteristics during rotor start-up and shutdown. A tilting pad thrust bearing wear model based on computational fluid dynamics has been developed, and the wear model was verified and investigated experimentally based on a self-designed test rig. The results show that the presence of scratches results in an increase in oil film pressure, an elevation of the pad center temperature, and a decrease in the minimum oil film thickness. The number of scratches has a more pronounced effect on the lubrication performance of the pad. The test found that the presence of scratches can contain the abrasive chips, which has some positive significance. During the starting process, the pressure center of each ring gradually shifts towards the center of the pad, demonstrating a radial stretching phenomenon. With a further increase in speed, the overall oil film pressure decreases from the center to the periphery, and the influence of scratches on the oil film pressure distribution gradually decreases. [ABSTRACT FROM AUTHOR]

This study aims at the characterisation of physicochemical properties and tribological behaviour of quaternary phosphonium based ionic liquids (QPILs) P44414Sac and P44414Ace at ambient temperature and elevated temperature. The kinematic viscosity, viscosity index (VI), thermal stability, corrosivity and tribological properties of the ionic liquids (ILs) were systematically investigated. The copper strip corrosion test results revealed that the two green ILs are non‐corrosive because of their halogen‐free characteristic. Tribological data demonstrated that the present ILs exhibited extremely superior friction‐reducing and anti‐wear properties to conventional IL lubricant 1‐Butyl‐3‐methylimidazolium hexafluorophosphate (L‐P104), 1‐n‐Octyl‐3‐methyl imidazolium hexafluorophosphate (L‐P108) and commercially available synthetic oil PAO10. Electrical contact resistance (ECR) and surface analysis of the worn‐out steel disc surfaces revealed that the synergistic effect of a polarity induced physical adsorption layer and a tribo‐chemical reaction film formed a boundary film to protect steel‐steel contact between rubbing surfaces. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials with a layered structure can realize extremely low coefficient of friction (COF) at the nanoscale or microscale. However, the highly ordered sliding interface is difficult to be obtained with conventional layered 2D materials, leading to a significantly higher COF at the macroscale. Hence, a novel strategy using "non-layered" 2D materials for macroscale lubrication is proposed in this study. As a "non-layered" 2D material, nanodiamond (ND) plates with thickness as low as several nanometers were used to fabricate solid lubrication coatings with thickness of approximately 3 μm using drop casting method. The ND plates coating reduced the COF by 54.55% compared to that of the ND particles coating, and by 55.13 and 41.92% compared to graphene and MoS 2 coatings, respectively. A transfer layer was formed on the ball surface and a tribofilm with ND plates highly aligned with the sliding direction was formed in the wear track, where the sliding between the ND plates or ND plates and the friction pairs dominates the lubrication performance. Most importantly, the wrinkles and wrapped edge sites commonly observed on layered 2D materials can be eliminated by the high mechanical performance of ND plates, leading to an ordered sliding interface, thus lowering the macroscale COF. This study provides implications for the development of macroscale lubrication systems with "non-layered" 2D materials for engineering applications. [Display omitted] • Nanodiamond plates exhibit excellent solid lubrication performance at the macroscale. • Tribofilms with nanodiamond plates can be formed during the friction process. • An ordered sliding interface can be achieved due to the high mechanical performance of nanodiamond plates. • "Non-layered" two-dimensional materials are promising candidates for macroscale lubrication systems. [ABSTRACT FROM AUTHOR]

This paper presents the influence of three lubrication environments, namely hobbing with minimum quantity lubrication (HWMQL), hobbing with flood lubrication (HWFL), and hobbing without any lubrication (HWAL), on the wear characteristics, microhardness, functional performance parameters, generation of noise and vibrations, flank surface roughness, and microgeometry deviation parameters of spur gears. Convective heat transfer coefficients in HWMQL and HWFL are evaluated to study the cooling mechanism involved and their heat dissipation capabilities during spur gear manufacturing. It is found that HWMQL-manufactured spur gears exhibited higher microhardness and smaller values of microgeometry deviations, flank surface roughness, functional performance parameters, wear rate, wear volume, and noise and vibrations than the spur gears manufactured by HWFL and HWAL. HWMQL facilitated a significantly higher convective heat transfer coefficient than HWFL, indicating its superior hobbing performance. An examination of the worn flank surfaces of HWMQL-manufactured gears revealed a wear track that resulted in less abrasive wear, wear debris, and subsurface damage, whereas the worn flank surfaces of HWFL-manufactured gears showed deep grooves, feed marks, and surface defects. This study proves that HWMQL is capable of manufacturing gears with better accuracy, enhanced wear resistance, smoother and quieter operational performance, and longer service life due to its better cooling and lubrication action. The results of this study will be very helpful for the manufacturers and users of spur gears. [ABSTRACT FROM AUTHOR]

Premature failure caused by inadequate lubrication of an artificial joint is a major problem. Inspired by engine lubrication, in which various additives are used to enforce the oil lubricant, here, a bench test of a biomimetic lubricating fluid containing different substances was carried out. Bovine serum albumin (BSA), in the form of both molecules and nanoparticles, was used as a functional additive. Compared with BSA molecules, BSA nanoparticles dispersed in HA solution served as more effective additives in the biomimetic lubrication fluid to minimize the friction and wear of ceramic orthopedic materials made of zirconium dioxide (ZrO2). Meanwhile, a tribo-acoustic study indicated that the "squeaking" problem associated with ZrO2 could be suppressed by the biomimetic fluid. Together with a cytotoxicity assessment, the BSA nanoparticle-incorporated biomimetic fluid was confirmed as a potential reagent for use in the clinic to maintain an even longer service life of artificial joints. [ABSTRACT FROM AUTHOR]

Graphene-family materials have been investigated by researchers as promising additives for various lubrication systems due to their unique physical-chemical properties. It has been proven that graphene-family materials can lead to enhanced lubrication and wear-resistance performance, which have potential to reduce the energy losses and carbon emissions, and the wear of machines for industrial applications. Experimental, theoretical, and simulation studies have been performed to investigate the tribological behaviors of graphene-family materials as additives. The tribological properties of graphene-family materials, including graphene, reduced graphene oxide, functionalized graphene, and the combination of graphene-family materials and other materials as additives, and the fundamental mechanism are systematically reviewed and concluded. The authors also discuss the potential engineering applications of graphene-family materials as lubricating additives, and the unsolved issues and optimistic outlooks in the near future. [ABSTRACT FROM AUTHOR]

This work investigated the tribological performance of (Ta/ZrN)n multilayer coatings against ultrahigh molecular weight polyethylene (UHMWPE) material. Three multilayer coatings with different designs were deposited on Ti-6Al-4 V substrate and subjected to wear testing under lubrication of diluted bovine calf serum. The results revealed an improvement in wear resistance of (Ta/ZrN)n multilayer coatings and low coefficient of friction under an applied load of 1 N. High hardness, excellent biotribological properties, and low residual stresses were obtained in the multilayer coating with the thinnest ZrN as the topmost layer of 100 nm. This work demonstrates that Ta/ZrN multilayers can be promising coatings for prosthesis applications. [ABSTRACT FROM AUTHOR]

Lubricating oil can effectively reduce friction between mechanical parts, thereby reducing energy consumption and improving service life and reliability. Due to the development of science and technology, it is necessary to improve the performance of lubricating oil to fulfill the higher tribological requirements for countering wear and providing lubrication. Nanolubricant additives have the four lubrication mechanisms of micro-bearing, protective film, polishing, and repair effects. A nanolubricant additive can often demonstrate a variety of lubrication mechanisms at the same time. As lubricating additives, metal and metal oxide nanoparticles have outstanding effects which improve the tribological properties of lubricating oil and have been widely studied in the field of tribology. This paper introduces the lubrication mechanism of nanoadditives and the latest research results for metal and metal-oxide nanoparticle lubrication additives. [ABSTRACT FROM AUTHOR]

Solid lubricants are described as solid materials of intentionally introduced or in situ formed on contact surfaces in relative motion for the purpose of lowering friction and wear and providing protection from damage. Solid lubricants and advanced self-lubricating materials are widely used in modern industries, especially in aerospace, aviation, automotive, metallurgy, materials forming, and machining industries, and have attracted great interest in lubrication applications under very severe circumstances such as elevated temperatures, heavy loads, ultrahigh vacuum, extreme radiation, strong oxidation, and chemical reactivity environments. Many efforts have been made to develop self-lubricating composites by a variety of material preparation techniques, which include powder metallurgy, physical/chemical vapor depositions, thermal spraying, electrodeposition, laser cladding, and additive manufacturing. Although several reviews on the development of high-temperature solid lubricants have been published, most of them only focus on a type of material, a specific process, or application. In this paper, a comprehensive review is provided to present the state-of-the-art progress in solid lubricants, self-lubricating composites/coatings, and their effective functions that can be used over a wide variety of environmental conditions, especially at elevated temperatures. The solid lubricants considered include representative soft metals, layered structure materials (e.g., graphite, hexagonal boron nitride, transition metallic dichalcogenides, MAX phase), chemically stable fluorides, binary or ternary metallic oxides, especially alkaline earth chromates, and sulfates, and synergistic effects from these solid lubricants. This paper also provides new insights into design considerations of environmental adaptive solid lubrication, and the challenges and potential breakthroughs are further highlighted for high-temperature solid lubrication applications. [ABSTRACT FROM AUTHOR]

The use of vegetable oils as lubricants in automobiles is rapidly increasing due to the prevailing environmental aspects. Vegetable oils are also suitable for other applications because they come from renewable and sustainable natural sources and have high biodegradability and low toxicity. Nanoparticles have been extensively investigated for a long time as potential performance improvers of traditional antifriction and antiwear additives because of their inherent properties such as size and shape. The primary aim of the study is to investigate the use ofjatropha oil mixed with graphite, molybdenum disulfide (M0S2), and titanium dioxide (TiCh) nanoparticles as a nanoparticle bio lubricant. The nanoparticles of graphite, molybdenum disulfide, and titanium dioxide are added in varying weight percentages to jatropha oil and a tribological analysis is carried out using a pin-on-disc tribometer. The analysis is focused on tribological quantities, such as coefficient of friction, wear volume, and frictional force. The experiment was carried out for 5 minutes under varying loads at different disc speeds. At an optimum concentration of nanoparticles, the coefficient of friction, frictional force, and the wear rate were found to have the lowest values, but when the level of nanoparticles increases above the optimum level, the friction coefficient and wear rate seem to be increased. The pin-on-disc experiments revealed that nanographite powder mixed in jatropha oil gives better tribological performance than the other two tested nanopowders. Subsequently, multiple regression models are developed using input and output variables. A non-linear fit between the response and the corresponding significant parameters is considered. [ABSTRACT FROM AUTHOR]

Water lubrication has been widely used in marine equipment, where rubber bearings and seals suffer intense friction and severe wear under mixed and boundary conditions. It has good research prospects and practical value to study the composite of amorphous carbon on water lubrication rubber to improve lubrication and reduce wear. In this work, modified graphite-like carbon films incorporated with titanium and nitrogen ((Ti:N)-GLC) were integrated on nitrile butadiene rubber (NBR) with multi-target magnetron sputtering. Direct current (DC) sputtering of graphite target was used as the carbon source. The incorporation of Ti and N elements was accomplished by using radio frequency (RF) magnetron sputtering of three different targets: Ti, TiC and TiN, to optimize the mechanical and tribological performance. This work is aimed to clarify the modification mechanism of Ti and N incorporation and obtain the optimum scheme. The influence of RF power on surface topography, chemical composition, mechanical properties and tribological properties was investigated by SEM, XPS, Raman spectra, nanoindentor and tribometer. The consequences revealed that the characteristics of films depend on RF target types and power. For the Ti-C and TiC-C series, when RF power is 100 W and below, with low content of Ti (6 at.%~13 at.%) and N (around 10 at.%), the incorporation of Ti and N optimizes the surface topology, improves the mechanical properties and maintains excellent adhesion to NBR substrate. The tribological and wear behaviors of (Ti:N)-GLC films are better than GLC films under mixed and boundary lubrication. When RF power grows to 200 W, the dopants result in the deterioration of surface and mechanical properties, followed by worse lubrication and wear behaviors. For TiN-C series, the incorporation of TiN takes no advantage over GLC films, even worse in the case of high RF power. Overall, the incorporation of Ti or TiC by magnetron sputtering in Ar/N2 atmosphere is an effective modification method for GLC films on NBR to improve mechanical and tribological behaviors. [ABSTRACT FROM AUTHOR]

For heat-assisted single point incremental sheet forming (SPIF) works of Ti-6Al-4 V sheets, the use of lubricant has shown significant effects on surface quality and geometric accuracy at higher temperatures. Molybdenum disulphide (MoS2) is a common lubricant widely used in SPIF works, however, it usually indicates ineffective performance at high temperatures. This article has studied different lubricants of MoS2 lubricants and proposed a novel mixture of MoS2 to provide better surface quality and improve geometric accuracy. A forming tool with a ball-roller and water channel was designed to enable the MoS2 mixture to pass through the tool tip, allowing easy application of the lubricant on the localised area and reduce the thermal expansion on the ball-roller. Surface roughness analysis has revealed that the water-cooling MoS2 mixture performed well in reducing friction effects and achieved better geometric accuracy. Forming forces measurements, scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX) and micro-hardness tests also indicated that a higher strain hardening behaviour was detected for the water-cooling MoS2 mixture. [ABSTRACT FROM AUTHOR]

This study investigates the use of an ionic liquid obtained from fatty acids (FAIL) as an additive at 2 wt.% in two different base oils: a mineral oil (M1) and a polyol ester (E1). Physicochemical characterization of the base oil–FAIL blends confirmed the miscibility of the FAIL in the base oils. The addition of the FAIL hardly changed the density of the base oils and the viscosity slightly increased at lower temperatures. The tribological performance of the base oils and their blends with the FAIL was determined using three different tests: Stribeck curve determination and tribofilm formation tests, both under sliding/rolling motion, and reciprocating wear tests. The M1 + FAIL blend showed the lowest friction values under the mixed lubrication regime due to its higher viscosity, while the E1 + FAIL showed the lowest friction values under the elastohydrodynamic lubrication regime, which may well have been due to its higher polarity. Only the E1 + FAIL blend outperformed the antiwear behavior of the base oil, probably because it has better chemical affinity (higher polarity) for the metallic surface. SEM images showed that the predominant wear mechanism was adhesive-type with plastic deformation and XPS studies proved that the presence of increasing amounts of organic oxygen on the wear scar caused better antiwear performance when the E1 + FAIL blend was used. [ABSTRACT FROM AUTHOR]

Aqueous nanolubricants containing ZrO2 nanoparticles, graphene oxide (GO) nanosheets, or hybrid nanoparticles of ZrO2 and GO were formulated using a cost-effective ultrasonication de-agglomeration method. The friction and wear characteristics of these water-based nanolubricants were systematically investigated using a block-on-ring testing configuration with a stainless- and alloy steel contact pair. The concentrations and mass ratios of nanoadditives were varied from 0.02 to 0.10 wt.% and 1:5 to 5:1, respectively, to obtain optimal lubrication performance. The application of a 0.06 wt.% 1:1 ZrO2/GO hybrid nanolubricant resulted in a 57% reduction in COF and a 77% decrease in wear volume compared to water. The optimised ZrO2/GO hybrid nanolubricant was found to perform better than pure ZrO2 and GO nanolubricant in terms of tribological performance due to its synergistic lubrication effect, which showed up to 54% and 41% reductions in friction as well as 42% and 20% decreases in wear compared with 0.06 wt.% ZrO2 and 0.06 wt.% GO nanolubricants. The analysis of wear scars revealed that using such a ZrO2/GO hybrid nanolubricant yielded a smooth worn surface, with 87%, 45%, and 33% reductions in Sa compared to water and 0.06 wt.% ZrO2 and 0.06 wt.% GO nanolubricants. The superior tribological performance can be ascribed to the combination of the rolling effect of ZrO2 nanoparticles and the slipping effect of GO nanosheets. [ABSTRACT FROM AUTHOR]