Formation Of Lubricating Film Research Articles

Effect of Surface Texturing on Friction and Lubrication of Ti6Al4V Biomaterials for Joint Implants

The number of endoprosthetic implants for both large and small joints is increasing at a steady rate, thereby creating a growing demand for durable products that closely replicate the functionality of human joints. Notwithstanding the aforementioned advancements, challenges pertaining to implant fixation and tribological surfaces persist. The advent of progressive technologies, such as three-dimensional printing, offers a promising avenue for addressing these challenges in implant design and surface engineering. The Ti6Al4V and CoCrMo alloys, renowned for their biocompatibility and osseointegration properties, represent promising printable materials, although they are susceptible to wear on articulating surfaces. In order to mitigate the effects of abrasion, it is essential to implement surface treatments to facilitate the formation of a robust lubricating film. This research investigates the potential of texturing and electrochemical polishing to enhance protein aggregation in the contact area. The study employs a reciprocating simulator and colorimetric interferometry to observe the contact area and measure the coefficient of friction (CoF) of modified surfaces. The findings demonstrate that textured surfaces and the combination of electrochemical polishing result in an increase in the thickness of the protein lubrication film, which may potentially reduce wear. These outcomes suggest the potential for the utilization of Ti6Al4V alloy implants with fewer elements manufactured by additive technology.Graphical

Dispersion and Tribological Behaviors of Modified Functionalized Surfaces of Single and Hybrid Nanoparticles in Water-Based Lubrication

This study investigated the dispersion and tribological effetcs of modifying surface functionalization on single (GO, Al2O3, MgO, SiC) and hybrid (SiC/MgO, Al2O3/MgO) nanoparticles in water-based lubricant (WBL) formulations. Polyvinylpyrrolidone (PVP) and glycerol were utilized to further enhance dispersion and viscosity. The experimental findings revealed that incorporating modified nanoparticles surfaces in WBLs improved hydrophilicity and dispersion by introducing additional oxygen functional groups. This effectively reduced direct metal-to-metal contact, resulting in lower interface temperatures and enhanced tribological performance. Hybrid Al2O3/MgO nanoparticles exhibited a significant 76.69 percent enhancement in tribological performance in wear mechanisms, synergistically filling microcracks to improve lubricant film formation, bearing, and mending effects. Using a single nanoparticle was found to be insufficient for achieving enhanced tribological effects. All nanoparticles improved bearing effects, except for GO, which promoted a shearing effect. High-hardness nanoparticles such as SiC and Al2O3 demonstrated an additional polishing effect.

Effects of contact path on lubricant distribution and EHL film formation

Effects of contact path on lubricant distribution and EHL film formation

Effect of bionic shield texture on friction behavior of silicon carbide under water lubrication condition

Abstract Reasonable texture parameters can effectively generate local dynamic pressure effects and promote the formation of lubrication film. The synergistic friction reduction mechanism of the shield-shaped texture on the Silicon Carbide (SiC) surface under water-based lubrication conditions between the flow pressure effect and the ‘rolling ball’ effect is investigated by combining simulation analysis and friction experiments. The effects of shield textured surface on the friction and wear characteristics of SiC surface and the characteristics of interfacial polarization electric field under different rotational speeds and different load conditions were analyzed. The results display that synergistic texture lubrication has a beneficial effect on improving tribological properties. The surface with 6% texture area occupancy showed the best tribological characteristics. The surface with a textured area occupancy of 6% displays the optimal tribological properties. Moreover, the friction reduction mechanisms under different working conditions are discussed, with the textured uniformly arranged surfaces being more suitable for high-speed and heavy load (140 N, 2000 rpm) conditions and the textured non-uniformly arranged surfaces being more suitable for low-speed and light load (40 N, 400 rpm) conditions.

PDA Nanoparticle-Induced Lubricating Film Formation in Marine Environments: An Active Approach

The low viscosity of water-lubricated films compromises their load-bearing capacity, posing challenges for practical application. Enhancing the lubrication stability of these films under load is critical for the successful use of seawater-lubricated bearings in engineering. Polydopamine (PDA) shows great potential to address this issue due to its strong bio-inspired adhesion and hydration lubrication properties. Thus, PDA nanoparticles and seawater suspensions were synthesized to promote adhesive lubricating film formation under dynamic friction. The lubrication properties of PDA suspensions were evaluated on Cu ball and ultra-high molecular weight polyethylene (UHMWPE) tribo-pairs, with a detailed comparison to seawater. The results show PDA nanoparticles provide excellent adhesion and lubrication, enhancing the formation of lubricating films during friction with seawater. Under identical conditions, PDA suspensions demonstrated the lowest friction coefficient and minimal wear. At 3 N, friction decreased by 56% and wear by 47% compared to distilled water. These findings suggest a novel strategy for using PDA as a lubricant in seawater for engineering applications.

Multifunctional Ti3C2Tx-based epoxy composite coating towards intelligent response and corrosion/wear resistance

Questions remain about the unreasonable collocation of Ti3C2Tx and nanocontainers resulting in the performance degradation of multi-function Ti3C2Tx-based epoxy composite coating. Here, mesoporous SiO2 nanocontainers (SNT) containing both potassium thiocyanate and hexadecyl trimethyl ammonium bromide (CTAB) were loaded on MXene-based platform (SNT-on-MP) to achieve a novel epoxy coating (SNT-on-MP@EP) with the integrated functions of self-warning, self-healing, anti-corrosion and anti-wear. In the damaged area, the thiocyanate groups combined with Fe3+ ions to form a blood-red color display, and the formed coordination compound and CTAB as corrosion inhibitors were deposited on the metal substrate, thus showing intelligent response function. Besides, because of passive and active synergistic protection functions, the lowest-frequency impedance value of SNT-on-MP@EP maintained 5.74 × 107 Ω·cm2 after 4 weeks of exposure in salt water environment, which was increased by two orders of magnitude compared with pure epoxy coating. Under the reciprocating sliding friction, the wear rate of SNT-on-MP@EP reached 5.32 × 10−5 mm3/N·m, and was reduced by 58.29 %, owing to the formation of lubricant film at the friction interface and the enhancement of the deformation resistance of the coating. The reasonable collocation of SNT and Ti3C2Tx-based platform eliminated the problem of weak interaction between traditional inorganic nanocontainer and water-based epoxy coating, thus giving full play to the advantages of both.

Synthesis and Performance Evaluation of High-Temperature-Resistant Extreme-Pressure Lubricants for a Water-Based Drilling Fluid Gel System.

Addressing the high friction and torque challenges encountered in drilling processes for high-displacement wells, horizontal wells, and directional wells, we successfully synthesized OAG, a high-temperature and high-salinity drilling fluid lubricant, using materials such as oleic acid and glycerol. OAG was characterized through Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The research findings demonstrate the excellent lubricating performance of OAG under high-temperature and high-salinity conditions. After adding 1.0% OAG to a 4% freshwater-based slurry, the adhesion coefficient of the mud cake decreased to 0.0437, and at a dosage of 1.5%, the lubrication coefficient was 0.032, resulting in a reduction rate of 94.1% in the lubrication coefficient. After heating at 200 °C for 16 h, the reduction rate of the lubrication coefficient reached 93.6%. Even under 35% NaCl conditions, the reduction rate of the lubrication coefficient remained at 80.3%, indicating excellent lubrication retention performance. The lubricant OAG exhibits good compatibility with high-density drilling fluid gel systems, maintaining their rheological properties after heating at 200 °C and reducing filtration loss. The lubrication mechanism analysis indicates that OAG can effectively adsorb onto the surface of N80 steel sheets. The contact angle of the steel sheets increased from 41.9° to 83.3° before and after hot rolling, indicating a significant enhancement in hydrophobicity. This enhancement is primarily attributed to the formation of an extreme-pressure lubricating film through chemical reactions of OAG on the metal surface. Consequently, this film markedly reduces the friction between the drilling tools and the wellbore rocks, thereby enhancing lubrication performance and providing valuable guidance for constructing high-density water-based drilling fluid gel systems.

Investigation of tribological performance of the ultra-dispersive TBC-CNTs as additives for aqueous lubrication

Carbon nanotubes (CNTs), as water-based additives, are potential candidates for reducing friction and wear whereas the weak dispersion stability impedes their application in aqueous lubrication. Therefore, CNTs were functionally modified by 4-tert-butylcatechol (TBC) nucleophilic for synthesizing the ultra-dispersive TBC-CNTs. The particle sizes and dispersibility of TBC-CNTs in water were investigated. It was found that particle sizes of the most of CNTs were reduced after modification and 0.035 wt% TBC-CNTs remained uniformly dispersed in water for 2 months. The lubrication behavior of TBC-CNTs as water-based additives for ceramic/steel tribo-pairs was investigated by using a ball-on-disc apparatus. Notably, the optimum concentration of TBC-CNTs was determined 0.2 wt% that contributed to 30.6 % of friction reduction and 28.3 % of wear resistance, respectively, at 0.6 m/s and 8 N. The tiny structure of TBC-CNTs contributed to their entrance into the contact interface and playing lubricating roles. Furtherly, the increase of water film thickness within contacts and formation of lubrication film on rubbing surfaces caused by TBC-CNTs addition resulted in the friction and wear reduction.

EHD simulation study on the influence of measured ICE compression piston ring profiles on the lubrication film formation

In this simulation-based research, the authors investigate the influence of the contacting profile and its tilting orientation of original compression piston rings on their hydrodynamic properties in internal combustion engines (ICEs). They employ a systematic approach, detailing the computational framework and simulation parameters. Three different original piston rings belonged to the same engine are used for the simulation and corresponding experimental validation in this publication. Results and discussions highlight the directional dependence of hydrodynamic conditions, with distinct differences for individual rings. Original smoothed profiles are compared with substitute geometries like quadratic parabola and circular arc fits. The research contributes insights into the complex dynamics of compression rings in ICEs, providing a foundation for optimizing ring profiles for enhanced hydrodynamic properties.

Influence of CePO4 on high temperature anti-friction and anti-wear behaviors of nickel-based h-BN composite coatings

Solid lubricating coatings which offer and maintain anti-friction and anti-wear are urging to develop in the advanced technology applications over a wide range of temperatures. The h-BN composite coatings on the Inconel X750 superalloy is prepared by spark plasma sintering (SPS) technology to obtain low friction and wear over a broad temperature ranging from room temperature (RT) to 800 °C using a high temperature rotary tribometer. The influence of the contents of h-BN and CePO4 powders of the tribological properties of the composite coatings was studied systemically under different temperatures. The experimental results show that the composite coatings with 20 wt% h-BN show excellent high temperature anti-friction behaviors. Coefficient of friction (CoF) of the composite coatings with 20 wt% h-BN with CePO4 powder is lowest about 0.12 among the composite coatings at 800 °C. The CePO4 powders are helpful to improve the sintering behaviors and reduce the wear rate of the composite coatings at elevated temperature. The synergistic lubrication mechanism of h-BN and CePO4 of the composite coatings are investigated systematically. The high temperature anti-friction and anti-wear mechanism of the composite coatings is due to the formation of a layered gradient lubrication film on the worn surface.

Lubricating properties of thymol-based deep eutectic solvents

PurposeThis study aims to prepare thymol-based deep eutectic solvents (DESs) and use them as lubricates for friction and wear tests to simulate the wear conditions of hybrid bearings.Design/methodology/approachThrough the characterization and analysis of the morphology of wear scars and the elemental composition of friction films, the tribological behavior and wear mechanism of sample materials as lubricants were investigated and the anti-wear mechanism of thymol-based DESs was discussed.FindingsThe findings demonstrate that because of the formation of a fluid lubrication film and excellent kinematic viscosity, the lubrication effect of the prepared DES is improved by about 50% compared to the base lubricating oil. The prepared [Ch]Cl-thymol DES has a better anti-friction and lubrication effect than citric-thymol, EG-thymol and urea-thymol DESs, with an average friction coefficient of about 0.04.Originality/valueIn this work, the friction reduction properties of thymol-based DESs were studied as lubricants for the first time, and the lubrication mechanism of sample materials was investigated.

In-situ surface modified water-soluble Cu nanoparticles as lubrication additives in water-based cutting fluids

Water-based lubricants are essential in the field of tribology, and the application of nanoparticles as additives in water-based lubricants shows promise and significant practical importance. In this study, water-soluble Cu nanoparticles modified with methoxypolyethyleneglycol xanthate long-chain polymers were fabricated by a in-situ surface modification method. The tribological behavior of the Cu nanoparticles synthesized as additives in a water-PEG system was evaluated using a universal micro-tribotester. It was found that the synthesized nanoparticles could be stably dispersed in the water-PEG system and could enhance the tribological properties and load-carrying capacity of the system significantly. For example, the coefficient of friction could be reduced to 0.052, and the PB value increased to 588 N when the Cu nanoparticles were added at a mass fraction of 1.5 %. This was mainly attributed to the formation of a boundary lubrication film consisting of Cu, Fe2O3, Fe2(SO4)3, and FeS throughout the entire friction process. The boundary film effectively prevents direct contact between the friction surfaces, thereby improving the tribological properties. The incorporation of Cu nanoparticles as additives into commercial cutting fluids resulted in a lower coefficient of friction and significantly enhanced the extreme pressure performance of the cutting fluids, demonstrating promising application prospects.

The effect of MoS2 concentration on the thickness and tribology performance of electro-codeposited Ni–Cr–MoS2 coatings

A Ni–Cr–MoS2 coating with trivalent Cr was prepared on the surface of the cylinder liner by the composite co-deposition method to modify its tribology performance. The effects of MoS2 concentration on the properties of the coatings and tribological properties of cylinder liners were studied by surface detection methods and reciprocating wear tests. The results show that Ni–Cr–MoS2 coating has a smaller grain size, higher micro-hardness, and greater coating thickness, compared with Ni–Cr coating. Doping by MoS2 effectively reduces the friction coefficient of Ni–Cr coating from 0.142 to 0.107, the wear amount of coating decreases from 7.9 mg to 7.1 mg, and the scuffing time increases from 19 min to 56 min. It is found that the doping of MoS2 provided more nucleation sites and promoted the deposition of ions, which resulted in the refined grain and thicker coating. The formation of solid lubrication film by MoS2 during the wear process and more coating thickness are mainly responsible for the modification of the tribology performance of cylinder liners. This research provides a practical approach to prolong the service life of friction pairs.

Droplet migration through deformable stenosed microchannel: Dynamics and blockage

Understanding droplet migration in stenosed microchannels is crucial for various applications. This study explores how droplet properties (viscosity, surface tension, density, and diameter) and channel characteristics (stenosis degree and wall elasticity) affect droplet movement and blockage in deformable stenosed microchannels. Higher viscosities lead to lubrication film formation between droplet and wall, reducing viscous resistance, while increased surface tension enhances wall adherence, amplifying Laplace pressure. Droplet entry is primarily influenced by viscosity, while passage is governed by surface tension and curvature effects at the droplet–wall interface. Surface tension dominates pressure generation in the channel and within the droplet, influencing wall deformation and hydrodynamic resistance. The study examines the relationship among droplet viscosity, density, surface tension, channel wall elasticity, and the maximum capillary number (Camax) on the lubrication film thickness between the droplet and the channel wall. A lubrication film exists for Camax≥0.095, reducing blockage chances. A critical range of the modified Ohnesorge number Oh*×1000≤132 and the capillary number (Camax<0.095) indicates higher chances of droplet blockage. The blockage prediction method based on the modified Ohnesorge exhibits a sensitivity of 100%, specificity of 92.6%, and accuracy of 95.9%. Additionally, the study explores the impact of channel wall elasticity on droplet entry, transit, and hydrodynamic resistance. Higher wall elasticity facilitates faster entry but introduces curvature during passage, increasing frictional resistance and blockage likelihood as the wall softens.

Ultra-low friction system using special wetting interfaces: Bridging across various wetting regimes

Friction was the main way of energy loss in society, and reducing friction has become a focal point in current research. Inspired by special wetting phenomena, an asymmetric multiphase composite (AMPC) friction system was constructed. Tribological behavior of the friction system was evaluated using hydrogel on anodized aluminum as friction pair and superhydrophobic alumina with micro/nano-composite as substrate. Ultra-low friction coefficients (∼10−3) were measured under both Cassie and Wenzel regimes. Especially in Wenzel state, increased contact stress or extended shear rate promoted the formation of transfer lubricant film, thus enabling the ultra-low friction coefficient. Moreover, the system showed mechanical stability during prolonged water lubrication. This novel lubrication approach may provide valuable scientific solutions for specific tribology applications.

Impact of grease physical properties on the friction torque and service life of wheel bearings

Wheel bearings play a crucial role in ensuring the smooth and reliable rotation of wheels in automotive applications. Grease is commonly used as a lubricant in wheel bearings. The physical properties of grease, such as viscosity, base oil type, and thickener composition, significantly influence the overall performance and longevity of wheel bearings. This study investigates the impact of grease's physical properties on wheel bearing friction torque and service life. To evaluate the effects of different grease formulations, a series of experiments were conducted using a four-ball tester, rheometer, and a custom-built test rig to measure bearing frictional torque and service life. Multiple greases with varying viscosity grades, base oil types (mineral oil, synthetic oil), and thickener compositions (lithium, diurea, and polyurea) were tested under controlled operating conditions. Friction torque measurements were obtained using a high-accuracy torque sensor, while service life was determined by monitoring the bearing life in actual endurance testing. The results indicated that grease physical properties directly affected wheel bearing friction torque and service life. Low to Medium-viscosity greases generally exhibited 35–40% lower friction torque due to enhanced lubrication film formation and reduced metal-to-metal contact however, excessively high viscosity resulted in 50–60% higher frictional torque and thereby increased energy consumption. Different base oil types showed varying friction reduction and service life level, with mineral oil in some cases showed lower frictional torque around 30–40% particularly at high temperature but with significant reduction in the service life. Furthermore, the thickener composition significantly influenced grease performance. Based on these findings, selecting the appropriate grease with optimal physical properties is crucial for minimizing friction torque and extending the service life of wheel bearings.

Investigation of Graphene Platelet-Based Dry Lubricating Film Formation in Tribological Contacts

Dry lubricants used in highly loaded rolling bearings are in the focus of current research. In previous studies, graphene platelets applied as dry lubricants on the surfaces of angular contact ball bearings demonstrated superior properties. These specific bearings, experiencing both rolling and spinning motion, create more severe conditions for dry lubricants. To gain deeper insights into the lubrication effects, micro-tribological studies were carried out on the respective film formation and running behavior effects. In the tests, a fixed steel ball slid against an oscillating counterpart under a defined load. During the measurements, the applied load and tangential forces on the ball were recorded to calculate the friction. Comparative investigations included nano-graphite particles and fullerene as dry lubricants, in addition to graphene platelets of various staple thicknesses. To increase the adhesion of the films to the surfaces, a pre-rolling process was implemented. Afterwards, the friction on the compressed films was measured. The results indicate that the pre-rolling process effectively reduces the friction of the system. After testing, the surfaces underwent analysis using laser scanning microscopy to assess the formed films, wear, and material transfer. It has been demonstrated that the pre-rolling process leads to the formation of a very thin compacted film with surface protective properties. With the ball as a counterpart, the graphene platelets generate a transfer film on the contacting surface.

Effects of Oil and Solid Body Temperatures on Elastohydrodynamic Lubrication Film Formation

The present study focuses on investigating the influence of oil and solid body temperatures on elastohydrodynamic lubrication (EHL) film formation. Experimental and numerical simulation methods are employed to examine three heating methods: oil and ball heating, disc heating, and entire system heating. A preliminary comparison between the measured results and numerical simulations confirms the impact of heating methods on film formation while validating the availability of the numerical models. Further numerical analysis reveals that in the case of oil and ball heating, the temperature gradient induced by differences in solid body temperatures plays a more significant role in film formation compared to the conventional thermal-viscosity wedge effect caused by EHL film shear. This effect is further amplified at large sliding–rolling ratios and in steel–steel contacts. The overall film formation is primarily governed by the oil inlet temperature, whereas local film formation characterized by a dimple shape is influenced by both thermal gradient effects and thermal-viscosity wedge effects. This study provides valuable insights for selecting appropriate heating methods in experiments as well as understanding how temperature differences affect film formation in practical engineering.

Tribological Behavior and Mechanism of Surface-Modified Mullite as Polyurea Grease Additive

Abstract The excellent tribological performance of nanoparticles as additives in lubricating greases has attracted widespread attention. In this study, a silane coupling agent (KH550) was used to chemically modify nanoscale mullite (composed of Al2O3 and SiO2), and the modified nano-KH-mullite was dispersed as an additive in polyurea grease at different ratios (0.01, 0.05, 0.07, 0.1, and 0.3 wt%). The friction and wear performance of the compound polyurea greases were evaluated using a four-ball friction tester. Professional instruments will be utilized to analyze the micro-morphology, 3D profile, elemental content, and valence state of the worn surface, aiming to investigate the lubrication and antiwear mechanism of the nano-KH-mullite additive. The results indicate that nano-mullite effectively improves the antiwear and antifriction performance of the polyurea grease. When the additional content is 0.05 wt%, the friction coefficient (COF) and the wear scar diameter (WSD) are reduced by approximately 19.97% and 11.1%, respectively, and the roughness of the worn surface is also reduced. The excellent tribological performance of the composite grease is attributed not only to the good dispersibility of KH-mullite but also to its ability to promote the formation of a composite lubrication film on the friction pair surface. The component KH-Al2O3 in the KH-mullite can fill and repair scratches and grooves on the worn surface, while the other component KH-SiO2 can bear the load and convert the friction mode to rolling friction.

Diagnosis and root cause analysis of bearing failure using vibration analysis techniques

This paper is presented to diagnose and root cause analysis of the bearing failure. For this purpose, a vibration investigation was carried out on a motor with a 2300 kW power, 1489 rpm speed. Bearing failure was diagnosed by trending and analyzing vibration parameters. By investigating the bearing damage morphologies, a false brinelling pattern was observed. To find the failure cause, the machine was evaluated for two aspects; vibrations and lubrication. The resonance in the fan and the lack of full lubrication film formation were considered root causes of failure. To mitigate resonance, changing the operating speed was considered as a corrective action. By increasing the operating speed (1491 to 1530), the vibration amplitude decreased by nearly 21%. Also, the thickness of the lubricating film was improved by installing an airflow hose. Using this method, the time between failures increased from 3 to 11 months.