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In the present paper, the influence of load and sliding speed on super-low friction of Nitinol 60 alloy was investigated experimentally using Nitinol 60 alloy pin sliding over GCr15 steel disk under castor oil lubrication. Super-low coefficient of friction (COF) of Nitinol 60 alloy was achieved at the stable state, corresponding to so-called superl...
Contexts in source publication
Context 1
... oil possesses different physical and chemical properties [14][15][16]. However, regardless of its country of origin or season in which it was grown, its chemical composition remains relatively constant, as shown in Table 2. Castor oil is a triglyceride composed of various fatty acids and glycerol. ...
Context 2
... low friction is obtained because it probably results from the lubrication effect of the formation of lubricating films on Nitinol 60 alloy pin and on GCr15 steel surface. The main component and structure of castor oil are hydroxyl oleic acid, as shown in Table 2 and Fig. 4. Castor oil has a special property that makes them particularly desirable over petroleum-based oils in lubrication application. This property is related to the fact that castor oil has three alkyl ester groups of long-chain fatty acids, which has an ability to form a thin film of intermolecular layer which promotes boundary lubrication hence helps to reduce friction between the interfaces. ...
Citations
... Nitinol 60/steel can achieve superlubricity by the lubrication of castor oil under boundary lubrication state. However, due to the poor oxidative stability of castor oil, superlubricity cannot be achieved at high speeds [30]. Ge et al. achieved superlubricity with both polar (polyalkylene glycols) and non-polar (PAO) oils between a steel/steel tribopair by pre-treating the interface with PEG(aq) [31]. ...
1-(4-ethylphenyl)-nonane-1,3-dione (0206) is an oil-soluble liquid molecule with rod-like structure. In this study, the chelate (0206-Fe) with octahedral structure was prepared by the reaction of ferric chloride and 1,3-diketone. The experimental results show that when using 0206 and a mixed solution containing 60% 0206-Fe and 40% 0206 (0206-Fe(60%)) as lubricants of the steel friction pairs, superlubricity can be achieved (0.007, 0.006). But their wear scar diameters (WSD) were very large (532 µm, 370 µm), which resulted in the pressure of only 44.3 and 61.8 MPa in the contact areas of the friction pairs. When 0206-Fe(60%) was mixed with PAO6, it was found that the friction coefficient (COF) decreased with increase of 0206-Fe(60%) in the solution. When the ratio of 0206-Fe(60%) to PAO6 was 8:2 (PAO6(20%)), it exhibited better comprehensive tribological properties (232.3 MPa). Subsequent studies have shown that reducing the viscosity of the base oil in the mixed solution helped to reduce COF and increased WSD. Considering the COF, contact pressure, and running-in time, it was found that the mixed lubricant (Oil3(20%)) prepared by the base oil with a viscosity of 19.7 mPa·s (Oil3) and 0206-Fe(60%) exhibited the best tribological properties (0.007, 161.4 MPa, 3,100 s).
... The formation of the slip layer depends on the nature of the liquid and the micro-nano structure of the solid surface. On the one hand, the lower the viscosity of the liquid, the easier the formation of the slip layer; on the other hand, the more complete the micro-nano structure of the solid surface, the better the stability of the slip layer [125][126][127]. ...
Friction and the wear caused by friction will not only lead to energy dissipation, but will also cause damage to the function of mechanical parts, affecting the precision and lifespan of mechanical devices. Superlubricity as an ideal state of zero friction has become a hot research topic in recent years. There have been many reviews on the concept, origin, and research progress of superlubricity, but, among them, there are more presentations on the research status of solid superlubricity and liquid superlubricity; however, the theoretical summarization of solid–liquid combined superlubricity and high-temperature superlubricity is still imperfect and lacks a systematic and comprehensive review. The mechanism of superlubricity is not explicitly presented in many reviews, which are clearly summarized in this paper. This paper introduces superlubricity from friction, and then introduces the origin of superlubricity, and presents the research progress on superlubricityby separating it into in four categories: liquid superlubricity, solid superlubricity, solid–liquid combined superlubricity, and high-temperature superlubricity. By analyzing the superlubricity system, the mechanism of realizing various types of superlubricity, such as incommensurability, hydration, and oxidation, is summarized. Based on the research progress of superlubricity, the development prospects, opportunities, and challenges of superlubricity in the future are discussed.
... A mesh texture was first prepared on the surface of high-speed steel, and then nylon fibers were implanted into the grooves of the texture as a solid lubricant by the electrostatic flocking technology. Zeng et al. 22 reported that the application of vegetable oil in machining has been increasing in recent years due to the emphasis on sustainable manufacturing. Among these, castor oil has excellent lubricating properties due to its higher viscosity. ...
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.
... With the rise in petroleum prices, there has been a considerable surge in demand for ecologically friendly oil-based surfactants derived from natural renewable resources. Monoricinolein (MRO) with at least three hydroxyl groups outperforms ordinary MAG in terms of emulsification and lubrication [3]. Besides, MRO can be used to prepare ferroelectric liquid crystals and film-forming agent [4,5]. ...
Monoricinolein (MRO) is a renewable and biodegradable surfactant derived from castor oil (CO). In this work, a novel ionic liquid (IL)-catalyzed method for selective MRO preparation by the glycerolysis of CO was investigated. Six basic ILs ([Bmim]Im, [Bmim]OH, [Bmim]DCN, [Bmim]OAc, [Emim]OAc, [Emim]Im) were screened and evaluated as homogeneous catalysts. Among the tested ILs, [Bmim]Im showed the best catalysis performance. An evaluation of the effects of reaction variables on the IL-catalyzed glycerolysis was carried out (temperature, reaction time, IL load and substrate ratio). The maximum MRO yield (75.77 ± 1.20%) and triacylglyceride (TAG) conversion (96.67 ± 0.10%) were obtained under the following optimized conditions: CO/glycerol molar ratio 1:6, IL load 10%, 180 °C, 3 h, and no water added. The results showed that the selectivity of MRO was enhanced. The activation energies (Ea) for CO conversion and formation of the MRO were 44.07 kJ/mol and 54.99 kJ/mol, respectively.
Graphical Abstract
... For castor oil, the fluctuation was around 3000, indicating that the C=C had changed, and the fluctuation around 1300-800 manifested that the ether (C-O), hydroxyl (C-OH), carbonyl (C=O), and acid C(O)OH had varied. It was demonstrated that castor oil experienced an oxidative hydrolysis reaction, which is the same as the tribochemical reaction of castor oil mentioned in the previous literature [47][48][49][50][51][52]. The hydrolysis of castor oil produces more polar molecules, which are more favorable for forming boundary films. ...
... For silicone and castor The tribofilm mechanism of (a) white oil, (b) silicone oil and castor oil, and (c) castor oil oil, it has been evaluated that the friction coefficient of castor oil was much lower than that of silicone oil, and the running-in period was also shorter. The superior lubricating performance of castor oil is due to the polar molecules of castor oil that can adhere to the friction surface to form an orderly and closely packed boundary adsorption film, reducing the severe interaction between asperity contacts [51,52]. In comparison, silicone oil is nonpolar and could hardly adhere to the contact surface, providing little protection to asperity contacts. ...
The synergistic effect of surface texturing and lubricants with various viscosity and polarity properties is an attractive and unexplored topic. In this study, surface texturing characterized by circular dimples has been manufactured on steel surfaces in advance, which can improve the lubrication of frictional units compared with the bare disc under different lubricants. Then, three lubricants, low-viscosity and nonpolar white oil, high-viscosity and nonpolar silicone oil, and highly viscous and polar castor oil, were used to evaluate the interaction between surface texture and the lubricating oil. The contact angles of each lubricant on the textured and bare surface were measured to investigate the lubricant intermolecular force and wettability. The oil film thickness simulation and tribological experiments were conducted. The tribological results indicate that lubricants with varied characteristics work differently due to their different properties on textured surfaces. Castor oil exhibits the best tribological properties of the three-oil used to supply the textured surfaces, which may attribute to its ability to generate a strong boundary adsorption films as well as a thickened interfacial layer, and it could reduce the intensity of asperity interaction.
... Zeng and Dong [172] investigated the influence of superlubricity between Nitinol 60 alloy/GCr15 steel tribo-pair lubricated with castor oil by varying speeds and loads. Results revealed that, at stable state, CoF varies from 0.006 to 0.002 with increasing loads while CoF varies from 0.004 to 0.03 with increasing speeds. ...
To mitigate and control friction and wear are the primary goals in tribology for a moving mechanical system. On achieving ultra-low friction and wear, energy efficiency, performance and service life of a mechanical system are greatly extended. Superlubricitive technology is one of the emerging research topics in the field of tribology, and is broadly classified into liquid superlubricity and solid superlubricity. As compared to liquid superlubricity, achieving solid superlubricity might be challenging at macroscopic level and under atmospheric condition as it requires unique atmospheres. In addition to that, researchers have found more potential in liquid superlubricitive technology for industrial applications. In this comprehensive study, a state-of-the-art review on various aspects of superlubricitive technology including recent progress in solid superlubricity to achieve ultra-low friction have been presented. Specific detailed discussion has been carried out on the recent advancements in liquid superlubricitive technology. This study also highlights the challenges associated with liquid superlubricitive technology and frames some suggestions for future investigations in liquid superlubricitive technology. It is hoped that this study will help in enhancing reader's knowledge on superlubricitive technology and will guide researchers in seeking future directions and gaps in this area as well.
... Due to its origination of electrostatic double-layer force or hydration lubrication, water-based superlubricity is normally available for very limited tribological interfaces, such as ceramic and glass [7][8][9]. In comparison, oil-based superlubricity has attracted more and more attention because of its wide applications in lubricating mechanical engineering materials (especially steel) [10][11][12][13][14]. ...
... In recent years, some studies show that the steel tribological interface is capable of achieving superlubricity under lubrication of specific oil without any additive. Zeng and Dong [13] reported the superlubricity behaviors of Nitinol 60 alloy/steel interface with the lubrication of castor oil. They indicated that the castor oil dissociated at the tribological area to form OH-terminated surfaces, and the boundary wear-protective films is conducive to reducing friction largely. ...
... They indicated that the castor oil dissociated at the tribological area to form OH-terminated surfaces, and the boundary wear-protective films is conducive to reducing friction largely. However, the unstable chemical properties of castor oil due to the poor oxidation resistance limits its further applications at high sliding speed [13]. Amann and Kailer [14] found that the lubrication of 1,3-diketone enables superlubricity at steel sliding interface even under relatively highspeed conditions. ...
Achievement of steady and reliable super-low friction at the steel/steel contact interface, one of the most tribological systems applied for mechanical moving parts, is of importance for prolonging machine lifetime and reducing energy consumption. Here we reported that the superlubricity performance of the steel/steel sliding interface lubricated with tiny amounts of diketone solution strongly depends on the oxygen content in surrounding environment. The increase of oxygen not only significantly shortens the initial running-in time but also further reduces the stable coefficient of friction in superlubricity stage due to the enhancement of tribochemical reactions. On the one hand, more severe oxidation wear occurring at higher oxygen content facilitates material removal of the contact interface, lowering the contact pressure and the corresponding initial friction. On the other hand, the growth of iron ions during the shear process in high oxygen environment promotes the formation of chelate which acted as an effective lubricated film chemisorbed at the steel/steel friction interface to further lower the interfacial friction. The results provide a new opportunity to further optimize the tribological performance of diketone superlubricity system, especially towards the lubrication of mechanical engineering materials.
... This metal oxide/hydroxide layer formation is driven by tribochemical reactions between metallic surfaces and castor oil degradation products [11]. However, superlubricity of this system vanishes when sliding speed exceeds 8 m/min [12]. ...
... Summarising, a higher CoF shows up when no OH group is present in lubricants like PAO4. This observation is consistent with the fact that OH groups benefits friction reduction as already reported elsewhere [12]. It is worthy to note that under the same conditions, a-C(30) shows a lower friction coefficient than ta-C(55) while sliding in ricinoleic acid ( Fig. 4(b)). ...
... Their advantage derives from two aspects: firstly, OH function serves as anchoring spot to bridge oil molecule and surfaces [20]; secondly, the OH function helps for surface hydroxylation. DLC surfaces passivated by OH functions have been always associated with low friction in previous works [41,12]. However, in our case, CH x -termination (by both alkanes and alkenes) is the dominant mechanism because the characteristic CH 2 feature at 261.5 eV in the Auger CKLL peak is more intense when friction is low and this independently of the oxygen content of the lubricant (see the case of GMO for example in Fig. S2 in the ESM). ...
To meet the surging needs in energy efficiency and eco-friendly lubricants, a novel superlubricious technology using a vegetable oil and ceramic materials is proposed. By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp ² and sp ³ hybridized carbon in presence of a commercially available silicon nitride bulk ceramic, castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most. Besides a partial liquid film possibly separating surfaces in contact, local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds. High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities, thus helping both the chemical polishing of surface and its chemical passivation by H and OH species. Particularly, the formation of the formation of −(CH 2 −CH 2 ) n − noligomers have been evidenced to have a major role in the friction reduction. Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp ² -hybridized carbon atoms in the amorphous carbon structure. Hence, tuning sp ² -carbon content in hydrogen-free amorphous carbon, in particular, on the top layers of the coating, provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.
... This characteristic enables the material to resist denting damage [9,10] , while achieving comparable rolling/sliding per-formance to tool steels [3][4][5] . Furthermore, NiTi alloys can be lubricated, unlike Ti alloys, and have an even lower friction coefficient than tool steels under some oil lubrication conditions [4,11,12] . Nirich NiTi alloys and their unique set of properties are an enabling breakthrough for specialty bearing applications, especially for use in corrosive environments or where denting-damage resistance is critical. ...
The deformation mechanisms that dictate the tribological performances of heat treated Ni55Ti45, Ni54Ti45Hf1 and Ni56Ti36Hf8 alloys are revealed through rolling contact fatigue (RCF) testing and transmission electron microscopy (TEM) analyses. Analysis of worn samples that passed a 5×10⁸ cycle RCF runout condition shows that damage is primarily confined to deformation bands that propagate several hundred nanometers – to – several microns beneath the surface. These bands nucleate via localization of dislocation slip within the B2 austenite phase of the alloys. For the Ni55Ti45 and Ni54Ti45Hf1 samples, further damage and eventual spall failures occur by shearing and dissolution of the strengthening Ni4Ti3 nanoprecipitates within the deformation bands, followed by nanocrystallization that sometimes includes stress-induced nucleation of B19′ nanocrystals. Eventually, complete amorphization occurs prior to fracture. The relative 15 – 25% increase in RCF contact stress performance of the Ni56Ti36Hf8 alloy correlates with a more limited depth of damaged material beneath the wear surface; heavily damaged material beneath spall failure sites only extends 1.5 µm into the sample, compared to > 6 µm for Ni55Ti45 and Ni54Ti45Hf1 alloys. This superior RCF damage resistance of the Ni56Ti36Hf8 alloy results from a lower fraction of B2 matrix phase (≤ 13 %) that is highly confined by both cubic Ni-rich NiTiHf and H-phase nanoprecipitates. Specifically, this microstructure limits the widths of deformation bands within the B2 austenite phase to less than the size of the strengthening nanoprecipitates, which in turn inhibits precipitate shearing and dissolution processes that precede nanocrystallization and amorphization.
... The author's previous research studies showed that the coefficient of friction (CoF) becomes high with increasing speed due to friction heating under castor oil lubrication. 24,25 It is inferred that the viscosity of castor oil may play a significant role in the lubrication performance of castor oil. It is well known that the temperature affects the viscosity of oil during sliding. ...
... The fatty acids of castor oil are constituted by ricinoleic acid, oleic acid, stearic acid, palmitic acid, linolenic acid and other acids, as shown in Table 3. 25 To verify the microstructure of castor oil after the tribotest, FTIR spectroscopy is carried out. Figure 1 shows the FTIR spectrum of castor oil after the tribotest at 40°C. ...
... The tribological properties of castor oil are compared with those of a mineral-based lubricant and other lubricants. [23][24][25] Although the well-known challenge of castor oil as a lubricant is its low stability, castor oil exhibits super-low friction compared with other lubricants for the friction pair of steel ball/NiTi alloy disk. Figure 2 shows the variation in the CoFs of castor oil with respect to the sliding time under various temperatures. ...
Castor oil is an environment-friendly lubricant with good biodegradability and renewable behavior. However, castor oil as a green lubricant has a few shortcomings, such as a low viscosity index and low oxidative stability due to the presence of unsaturated bonds. The temperature affects the lubrication performance of castor oil. In the present study, the lubrication performance and viscosity behavior of castor oil lubricating the friction pair of a steel ball and a nickel–titanium (NiTi) alloy disk were systematically investigated under different temperatures. The results show that the lubrication performance of castor oil is influenced by temperature due to the fact that the viscosity of castor oil varies with the temperature. The coefficient of friction (CoF) of castor oil is as super-low as 0.076 at a temperature of 40°C, but is relatively high at other temperatures. The factors affecting the lubrication performance were investigated, and a possible antifriction mechanism is proposed in this study.
