Imrpved Lubricant Film Strength Under Extreme Load Conditions

A lubricating grease additive comprising PAEK particles with a particle size D50 of up to 20 µm, wherein the PAEK particles are dispersed in a lubricating grease to improve tribological properties, particularly coefficient of friction, wear, and lubrication life, in non-metallic surface contacts.

Source

In the quest for sustainable lubrication solutions, the present research explored the potential of five organic compounds as additives in castor oil (CO) to improve its lubricating properties. The compounds tested were curcumin, eugenol, 1,3-Diphenyl-2-propanone, 1,3-Diphenyl-2-propenone, and 1,3-Diphenyl-1,3-propanedione. The main results showed that each additive enhanced at least one characteristic of CO. Most of the additives lowered the density of the castor oil but increased the viscosity by up to 20%. Curcumin and eugenol were particularly effective in creating thicker lubricant films and higher film thickness ratios. Eugenol and 1,3-Diphenyl-2-propanone significantly reduced the friction coefficient by up to 25%. Wear rate and wear mechanisms were significantly reduced with all the additives, achieving a reduction in wear rate of up to 50% (CO+curcumin). All the additives, except the 1,3-Diphenyl-1,3-propanedione, enhanced the oxidation onset temperature up to 8 C. The influence of chemical structure was also addressed. The optimal additive combination for a specific applica... Read More

Source

Abstract The bearing cage played a pivotal role in affecting the lubricant redistribution and lubrication states. In this study, a cage unit is incorporated into an optical ball-on-disc apparatus for the purpose of a quantitative study of cage-induced lubrication phenomena. It is found that the presence of the lubricant layer on the ball surface, shaped by the cage, affects the inlet lubricant supply of contact between the ball and the glass disc. Thereafter, the oil reservoirs surrounding the contact area and the film thickness were measured. The results showed that the lubricant reservoirs and inlet lubricant supplement were significantly improved with the employment of the cages. In addition, the lubrication state transformed from starved to fully flooded, effectively enhancing the lubrication state. Moreover, the lubricant on the steel ball surface moved from the side bands to the central rolling track, indicating that the lubricant redistribution was the main reason for the lubricating enhancement. Notably, the groove modification on the inner surface of the cage pocket facilita... Read More

Source

Abstract Journal bearing operation particularly in regard to marine applications is significantly affected by the performance of the most critical operational factors. Specifically, the lubricating oil film within journal bearing is so often than not subject to hazardous deterioration and ultimate failure in real operating conditions. Considering such fact, the current study is intended to carry out a literature survey regarding the efforts towards enhanced journal bearing performance based on proper selection of geometrical design for journal bearing. The aggregated data were thoroughly analyzed and assessed utilizing experimental, theoretical as well as numerical means. The outcomes derived from the conducted review represent firm grounds for carrying out extensive modifications into journal bearing design for marine applications. Further, such data will possibly be employed in future research investigations to extend the capability of journal bearing and its functions to attain the most possible enhanced performance in actual operating conditions. Apparently, the vast majority of ... Read More

Source

Solid lubricants are those materials that are used to lubricate mainly in dry circumstances. Its main role is similar to that of oils and greases, which is used to create a continuous and adherent lubricant film on the tribological pair surfaces for minimising friction and wear [1]. These coatings are typically employed in situations where liquid lubricants cannot be used or do not offer expected lubrication, such as in high or cryogenic temperatures, high vacuum, ultrahigh-radiation, reactive environments and in extreme contact pressure conditions [2]. Different types of solid lubricants, including graphite, have been extensively used since the middle of the 20th century [3]. From 1950 onwards, development in aeronautics industries emphasised the research and development of advanced solid lubricants. They can be classed based on their crystalline structure, features, properties, or functions, among other things. Different types of solid lubricant coating are shown in Fig. 1 [1].

Source

An anti-wear and anti-friction lubricating oil additive comprising malic acid, fatty alcohol, malic acid ester, and maleic acid ester, wherein the additive generates graphite-like carbon structures in situ at the friction contact interface to reduce friction coefficient and wear. The additive can be formulated with malic acid (0.5-20 wt%), fatty alcohol (5-50 wt%), malic acid ester (0.1-80 wt%), and maleic acid ester (0.2-50 wt%). The additive can be prepared by ultrasonication or stirring with a lubricating oil base oil.

Source

Grease composition with excellent extreme pressure (EP) properties, comprising a compound with a phosphate ester moiety in its molecular structure, for use in applications requiring wear resistance such as bearings, gears, and industrial machinery.

Source

Abstract Nonrenewable energy has produced abundant waste during tribological applications because a large portion of energy has been consumed to overcome friction and wear. Solid lubricants have recently aroused significant interest due to their defined friction and wear properties. Despite enormous efforts on solid lubricants, their important contributions to coatings, bulk materials, oil/grease, and super-lubricity have not yet been fully evaluated. This paper discusses in detail the present status of solid lubricants as effective reinforcements in tribology. It begins with the introduction of various descriptions and advanced structures of solid lubricants. Afterwards, it discussed their applications on improving friction properties in coatings and bulk materials. Additionally, lubrication mechanisms of solid lubricants in oil/grease are highlighted, followed by the detailed discussion of super-lubricity for solid lubricants. Finally, this review concludes final outlooks on the main challenges and future directions in this key area.

Source

The development of environmentally friendly and cost-effective lubricating materials to reduce friction and wear at macroscale is crucial for reducing fuel consumption and exhaust emissions, thereby enhancing sustainability. Deep eutectic...

Source

The influence of tuned surface wettability on the oil film building in a hydrodynamically lubricated contact under limited lubricant supply was investigated in this study. The thickness of the oil film was measured for three surface wettability combinations, OD & OS, AFD & OS, and AFD & AFS. The results indicate that the AFD & AFS combination maintains the largest oil film thickness. This enhanced performance is owing to the oil's non-wetting behavior on the AFD & AFS surfaces, which promote more lubricant supply at the slider inlet. Moreover, the oil accumulates at the inlet in the form of convex reservoir so that positive Laplace pressure is generated, which effectively bears part of the load and the film thickness increases.

Source

Rapid advances in modern industrial tribo-systems under high temperatures and heavy loads generate a growing demand for lubricating materials used in extreme environmental conditions. Metal-based lubricant coatings with excellent mechanical properties and thermal stability are widely used on core parts to reduce friction in harsh environments. This paper reviews the progress on modulating the frictional properties of coatings by designing the components and preparation techniques to prolong the lifetime of metal-based lubrication coatings. The impacts of the microstructural changes on the mechanical performances, including hardness, plasticity, interfacial adhesion, and environmental stability, were essential for the deformation and crack propagation of the coatings. Their performances and lubrication mechanisms were concerned under heavy loads, in a wide range of temperatures, and in corrosive marine environments. Finally, the study concluded the basic requirements of metal-based coatings for extreme environments at this stage. The research challenges and potential problems of metal... Read More

Source

Abstract A renewed interest in elastohydrodynamic lubrication (EHL) phenomena at high speeds, for which thermal effects strongly influence both traction and film thickness, has grown out of the challenges presented by high-speed geared transmissions in electric vehicles. This study uses a new ball-on-disc set-up employing the well-known ultra-thin-film interferometry technique to simultaneously measure EHL film thickness and traction at entrainment speeds up to 20 m/s and slide-roll ratios up to 100%. The effect of fluid composition is examined for Group I, II and III mineral oils, for two polyalphaolefins in Group IV, and for the traction fluid Santotrac 50. The effect of viscosity in the range 4180 mPa.s is investigated by varying bulk fluid temperature. At high speeds, both film thickness and traction are considerably lower than predicted by conventional EHL theory. The contact is seen to be fully-flooded for all conditions tested. The widely-used thermal EHL correction of Gupta is shown to overcorrect for the film thickness reduction even at modest SRRs. Finally, the influence o... Read More

Source

Lubrication technology plays a key role in solving tribological problems in engineered structural systems, and this technology has become a focus of research in order to enhance the efficiency and lifetime of the system. This review integrates the mechanism and the effect of many factors, such as surface charge, surface morphology, temperature, humidity, acidity, and fluid properties, on the lubrication performance enhancement by triboelectricity-controlled fluid attached to the coupled surface. Additionally, this review discusses methods for improving the lubrication performance of solid-liquid surfaces. Finally puts forward some future prospects on the lubrication performance enhancement by triboelectricity-controlled fluid attached to the coupled surface.

Source

Understanding the relevance and significance of the various replenishment mechanisms in grease-lubricated bearings is very important in choosing the appropriate lubrication strategy. This study shows that the lubricant film thickness in the ball-ring contacts of a deep groove ball bearing may increase by 10%25% due to vibrations. The possible mechanisms behind this film thickness increase are discussed. Of the proposed contact replenishment mechanisms, the micro-lateral motion of the contact edge across the tracks caused by in-operation vibrations appears crucial. Results show that in the starved contacts, vibration plays a vital role in determining the film thickness.

Source

Solid-liquid composite lubrication coatings provide highly reliable and long-lasting solutions to friction, wear, and lubrication problems in extremely harsh environments. Herein, a novel type of solid-liquid composite lubrication coating with a high load-bearing capacity and long service life was constructed by introducing epoxy resin containing lubricating oil into inherent defects of thermally sprayed ceramic coatings. Compared with conventional ceramic coatings, the hybrid coatings exhibited an 80.5 % reduction in the coefficient of friction to 0.15 and a decrease in the specific wear rate from 2.69 104 mm3N1m1 to 3.86 108 mm3N1m1. The low friction and wear of the composite coating were mainly attributed to the formation of a well-covered lubrication film consisting of PFPE, epoxy resin, Al2O3, and ZrO2 during the friction of the composite coating. This paper presented a novel approach to preparing new solid-liquid composite lubricating coatings that using unavoidable defects in thermal sprayed ceramic coatings to introduce a lubricating phase.

Source

Solid lubricants are crucial for industries operating at temperatures beyond 300 C, where liquid lubricants encounter limitations. Diamond-like carbon (DLC) films, known for exceptional solid lubrication and mechanical properties, need higher thermal stability for effective use in high-temperature applications. This study focuses on developing DLC films with the required thermal stability and solid lubricating properties. Hydrogen-free and hydrogenated DLC films were deposited utilizing deep oscillation magnetron sputtering (DOMS). Thermal characterizations revealed both films surpassed 500 C in thermal stability, rendering them suitable for high-temperature tribological applications. However, the hydrogenated DLC film exhibited superior solid lubricating properties, achieving an ultra-low friction coefficient below 0.05 at elevated temperatures, along with enhanced wear resistance, while effectively protecting its counterpart up to 500 C.

Source

This manuscript developed a novel DLCsupramolecular gel (HTG) composite lubrication system to achieve long-life outstanding lubrication under extreme contact stress while avoiding sealing challenges relying on the unique thixotropic properties of the gel. DLCHTG exhibited ultra-low wear and excellent friction reduction performance under a maximum contact stress of 2.24 GPa. DLC films with designed double transition layers possess high interfacial bond strength and mechanical properties, providing the basis for high wear resistance. The establishment of a robust tribofilm and the confinment effect of HTG on wear debris dominate the achievement of ultra-low wear. This ultra-low wear sliding extends the service life of the lubrication system with the broad implications for mechanical engineering, transportation, and wind power generation.

Source

Abstract The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy- and resource-efficient drivetrains. Water-containing lubricants like glycerol and polyalkylene glycols have shown great potential in achieving friction within the superlubricity regime with coefficients of friction lower than 0.01 under elastohydrodynamic lubrication. Additionally, a bio-based production of the base stocks can lead to the development of green lubricants. However, one challenge associated with the application of water-containing lubricants to gearboxes is the evaporation of water and its impact on the lubricant properties. In this study, the influence of water evaporation on elastohydrodynamic friction and film thickness was investigated for three water-containing polyalkylene glycols. Two nominal water contents of 20 wt% and 40 wt% and two viscosities were considered. The results show that the friction increases continuously with higher evaporated water content, while the overall friction level remains low in nearly water-free states. A similar ... Read More

Source

Abstract Today, mineral or synthetic oils that are made out of fossil raw materials, are the most common lubricants in gear drive applications. Most of them are non-biodegradable and may pose a risk to the environment. An important step to minimize the risk and the ecological footprint is the use of biodegradable and eco-friendly lubricants. Former research shows the potential of water-based lubricants in gear applications. Therefore, an oil-free, water-based lubricant, was developed for this study. The base lubricant contains plant-based thickeners to generate an appropriate viscosity for a sufficient lubricant film thickness in the tooth contact. In experimental investigations, the sliding wear and scuffing performance has been examined under variation of the added polymers and additives. The scuffing tests A/8.3/RT are performed acc. to DIN ISO 14635-1. The wear tests procedure is based on DGMK 377-01. In both scuffing tests with the sample the failure load stage = 8 was achieved. For case-carburized gears a medium to high amount of wear can be detected. Additional tests with ... Read More

Source

Water-lubricated bearings are widely used in propulsion shafting of large marine equipment, such as ships. When a water-lubricated stern bearing operates in harsh environments involving a low speed and heavy load for extended periods, there is a serious impact on the friction and wear performance of the bearing. In this study, a full pair of bearings made of a special polymer material was used as the research object in a sediment environment and was subjected to low-speed heavy-duty durability tests. At different temperatures, specific pressures, and speed conditions, the friction coefficient and wear were measured and linearly extrapolated. The results show that under harsh working conditions such as low speed and heavy load sediment, and the loading pressure is greater. It is difficult to form a complete water film between the friction pairs. A loading pressure of 0.2 MPa is beneficial to the long-term operation of the bearing under harsh working conditions. Moreover, the bearing damage is not serious, resulting in a reduction in bearing wear and an extension of operation life.

Source