Search

A multilayer film, composed by ZrN-Ag (20 nm) and Mo-S-N (10 nm) layers, combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system, to promote lubrication in a wide-range of temperatures. The results showed that the ZrN-Ag/Mo-S-N multilayer film exhibited a sharp interface between the different layers. A face-centered cubic (fcc) dual-phases of ZrN and Ag co-existed in the ZrN-Ag layers, whilst the Mo-S-N layers displayed a mixture of hexagonal close-packed MoS2 (hcp-MoS2) nano-particles and an amorphous phase. The multilayer film exhibited excellent room temperature (RT) triblogical behavior, as compared to the individual monolayer film, due to the combination of a relative high hardness with the low friction properties of both layers. The reorientation of MoS2 parallel to the sliding direction also contributed to the enhanced anti-frictional performance at RT. At 400 °C, the reorientation of MoS2 as well as the formation of MoO3 phase were responsible for the lubrication, whilst the hard t-ZrO2 phase promoted abrasion and, consequently, led to increasing wear rate. At 600 °C, the Ag2MoO4 double-metal oxide was the responsible for the low friction and wear-resistance; furthermore, the observed transformation from t-ZrO2 to m-ZrO2, could also have contributed to the better tribological performance. [ABSTRACT FROM AUTHOR]

Most studies of liquid lubricants were carried out at temperatures below 200 °C. However, the service temperature of lubricants for aerospace and aeroengine has reached above 300 °C. In order to investigate the friction mechanism and provide data for high temperature lubrication, the friction and wear properties of chlorophenyl silicone oil (CPSO)-lubricated M50 steel and Si3N4 friction pairs were investigated herein. Ball-on-disk experimental results show that the lubrication performance of CPSO varies significantly with temperature. Below 150 °C, coefficient of friction (COF) remains at 0.13–0.15 after the short running-in stage (600 s), while the COF in the running-in stage is 0.2–0.3. At 200 °C and above, the running-in time is much longer (1,200 s), and the initial instantaneous maximum COF can reach 0.5. Under this condition, the COF gradually decreases and finally stabilizes at around 0.16–0.17 afterwards. This phenomenon is mainly due to the different thickness of boundary adsorption film. More importantly, the wear rate of M50 steel increases significantly with the temperature, while the wear rate barely changes at temperatures above 200 °C. The anti-wear mechanism is explained as tribochemical reactions are more likely to occur between CPSO and steel surface with the increased temperature, generating the FeCl2 protective film on the metal surface. Accordingly, FeCl2 tribochemical film improves the lubrication and anti-wear capacity of the system. At high temperatures (200–350 °C), FeCl2 film becomes thicker, and the contact region pressure becomes lower due to the larger wear scar size, so the wear rate growth of M50 steel is much smaller compared with that of low temperatures (22–150 °C). The main findings in this study demonstrate that CPSO lubricant has good anti-wear and lubrication capacity, which is capable of working under temperatures up to 350 °C. [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 antiwear properties of tribofilms formed on steel surfaces lubricated with various multi-component lubricants were investigated at an elevated temperature and under load-speed conditions conducive to sliding in the boundary lubrication regime. The lubricants contained base oil, reduced-level (secondary) zinc dialkyl dithiophosphate (ZDDP), and nitrogenous dispersant. The wear resistance of the tribofilms produced from different oil blends was evaluated in the context of the rate of change in the sliding track volume (wear rate for material loss) and the load-bearing capacity, chemical composition, and thickness of the tribofilms. Surface profilometry and scanning electron microscopy were used to quantify the wear performance and detect the prevailing wear mechanisms, whereas X-ray photoelectron spectroscopy elucidated the chemical composition and thickness of the tribofilms. The oil blends without ZDDP did not produce tribofilms with adequate antiwear properties, whereas the oil blends containing ZDDP and dispersant generated tribofilms with antiwear characteristics comparable to those of tribofilms produced from blends with a higher ZDDP content. Although dispersants can suspend oil contaminants and preserve the cleanness of the sliding surfaces, it was found that they can also reduce the antiwear efficacy of ZDDP. This was attributed to an additive-dispersant antagonistic behavior for surface adsorption sites affecting tribofilm chemistry and mechanical properties. Among the blends containing a mixture of ZDDP and dispersant, the best antiwear properties were demonstrated by the tribofilm produced from the blend consisting of base oil, 0.05 wt% ZDDP, and a bis-succinimide dispersant treated with ethylene carbonate. The findings of this investigation demonstrate the potential of multi-component lubricants with reduced-content ZDDP and nitrogen-based dispersant to form effective antiwear tribofilms. [ABSTRACT FROM AUTHOR]

This study introduces a low-friction composite based on PEEK to improve its friction and wear properties. The composite incorporates PTFE as a solid lubricant and utilizes PPTA as a reinforcing material within the PEEK matrix. These components were prepared utilizing a compression molding method, followed by a series of exploratory experiments to identify the optimal preparation conditions for PEEK. This research assesses how the PTFE/PPTA/PEEK composites perform in terms of friction and wear under dry and oil-lubricated conditions. By examining wear tracks using scanning electron microscopy and white light interference microscopy, this study aims to uncover the wear mechanisms of PEEK and its composites under different lubrication scenarios. Results show that the main wear mechanisms for the PTFE/PPTA/PEEK composites and bearing steel are ploughing and adhesive wear. The presence of PPTA helps reduce wear by leveraging its strong fibers and thermal stability, while the coefficient of friction decreases as PTFE creates a smooth, solid lubricating film on the surface. Notably, PEEK composites containing 25 wt% PTFE and 6 wt% PPTA demonstrate the lowest wear rates and reduced coefficient of friction in both dry and oil-lubricated conditions. [ABSTRACT FROM AUTHOR]

Due to the impending depletion of petroleum reserves and environmental worries, the creation of bio-lubricants is a compelling subject of research. With the use of tertiary butylhydroquinone (TBHQ) and Eichhornia crassipes carbon nanotubes (EC-CNTs), this work intends to create an effective sunflower oil-based bio-lubricant and analyze its tribological performance using a ball-on-disk tribo-meter. Different additive concentrations were blended to create the bio-lubricant. The tribological analysis was conducted in terms of coefficient of friction (COF), wear rate, wear scar diameter, surface roughness for different speed, load and temperature. The morphology shows good structures of the employed additives, TGA revealed good thermal resistance, FT-IR indicated good compatibility with needed functional groups. Under tribological test at 1500 rpm, inclusion of additives (SFO + 0.9wt.% EC-CNTs + 0.3wt.% TBHQ) demonstrated good enhancement on sunflower lubrication, thus showing COF and wear rate values of 0.058 and 13.5 10-9 mm3.m-1.N-1 against base sunflower COF and wear rate values of 0.074 and 15.5 *10-9 mm3.m-1.N-1. Under surface roughness, application of additives lowers the roughness on the lubricated surfaces (SFO + 0.9 wt.% EC-CNTs = 0.447 µm), (SFO + 0.3 wt.% TBHQ = 0.453 µm), thus shows smoothest when blended the two additives together (SFO + 0.9 wt.% EC-CNTs + 0.3 wt.% TBHQ = 0.244 µm), against base SFO value of 0.522 µm. The use of additives in SFO shows synergistic result via nano-lubricant tribo-film formation resulting in commended outcome in all the conditions tested. [ABSTRACT FROM AUTHOR]

Poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), as a highly hydrophilic as well as biocompatible material, has been widely used in biomedical applications. In this study, the friction reduction and wear resistance of HXLPE were improved by grafting PMPC on its surface. However, the PMPC will be sheared off during friction, which is difficult to meet the long-term service requirements of artificial joints. This can be achieved by improving the lubrication environment to minimize PMPC shedding. To simulate the human lubrication environment, free PMPC (lubrication factor) and Cu2+ (transition group metal ion catalyst) were added to neonatal bovine serum (NBCS). When the friction pair consisting of grafted PMPC-modified HXLPE and Cu/ZrO2 ceramics is rubbed therein, the grafted PMPC interacts with the free PMPC, while Cu2+ catalyzes the oxidative hydrolysis of serum proteins into carbon-containing small molecules and adsorbs on the surface of the Cu/ZrO2 ceramics to form a carbon-rich lubrication layer. The composite lubrication layer consisting of grafted-free PMPC and carbon-rich lubrication layer provides good load-bearing and lubrication properties at the friction interface. And the wear rate is reduced by 45% compared to rubbing in deionized water. This technique can reduce the shedding of grafted PMPC state and improve the load-bearing performance of the interfacial lubrication layer, thus reducing the wear of HXLPE and prolonging the service life of the artificial joint. [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]

Purpose: This paper aims to investigate the preparation of AlN and Al2O3, as well as the effect of nano-AlN and nano-Al2O3, on friction and wear properties of copper-steel clad plate immersed in the lubricants. Design/methodology/approach: Nano-AlN or nano-Al2O3 (0.1, 0.2, 0.3, 0.4 and 0.5 Wt.%) functional fluids were prepared. Their tribological properties were tested by an MRS-10A four-ball friction tester and a ball-on-plate configuration, and scanning electron microscope observed the worn surface of the plate. Findings: An increase in nano-AlN and Al2O3 content enhances the extreme pressure and anti-wear performance of the lubricant. The best performance is achieved at 0.5 Wt.% of nano-AlN and 0.3 Wt.% of nano-Al2O3 with PB of 834 N and 883 N, a coefficient of friction (COF) of approximately 0.07 and 0.06, respectively. Furthermore, the inclusion of nano-AlN and nano-Al2O3 particles in the lubricant enhances its extreme pressure performance and reduces wear, leading to decreased wear spot depth. The lubricating effect of the nano-Al2O3 lubricant on the surface of the copper-steel composite plate is slightly superior to that of the nano-AlN lubricant, with a COF reaching 0.07. Both lubricants effectively fill and lubricate the holes on the surface of the copper-steel composite plate. Originality/value: AlN and Al2O3 as water-based lubricants have excellent lubrication performance and can reduce the COF. It can provide some reference for the practical application of nano-water-based lubricants. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0255/ [ABSTRACT FROM AUTHOR]

Self-replenishable ways of applying solid lubrication in tribological systems are limited to the use of sintered self-lubricating composites. These are obtained by mixing solid lubricants with metallic powders or by the in situ precipitation of the lubricating phase. Both techniques can produce self-lubricating composites able to promote low friction coefficients in dry sliding conditions. However, the combination of solid lubricant and matrix is limited by the thermodynamic interactions during sintering. Filling the pores of sintered parts with solid lubricants by vacuum impregnation is a versatile way to promote solid lubrication, allowing any combination of solid lubricant and matrix to be used, avoiding deleterious phases and other sintering problems typical in sintered self-lubricating composites. In this work, low alloy sintered steel was produced by mixing Astaloy CRL powders with 0.6 wt% C, the sintered specimens were impregnated with graphite (1.10 μm), and the durability and wear rates of the resulting composites were studied using ball-on-flat reciprocating tests. The results show that the impregnation technique is able to fill the surface pores with graphite, producing friction coefficients down to 0.06 in dry-sliding conditions and wear rates ranging from 10−4 to 10−7 (mm3/N-m). The main wear mechanism of the impregnated specimens was plastic deformation on the surface, which causes sealing of pores, while the wear of the counter-bodies was mainly abrasive. The durability of the lubricity regime is directly proportional to the amount of lubricant available as pores get sealed by the sliding action of the counter-body, so is proportional to the porosity. [ABSTRACT FROM AUTHOR]

CoCrNi medium‐entropy alloy (MEA) is a promising material for aviation and aerospace applications due to its excellent strength and ductility. However, its low surface hardness and poor wear resistance pose challenges for its tribological performance. To address this issue, electrochemical boronizing is explored as a potential solution, offering advantages such as a fast boronizing rate and low cost. This study demonstrates that electrochemical boronizing can significantly enhance the surface hardness and self‐lubrication performance of CoCrNi MEA, as well as retain impressive mechanical performance. Results show that a boronized layer with a thickness of about 50 μm is formed on the surface in 45 min. The boronized layer is mainly composed of Co2B, Ni2B, CrB, CoB, and Ni3B. After boronizing, the surface hardness of the sample increases by about 9 times, and the ultimate tensile strength and uniform elongation can reach 97% and 73% of the original sample, respectively. Compared with the original alloy, the friction coefficient and wear rate of boronized MEA are reduced by 38% and 85% under deionized water conditions, respectively. X‐ray photoelectron spectroscopy analysis reveals the generation of boron‐containing tribofilm on the wear scars, which significantly reduces friction and wear during the friction process. [ABSTRACT FROM AUTHOR]

In our previous work, we find that the ethylene glycol (EG) is transferred to amorphous carbon or graphene during sliding under the effect of the tribochemical reactions; herein, in this work, we control the concentration of the modified Al2O3 nanoparticles in the EG solution in order to modulate the tribological properties of the tribosystem sliding in the mixed lubricant consisting of the modified Al2O3 nanoparticles and EG. The tribological tests show that the concentrations of the modified Al2O3 nanoparticles ranging from 0 to 1.0 wt% in the mixed lubricant are helpful for obtaining low wear rate due to the formation of graphene‐like materials induced by tribochemical reactions. On the other hand, when the concentration reaches 1.5 wt.%, the tribosystem exhibits high coefficient of friction (COF) and wear rate, which is attributed to the formation of reunited groups consisting of the modified Al2O3 nanoparticles and graphene‐like materials. This investigation should give a positive guidance for the design of the mixed lubricant with excellent lubrication properties. [ABSTRACT FROM AUTHOR]

Graphene is considered a good lubricant additive. The lubricating properties of graphene lubricant at different concentrations and temperatures are studied via a four-ball friction and wear-testing machine. The results show that the coefficient of friction (COF) and wear scar diameter (WSD) of the steel ball with 0.035 wt% graphene lubricant decreased by 40.8% and 50.4%, respectively. Finally, through surface analysis, the following lubrication mechanism is proposed: as the added graphene particles can easily fill and cover the pores of the friction surface, the contact pressure of the rough peak is reduced, resulting in a lower COF and smoother surface. Although the COF increases with temperature, graphene lubricants still exhibit good lubrication effects. [ABSTRACT FROM AUTHOR]

A series of polyimide (PI)/V2CTx MXene composites was synthesized via polyamide acids (PAA) and two‐dimensional (2D) V2CTx MXene obtained by etching precursor V2AlC. PI/V2CTx MXene composites with different mass ratios were obtained by blending and heating with PAA. The results showed that V2CTx MXene has excellent dispersion in PI. In particular, V2CTx MXene exhibited excellent friction reduction and anti‐wear properties as a solid lubricant additive, and the wear rate (WR) was reduced by 43.2% by incorporating only 0.8 wt% of V2CTx MXene in the pristine PI and 71.9% by incorporating 1.2 wt%. Scanning electron microscopy (SEM) and x‐ray photoelectron spectroscopy (XPS) analyses showed that the continuous transfer film consisting of a high proportion of tribo‐chemical products formed on the contact surface is significant to improve the lubrication performances of the PI composites. This work broadens the application of MXene in the field of tribology and contributes to energy conservation and sustainable development of human society. Highlights: The tribological properties could be tuned by changing the ratio of PI to V2CTx MXene.The WR of PI composites was reduced by 71.9% with incorporating 1.2 wt% of V2CTx MXene.The formation of transfer films on the contact surface is significant for improving anti‐wear of PI. [ABSTRACT FROM AUTHOR]

Nowadays, one of the most important challenges in the tribology field is to avoid the excessive consumption of soft metals such as Ag at elevated temperatures through the re-design of the self-lubricant films, to achieve the long-term lubricant under the temperature-cycling environments, for widely used in real industrial applications. This paper took up this challenge to develop a novel green film, by composing nano-particles Ag into the amorphous SiN x matrix using magnetron sputtering system, for achieving the long-term lubricant under the room temperature (RT)-500 °C temperature-cycling conditions. Results showed that the film exhibited a dual-phase of face-centered cubic (fcc) Ag and amorphous SiN x. An excellent RT-500 °C wear-resistance performance was observed for the films with the Ag content of 1.3–9.4 at.%, whilst the film at 15.8 at.% Ag exhibited the best anti-frictional performance (COF 0.3–0.5 for RT-500 °C conditions) at the cost of wear rate. The self-lubricant tribology behaviors under the RT-500 °C cycling conditions were mainly attributed by the synergism of: (1) mechanical properties, (2) excellent high-temperature chemical stability of SiN x matrix, and (3) the lubricant nature of Ag and its elevated temperature diffusion behaviors. [ABSTRACT FROM AUTHOR]

In the present work, the functionalisation of austenitic stainless steel, AISI 316L surfaces via nanosecond Nd:YAG laser texturing in order to modify the surface morphology with crosshatch and dimple patterns is presented. A tribological analysis under lubrication with sunflower and jojoba oil with and without the addition of a solid lubricant, MoS2 nanotubes, was performed. In conjunction with friction/wear response laser-textured surface wettability, oil spreadability and oil retention capacity were also analysed. It was shown that the crosshatch pattern generally exhibited lower friction than the dimple pattern, with the addition of MoS2 nanotubes not having any significant effect on the coefficient of friction under the investigated contact conditions. This was found in addition to the better oil spreadability and oil retention capacity results of the crosshatch-textured surface. Furthermore, texturing reduced the wear of the stainless-steel surfaces but led to an approximately one order of magnitude larger wear rate of the steel counter-body, primarily due to the presence of hard bulges around the textured patterns. Overall, the crosshatch pattern showed better oil retention capacity and lower friction in combination with different vegetable oils, thus making it a promising choice for improving tribological performance in various environmentally friendly applications. [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]

Tribological properties are crucial for air-conditioning system performance. The properties can be improved using nanolubricant. However, the effect of the binary ratio of hybrid nanolubricants on the tribological performance of automotive systems is limited in the literature. Therefore, the present study investigates the tribology performance of TiO2-SiO2 nanolubricants for application in automotive air-conditioning (AAC) systems. The dispersion of TiO2 and SiO2 into PVE lubricant was carried out using a two-step method. Subsequently, the dispersion stability was assessed qualitatively and quantitatively. The samples were characterised by a volume concentration of 0.010%, with variations in the mixture ratio of 20:80, 40:60, 50:50, 60:40, and 80:20. Coefficient of friction (COF) and wear scar diameter (WSD) values were determined using the Koehler Four-ball Tribo Tester and Light Compound Microscopy. The investigation revealed that each sample experienced a reduction in COF, with the 40:60 ratio demonstrating the best ratio with the most significant decrease of 37.09%. At the same time, the COF decreased by 8.34%, 2.12%, 7.37%, and 15.11% for the nanolubricant samples at 20:80, 50:50, 60:40, and 80:20, respectively. The WSD evaluation showed that the 40:60 ratio has the lowest scar diameter of 0.0344 mm and a 37.09% wear rate decrease compared to pure lubricant. Each sample exhibits superior performance when evaluated for tribological characteristics and performance, particularly in the case of nanolubricants with the 40:60 ratio. The TiO2-SiO2/PVE, characterised by a volume concentration of 0.010%, has remarkable efficacy across different binary ratios, making it highly recommended with a 40:60 ratio for lubricating AAC compressor systems. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inadequate lubrication of the two touching surfaces during friction can lead to severe wear, especially in metal cutting. Therefore, a surface with synergistic anti-friction effect of texture and solid lubricant was proposed to improve lubrication. A mesh texture with excellent wettability was prepared on the high-speed steel (HSS) surface by laser, and then nylon fibers were vertically implanted into the grooves of the texture using the electrostatic flocking technology. The friction and wear state of different surfaces (smooth, textured, flocking) under dry/oil-lubricated were studied by a linear reciprocating wear tester. The coefficient of friction (COF) under different working conditions was used to analyze the anti-friction properties, and the wear rate was used to evaluate the wear resistance of the surface. The results showed that the tribological properties of flocking surfaces were better than those of the other two surfaces. This is because the addition of nylon fibers eases shear at the edges of the texture. The broken fibers form a solid lubricating film on the specimen surface, which prevents the surface from being scratched by debris. In addition, it is found that COF decreases with increasing load. Finally, the rapid wettability of the oil droplets on the flocking surface shows the great potential of the surface for lubrication and anti-friction. [ABSTRACT FROM AUTHOR]

Solid lubricant materials could be used in various extreme conditions owing to the excellent anti‐friction and ‐wear with the low friction coefficient and wear rate. Polyurethane (PU)‐based solid lubricants as one of the widely utilized composite materials had been well‐known by researchers all over the world. PU‐based composite lubricants were commonly segmented into single‐phase lubricants and multi‐phase lubricants via inorganic or organic lubricant additives. What is more, the modified PU by solid lubricants would endow higher tribological performances than that of single‐phase PU‐based lubricants. Based on the multi‐component synergy, the multi‐phase lubricants could significantly improve the PU matrix's lubrication and wear resistance and enhance the comprehensive performance such as corrosion resistance. This paper mainly discussed and summarized the recent development in tribological performances of PU‐based composite lubricants, and explored their prospective research directions. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are widely utilized in the biomedical sector, they still exhibit poor tribological properties and low wear resistance when employed against even weaker substances. The poor hardness, instability, high coefficient of friction, low load-carrying capacity, and insufficient resistance to not only abrasive but also adhesive wear are further disadvantages of titanium alloys. The focus of this investigation is on the tribological performance of Ti-6Al-4 V alloy in contact with WC carbide abrasive balls when subjected to nanodoped cooling and lubrication conditions. Tribological experiments were executed on Ti-6Al-4 V flat samples using a ball-on-flat tribometer in dry hybrid graphene/boron nitride combination nanoparticles (MQL, nano-3), nanographene with MQL (nano-1), and boron nitride with MQL (nano-2) conditions. After that, the most significant tribological characteristics were investigated, including volume loss, friction coefficient, wear rate, and micrographic structures. The outcomes also demonstrated that the hybrid nanoparticle situation experienced the least amount of volume loss. [ABSTRACT FROM AUTHOR]

Electrically as well as thermally conductive lubricants have drawn considerable attention and are an emerging research topic because they have unique advantages and advanced lubrication performance over traditional lubricants such as corrosion protection and efficient heat dissipation. For instance, some components of electric vehicles (EVs) such as bearings, seals, pads and gears require conductive lubricants to avoid premature failure and electromagnetic interference (EMI) problems due to induced shaft voltages and currents. This review provides a comprehensive overview of the recent developments in conductive lubricants. The review focuses on the important aspects to enhance the thermal and electrical conductivities as well as the tribological behavior (COF, and wear rate) of conductive solid, semisolid, and liquid lubricants. The lubricants that are electrically and thermally conductive with superior tribological performances have been identified through extensive literature review and presented in tabular form. This review summarizes the effect of various additives used to improve the conductive properties of the lubricants, such as polyalphaolefin oil, hydraulic oil, paraffin oil, and mineral oil. Furthermore, the review discusses the lubricating mechanism of conductive solid and liquid lubricants to facilitate a deeper understanding. Finally, the future perspectives and the research directions for conductive lubricants are also addressed. [ABSTRACT FROM AUTHOR]

The purpose of this work is to explore the mechanism of lubricants containing TiO2 nanoparticles to improve tribological properties and the effect of nanoparticle lubrication on precision forming. Firstly, the friction coefficients, wear rates, and average surface roughness for different concentration of TiO2 nanoparticle in lubricants are obtained from friction and wear tests. It is found that when the TiO2 concentration is 0.1wt%, the surface roughness of the sample reaches the lowest, while the surface roughness is higher under the lubricant of 0.5wt% nanoparticles which is ideal for friction coefficient and wear. Then, the effect of adhesion which mainly occurs when using lubricant containing no nanoparticles on the workpiece surface roughness is analyzed, including the joint action of height reduction of the micro-convex peak and the root roughening. Mechanism of lubricants containing TiO2 nanoparticles to improve tribological properties is presented, in which the wear and morphology evolution of workpiece surface are influenced by the coupling of tip adhesion and nanoparticle smoothing. Meanwhile the addition of nanoparticles can inhibit the adhesive wear of the tip, the effect of which is enhanced with the increase of TiO2 particle concentration. This explains why the surface roughness is higher and the friction coefficient and wear are minimal when the content of TiO2 nanoparticle is 0.5wt%. Finally, the effect of TiO2 nanoparticle lubrication on precision forming, including the metal flow, the forming load, and the error tolerance, is discussed. This work will help to further promote the development of precision forming technology. [ABSTRACT FROM AUTHOR]

Lubricant coating is an efficient method for preventing ice formation on the surface of wind turbine blades. However, lubricants are frequently lost during the freezing and deicing cycles, along with the migration of frost or ice. As a result, developing a lubricating anti-icing coating with high wear resistance and stability is critical for resolving the icing problem on fan blades. In this paper, 3-Aminopropyltriethoxysilane (KH-550) coupling agent was used to modify the nano-SiO2 particles to construct the micro-nano rough surface of the coating. Then, liquid paraffin lubricant was injected to obtain a new type of self-supplemented lubricating micro-nano composite coating, and its mechanical wear resistance and anti-icing performance were explored. The experimental results show that the contact angle of the liquid lubricating liquid micro-nano composite coating is still >105° and the sliding angle is <15° after 50 wear tests, showing good ice repellency, indicating that its wear resistance is enhanced. According to the standard ISO 2049, the mechanical adhesion reaches grade 0, showing good mechanical stability. The ice adhesion of the composite coating is 85.6% lower than that of the unlubricated sample, and the mechanical interlock between ice and the rough surface was greatly reduced. In comparison to the non-lubricating liquid coating, the micro-nano composite coating effectively extends the total freezing time of water droplets, reaching 821 s and demonstrating good anti-icing performance. [ABSTRACT FROM AUTHOR]

Lubricant coating is an efficient method for preventing ice formation on the surface of wind turbine blades. However, lubricants are frequently lost during the freezing and deicing cycles, along with the migration of frost or ice. As a result, developing a lubricating anti-icing coating with high wear resistance and stability is critical for resolving the icing problem on fan blades. In this paper, 3-Aminopropyltriethoxysilane (KH-550) coupling agent was used to modify the nano-SiO2 particles to construct the micro-nano rough surface of the coating. Then, liquid paraffin lubricant was injected to obtain a new type of self-supplemented lubricating micro-nano composite coating, and its mechanical wear resistance and anti-icing performance were explored. The experimental results show that the contact angle of the liquid lubricating liquid micro-nano composite coating is still >105° and the sliding angle is <15° after 50 wear tests, showing good ice repellency, indicating that its wear resistance is enhanced. According to the standard ISO 2049, the mechanical adhesion reaches grade 0, showing good mechanical stability. The ice adhesion of the composite coating is 85.6% lower than that of the unlubricated sample, and the mechanical interlock between ice and the rough surface was greatly reduced. In comparison to the non-lubricating liquid coating, the micro-nano composite coating effectively extends the total freezing time of water droplets, reaching 821 s and demonstrating good anti-icing performance. [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 friction and wear reducing properties of ammonium thiomolybdate as a water‐soluble lubricant additive were evaluated using a pin‐on‐disck tribometer on a steel‐steel contact. The tribological performance of aqueous solutions of thiomolybdate prepared at concentrations between 0.1 and 0.3 wt% Mo were evaluated at the same load (10 N), entrainment speed, sliding distance and temperature. Although there is a reduction of friction and wear compared with pure water, a significant difference is observed, depending on the additive concentration. SEM/EDAX and Raman spectroscopy analyses of the wear tracks of specimens tested at concentrations below 0.3 wt% Mo reveal the formation of FeS which is responsible for gradually reducing the coefficient of friction from values between 0.30 and 0.5 down to ~0.11. At 0.3 wt% Mo, the analyses indicated the formation of a MoS2 which keeps the coefficient of friction in ~0.05, the lowest recorded value. [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]

The results of a sliding wear tests on base and thermal treated gray cast iron (GCI) samples from internal combustion engine cylinder liner are reported here for dry and lubricated conditions. A thermal treatment was applied to samples of 10 x 10 mm to avoid the effect of residual stress and to obtain the microstructure of interest. Tribological tests were carried out up to 27000 cycles at room temperature. A frequency of 15 Hz, a stroke amplitude of 6 mm, and a maximum contact pressure of 1.12 GPa were selected. Under the unlubricated settings, a noticeable decrease in friction coefficient and specific wear rate are attributed to the appearance of irregular graphite nodules in the heating–quenching process. The significance of thermal treatment applied to low carbon cast iron in the derived self-lubricating function and its synergistic role with the oil lubricant is discussed. In this context, this work illustrates, for the first time, how the change in the morphology from flake graphite to irregular nodule graphite positively determines the reliability of gray casting irons. [ABSTRACT FROM AUTHOR]

The aeronautical industry constantly strives for efficient technologies to facilitate hole-making in CFRP/Ti6Al4V structural components. The prime challenge in this direction is excessive tool wear because of the different engineering properties of both materials. Nanofluid minimum quantity lubrication (NF-MQL) is the latest technology to provide synergistic improvement in tool tribological properties and lubrication function during machining. In the current study, an MoS2-based NF-MQL system was applied during helical milling using a FIREX-coated tool. In-depth analysis of wear, a scanning electron microscope (SEM), and electron deposition spectroscopy (EDS) were used to evaluate workpiece elemental transfer and tool wear mechanisms. Experimental findings showed that 1% nanoparticles concentration in lubricant resulted in low tool wear of 13 µm after 10 holes. The SEM and EDS analyses depicted formation of tribo-film on the surface, resulting less severe wear and a reduced degree of adhesion. However, a low nanoparticle concentration of 0.5% resulted in 106 µm tool wear after 10 holes with slight evidence of tribo-film. Parametric analysis based on eccentricity, spindle speeds (individual for CFRP and Ti6Al4V), axial pitch, and tangential feed showed correlations with mechanical damage. An extended study of up to 200 holes showed diffusion of C element at a high rate as compared to metal elements such as W and Co. The lowest tool wear was observed using eccentricity level 1, spindle speed Ti6Al4V 1000 rpm, spindle speed CFRP 7500 rpm, tangential feed 0.01 mm/tooth, axial pitch 1.5 mm, and 1% of MoS2 nanoparticles. [ABSTRACT FROM AUTHOR]

The hydrogenated amorphous carbon (a-C:H) film, which is widely used in the engineering field, has attracted more and more researchers' attention. A-C:H films exhibit super-low friction coefficient and low wear in inert atmospheres but high friction coefficient and wear in ambient air. In this study, 3D graphene and h-BN were used as solid lubricants to reduce the friction and wear of steel-a-C:H film contact conditions under different loads. When 0.01 wt% of 3D graphene and 0.1 wt% h-BN were mixed at a volume ratio of 1:1, the lubricating effect is optimum. Compared with a-C:H films, not only the friction coefficient is reduced, but also the wear rate is further reduced. This is mainly due to the formation of an ordered and dense transfer film on the sliding interface, which effectively prevents the direct contact between the surfaces of the friction pair. [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]

Based on the basic mechanism and bionics principle that texture affects the dynamic pressure effect of lubricating medium, a V-shaped texture that converges along the sliding direction is designed. Through numerical simulation, the optimal geometric parameters and distribution of the V-shaped and textures are obtained. A textured surface with various texture features is prepared using a nanosecond ultraviolet laser with bearing steel as substrate. Tribological experiments with friction and wear tester are performed to investigate the effect of characteristic parameters and distribution of surface texture on the lubrication performance and the lubrication properties are compared and analyzed with that of circular texture. Hence, this investigation provides a research direction to improve the lubrication performance between frictional pairs under fluid lubrication condition to reduce the frictional wear of mechanical systems. The results show that under the conditions of optimal parameters, due to the effect of convergence and extrusion on the flow of lubrication medium, the V-shape texture is better than the circular texture in improving the lubrication performance. The optimal characteristic parameters of V-shape texture are: 60° for the angle between the two wings, 0.53 for shape parameter, 25.9% for area ratio, 13 μm depth, 60% texture area coverage ratio, and the inlet of flow field of the texture distribution position. [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]

Purpose: WO3 particles were prepared by the sol-gel method. Tetraethyl silicate (TEOS) was used to obtain a SiO2-coated WO3 nanoparticle. Quantum chemical parameters of oleic acid, triethanolamine, glycerol and methyl pentane as dispersants were theoretically calculated. Tribological properties of SiO2/WO3 nanocomposite lubricant were carried out on an MRS-10A four-ball friction and wear tester. Design/methodology/approach: The purpose of this study is to investigate the preparation and tribological properties of SiO2/WO3 nanocomposite lubricant. Findings: The obtained SiO2-coated WO3 nanoparticle (nano-SiO2/WO3) with a particle size of about 70 nm. The calculated adsorption energy of triethanolamine on the surface of the steel ball is 554.6 eV, and triethanolamine is selected as the dispersant. The dispersion effect of SiO2/WO3 nanocomposite lubricant is good, which shows that triethanolamine oleate plays a good dispersion role in the preparation of lubricant, which is consistent with the calculation results of the adsorption capacity of dispersant. As a good auxiliary lubricant, SiO2 can improve the tribological properties and wear resistance of WO3. Originality/value: Nanocomposite lubricants have been the focus of research in recent years, which could greatly reduce energy consumption. And the SiO2/WO3 exhibited excellent lubrication performance as a lubricant additive. The lubrication mechanism of SiO2/WO3 nanocomposite lubricant is the synergistic lubrication mechanism of friction film lubrication and antifriction bearing. This study could provide a certain reference for the practical application of nanocomposite lubricants. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the influence of dimple textures on the friction and wear properties of tapered roller bearings (TRBs) with many pattern parameters, e.g. diameter, depth and area density under starved lubrication. Design/methodology/approach: The pattern parameters include the dimple diameter (D; 60, 100 and 200 µm), dimple depth (H; 5, 10 and 20 µm) and area density (S; 6%, 12% and 24%). Dimples were fabricated on the outer ring (OR) of TRBs using a laser marking machine. The tribological properties of dimple-textured TRBs under starved lubrication were studied on a vertical universal friction wear tester with special friction pairs. The effect mechanisms of dimple textures on the tribological properties of TRBs are presented and summarized through experiments and discussions. Findings: When dimple-textured TRBs revolve under starved lubrication, the average coefficients of friction (ACOF) and wear losses are markedly lower than those of non-textured bearings. S has the greatest influence on the COF curve. When D is 100 µm and S is 24%, the ACOF and wear losses are both lowest, i.e. 0.00426 and 0.51 mg, respectively. Under the same test conditions, compared with the non-textured group, its COF and wear loss decreased by 35.6% and 62.5%, respectively. Originality/value: This work provides a useful reference for the research on the raceways of textured TRBs. [ABSTRACT FROM AUTHOR]

n the last few years, there is a general shift observable toward greener lubrication, fueled amongst others by policy initiatives such as the European Green Deal in consistency with the UN Sustainable Development Goals. At least 70 vol% of a lubricant is composed of a specific base oil, the rest is a variation of additives altering the lubricant properties (enhancing or suppressing existent base oil properties or adding new properties) to be operational for a particular field of application. So, in terms of sustainability, biodegradability, bioaccumulation, and toxicity the type of base oil plays a major role, which makes environmentally harmful petroleum-based lubricant formulations highly problematic for future applications. Hence, this leads to an ever-growing demand of environmentally friendly lubricant alternatives. Within the scope of this review lies the investigation of bio-based, bio-derived, and other sustainable lubricant components that could serve as promising replacements for conventional petroleum-based formulations, in accordance with the principles of green chemistry and tribology. As recycling is embraced by the term sustainability, waste-derived components of non-biological origin are also included in this work. An overview of studies on the tribological performance such as friction and wear properties of these sustainable and benign lubricant components is given. [ABSTRACT FROM AUTHOR]

Graphene is a single atomic plane of sp2-bound carbon that has attracted considerable interest in various technologies. On the basis of its unique physical, mechanical, and chemical properties, graphene is a potentially strong candidate as a lubricant additive in its liquid-based form to reduce friction and protect surfaces from degrading. Furthermore, graphene on wear performance acts as a heat dissipation source for liquid lubricants. This review explores and addresses the fundamental mechanisms illuminating the exceptional tribological behaviours of graphene family materials and their limitations. Although graphene additives were reported to improve friction coefficients and wear properties, several challenges remain a hindrance, such as production costs, dispersion stability, and lack of information regarding graphene optimisation. Thus, this review can provide a standard methodological framework for graphene additives in improving tribological performance. Moreover, this review provides an up-to-date review of current tribological experiments based on ultrafine particles incorporated with graphene as an additive for lubricating liquids. [ABSTRACT FROM AUTHOR]

In the study of wear behavior of tribo-pairs in reciprocating pumps, the tribo-pairs can be considered as contact pairs consisting of a disc and pin. In this paper, pin-on-disc wear tests were carried out by using two types of cast iron pin specimens with different materials. Additionally, the effects of the lubrication condition, test load, diamond-like carbon (DLC) coating and plateau honing cross-hatch pattern on wear behavior of the tribo-pairs were investigated. Experimental results based on surface topography analysis and scanning electron micrograph (SEM) analysis show that the lubricant and DLC coating have a positive effect on wear resistance of test specimens. Disc specimens of three material types (i.e. ISO 185/JL/250, tin-bronze, zirconia) are able to show good anti-wear behavior. The tribo-pairs composed of spheroidal graphite cast irons as well as implementation of the plateau honing cross hatch on disc specimens have no significant effect on the wear resistance. The Archard model was used to estimate abrasive wear under dry conditions, which was over-predicted compared to the experimental results. [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]

Self-lubricating coating is used to solve the problem of insufficient lubrication and failure of mechanical transmission parts at high temperature. In this work, we designed a NiCrAlY-Ag-SrF 2 coating through the synergistic lubricating effect of a novel SrF 2 lubricant and Ag, and the reinforcing action of in-situ formed oxides. The results showed that the NiCrAlY-Ag-10 wt% SrF 2 coatings have high bond strength (60 MPa) and hardness due to the low porosity and production of in-situ oxides. From room temperature (RT) to 900 °C, the friction coefficient and wear rate of the coating are 0.29 − 0.47 and 1.03 × 10−5 − 6.74 × 10−5 mm3/N·m, respectively. This reveals that SrF 2 can be employed as an alternative to high temperature lubricants, and the coatings achieve lubrication effect at a wide temperature range. • NiCrAlY-Ag-SrF 2 coatings were produced by detonation spraying method. • SrF 2 and in-situ oxides are employed to lubricate and strengthen the coatings. • NiCrAlY-Ag-SrF 2 coatings achieve lubrication from room temperature to 900 °C. • The synergistic effect of SrF 2 , Ag, and in-situ formed SrCrO 4 is responsible for the lubrication performance over a wide temperature range. [ABSTRACT FROM AUTHOR]

In this work, we showed that the mesoporous molecular sieve SBA‐15 could be used as an oil storage smart microcontainer to adsorb PAO6 oils and is prepared as an oil‐containing molecular sieve SBA‐15O, the compositing of SBA‐15O with unsaturated polyester resins (UPR) can significantly improve the lubrication properties of UPR. The oil‐containing molecular sieve SBA‐15O was prepared by vacuum impregnation and compounded into the UPR. The lubricating effect of different SBA‐15O contents on the UPR was investigated. As compared with the UPR, the coefficient of friction (COF) of the 10%SBA‐15O/UPR could be reduced to 10% of that without SBA‐15O, and the wear rate by three orders of magnitude. The results show that the improvement of lubricating performance is related to the release of lubricating oil from the microcontainer to the surface to produce a lubricating oil film during friction, thereby enhancing the self‐lubricating performance of the composite material. [ABSTRACT FROM AUTHOR]

An UHMWPE‐based multiscale composite containing graphene oxide, nanodiamonds, and short carbon fibres has shown excellent performance under distilled water lubrication. However, it is crucial to evaluate its tribological performance under conditions which more accurately represent the final application. In this study, the tribological performance of the developed UHMWPE‐based multiscale composite is evaluated and compared with neat UHMWPE under different lubricating conditions: no lubricant (dry), in seawater (SW) and in an environmentally acceptable lubricant (EAL). While neat UHMWPE displays a lower friction and wear in dry conditions, the multiscale composite performs better under SW and EAL lubrication. A maximum reduction in friction coefficient of 77% and specific wear rate of 88% are obtained in SW. Under EAL lubricated conditions, the multiscale composite has a maximum reduction in specific wear rate of up to 75%. [ABSTRACT FROM AUTHOR]

Ionic liquids have been widely discussed as potential lubricants, however, their properties make them also very good potential candidates as lubricant additives (e.g., friction modifiers and anti-wear). In this work, the tribological study of two ionic liquids (tributylmethylphosphonium dimethylphosphate (PP), and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP)) as lubricant additives has been performed on stainless steel (AISI 316L) exposed to polar (water-glycol) and non-polar (polyalphaolefin) based lubricants under boundary lubricating conditions. The performance of these ionic liquids as lubricant additives has been compared to a classical organic friction modifier (dodecanoic acid (C12)). The water-glycol lubricant formulated with the two ionic liquids showed friction values higher than the same base lubricant formulated with dodecanoic acid, however, opposite results were observed for polyalphaolefin (PAO). A detailed surface chemical analysis using X-ray photoelectron spectroscopy (XPS) revealed differences in the passive/tribofilm thickness and chemical composition of the stainless steel surface tested in all lubricants. In the case of the polar lubricant additivated with ionic liquids, the tribochemical reaction accompanied by a tribocorrosion process led to the formation of an unstable passive/tribofilm resulting in high friction and wear. However, in the absence of tribocorrosion process (polyalphaolefin base lubricant), the tribochemical reaction led to the formation of a stable passive/tribofilm resulting in low friction and wear. A detailed surface and subsurface investigation of the microstructure using scanning electron microscopy equipped with a focused ion beam (SEM-FIB) showed that high wear rates resulted in thicker recrystallization region under the wear track surface. Among all lubricant additives tested in this work, BMP in non-polar lubricant media showed the best tribological performance. [ABSTRACT FROM AUTHOR]

The tribological performance of GCr15 bearing steel under different lubrication conditions was investigated. The results showed that from lean lubrication to dry friction the tribological properties of GCr15 bearing steel change sharply and the wear mechanism transforms from abrasive wear to the mixture of adhesive wear and oxidation wear. Meanwhile, the thickness of the severe plastic deformation layer increases from lean lubrication to dry friction. The retained austenite transforms into the martensite on the worn surface and the residual compressive stress increases. The variation rate of friction coefficient (f′) and the time of the transition zone (△t) are proposed as the indicators of bearing early failure under unsteady lubrication, which are closely related to service conditions. [ABSTRACT FROM AUTHOR]

Metals currently have a wide range of applications in which friction creation is a serious issue. Wear rate increases as a result of constant friction, causing metal deformation. The Pin on Disc equipment was used to test sunflower oil and additives (biodiesel and ZnO). The impact of vegetable oil lubricant, its biodiesel, and nanoparticle added lubricant on the wear of metallic surfaces was investigated. There are seven more lubrication conditions in addition to the dry state. Raw sunflower oil, Raw oil (80 percent) + B20, Raw oil (60 percent) + B40, Raw oil (80 percent) + B20 + Nano1 (0.5 percent), Raw oil (60 percent) + B40 + Nano1 (0.5 percent), Raw oil (80 percent) + B20 + Nano2 (0.2 percent), Raw oil (60 percent) + B40 + Nano2 (0.2 percent), Raw oil (80 percent) + B20 + Nano2 (0.2 percent), Raw oil (60 percent) + B40 A stainless steel disc and a brass pin were utilised in this experiment. At three loads (1, 3 & 5 kgf) and three speeds (300, 500 & 700 rpm), the wear rate, frictional force, and coefficient of friction for all lubricants are examined. Nanoscale particles added to lubricants were proved to improve tribological characteristics significantly. In dry circumstances, the wear rate, frictional force, and coefficient of friction are all increased. Because the presence of ZnO nanoparticles reduces the wear rate, frictional force, and coefficient of friction greatly when compared to basic oil and dry circumstances, nano lubricant has the lowest value. [ABSTRACT FROM AUTHOR]