Tribological Testing of Hemispherical Titanium Pin Lubricated by Novel Palm Oil:Evaluating Anti-Wear and Anti-Friction Properties

In this study, the properties of hip implant material and lubricants were examined using a pin on disc apparatus, to compare the effect of metal-on-metal （MoM） contact with a bio-lubricant derived from palm oil. The behaviour of the lubricants was observed during the experiments, in which a hemispherical pin was loaded against a rotating disc with a groove. A titanium alloy was used to modify the hemispherical pin and disc. Before and after the experiments, the weight and surface roughness were analysed, to detect any degradation. The results were compared according to the different kinematic viscosities. The wear rates and level of friction with each lubricant were also examined. The lubricant with the highest vis- cosity had the lowest frictional value. Therefore, develop- ing suitable lubricants has the potential to prolong the lifespan of prostheses or implants used in biomedical applications. The experiments collectively show that lubricants derived from palm oil could be used as efficient bio-lubricants in the future.

Surface Modified TiO2 Nanoparticles-an Effective Anti-wear and Anti-friction Additive for Lubricating Grease

The surface modified TiO_2 nanoparticles were prepared by using 12-hydroxystearic acid chemically modified on the TiO_2 surface. The average size of the TiO_2 particles is about 30 nm. The optimum ratio of tetrabutyl titanate to 12-hydroxystearic acid was 1/0.5. The bonding form between 12-hydroxystearic acid and TiO_2 nucleus was investigated by FTIR, DSC, TGA and XRD techniques. The lubricating grease containing the surface modified TiO_2 nanoparticles possesses excellent anti-wear and anti-friction properties. Compared with the grease without TiO_2, the PB value can be increased by 52% as the best performance of the grease containing surface modified TiO_2 nanoparticles, while the friction coefficient can be reduced by 33% with the addition of a small amount of TiO_2 nanoparticles, and meanwhile the wear scar diameter decreases by 25%.

Enhancing the Tribological Performance of Conductive Grease Through the Modification of Polypyrrole with Ionic Liquids

This study prepared four types of ionic liquid-modified polypyrrole(IL-modified PPy)as conductive additives and investigated their tribological performance and conductivity in polytetrafluoroethylene lubricating grease.The results indicated that IL-modified PPy effectively enhanced the anti-wear performance and conductivity of the base grease.Among the additives,1-octyl-3-methylimidazolium tetrafluoroborate([OMIm][BF4])modified PPy showed superior performance compared to the other three additives,with the best effect observed at a mass fraction of 0.5%.X-ray photoelectron spectroscopy analysis revealed that IL-modified PPy forms a stable friction chemical film during the friction process,effectively enhancing the lubrication performance and conductivity of the base grease.This indicates broad potential applications in the field of conductive lubrication.

Recent advances in friction and lubrication of graphene and other 2D materials:Mechanisms and applications

Two-dimensional materials having a layered structure comprise a monolayer or multilayers of atomic thickness and ultra-low shear strength.Their high specific surface area,in-plane strength,weak layer-layer interaction,and surface chemical stability result in remarkably low friction and wear-resisting properties.Thus,2D materials have attracted considerable attention.In recent years,great advances have been made in the scientific research and industrial applications of anti-friction,anti-wear,and lubrication of 2D materials.In this article,the basic nanoscale friction mechanisms of 2D materials including interfacial friction and surface friction mechanisms are summarized.This paper also includes a review of reports on lubrication mechanisms based on the film-formation,self-healing,and ball bearing mechanisms and applications based on lubricant additives,nanoscale lubricating films,and space lubrication materials of 2D materials in detail.Finally,the challenges and potential applications of 2D materials in the field of lubrication were also presented.

Preparation and Tribological Properties of Lanthanum-doped Muscovite Composite Particles as Lubricant Additives in Lithium Grease

Lanthanum-doped muscovite(MC) composite particles(hereinafter abbreviated as La-MC) were prepared by the mechanical solid-state-chemistry-reaction method, followed by surface modification with oleic acid. The microstructure of materials was characterized by SEM, XRD, EDS and FTIR. Furthermore, the friction-reduction and anti-wear properties of MC and La-MC as lubricant additives in lithium grease were evaluated using a four-ball friction and wear tester. The results showed that La(OH)_3 nanoparticles were coated on the surface of muscovite. Both MC and La-MC can effectively improve the friction-reduction and anti-wear properties of lithium grease and La-MC presents better tribological properties than MC. The excellent tribological properties of La-MC can be attributed to the formation of the adsorbed La-MC film and the chemical reaction film mainly composed of Fe_2O_3 and SiO_2 on the worn surface, as well as the catalysis of lanthanum element during the friction process.

Metal matrix nanocomposites in tribology: Manufacturing, performance, and mechanisms

Metal matrix nanocomposites(MMNCs)become irreplaceable in tribology industries,due to their supreme mechanical properties and satisfactory tribological behavior.However,due to the dual complexity of MMNC systems and tribological process,the anti-friction and anti-wear mechanisms are unclear,and the subsequent tribological performance prediction and design of MMNCs are not easily possible:A critical up-to-date review is needed for MMNCs in tribology.This review systematically summarized the fabrication,manufacturing,and processing techniques for high-quality MMNC bulk and surface coating materials in tribology.Then,important factors determining the tribological performance(mainly anti-friction evaluation by the coefficient of friction(CoF)and anti-wear assessment with wear rate)in MMNCs have been investigated thoroughly,and the correlations have been analyzed to reveal their potential coupling/synergetic roles of tuning tribological behavior of MMNCs.Most importantly,this review combined the classical metal/alloy friction and wear theories and adapted them to give a(semi-)quantitative description of the detailed mechanisms of improved anti-friction and anti-wear performance in MMNCs.To guarantee the universal applications of these mechanisms,their links with the analyzed influencing factors(e.g.,loading forces)and characteristic features like tribo-film have been clarified.This approach forms a solid basis for understanding,predicting,and engineering MMNCs’tribological behavior,instead of pure phenomenology and experimental observation.Later,the pathway to achieve a broader application for MMNCs in tribo-related fields like smart materials,biomedical devices,energy storage,and electronics has been concisely discussed,with the focus on the potential development of modeling,experimental,and theoretical techniques in MMNCs’tribological processes.In general,this review tries to elucidate the complex tribo-performances of MMNCs in a fundamentally universal yet straightforward way,and the discussion and summary in this review for the tribological performance in MMNCs could become a useful supplementary to and an insightful guidance for the current MMNC tribology study,research,and engineering innovations.

Physicochemical and Tribological Properties of Anti-Seize Thread Lubricant

The di-aromatics base oil and graphite powder,blended with the viscosity index improver,and the anti-oxidant and rheological additive,were used to prepare a kind of anti-seize thread lubricant.Its physical chemistry properties,such as water resistance,thermal oxidation and aging properties,and tribological performance,were evaluated and compared with those of some commercial products.The results show that the overall performance of the anti-seize thread lubricant could meet the level of some commercial products,while its some properties such as thermal stability,anti-wear and anti-friction properties were better.The said anti-seize thread lubricant is more suitable for use under high temperature conditions.

Study on Tribology Performance of Different Lubricant Additives under Atmospheric Pressure and High Vacuum Conditions

By using PAO-10 as the base oil, the tribological behavior of 11 additives under high vacuum condition was evaluated. By adopting some surface analytical instruments, such as scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS), the tribological mechanisms of these additives were studied. In air, O_2 can react with metal to form metal oxide that can protect the surfaces of rubbing pair during the tribological tests. According to the theory of the competitive adsorption, the function of some active elements is weakened. In a vacuum environment, the additives contributed more to the lubrication performance. The sulfur-containing additives could react with Fe to produce Fe Sx and "M—C" bonds("M" represents metal). They both had contributions to the lubrication. As for the phosphorus-containing additives, they only generated the phosphates during the tests. When the sulfur and phosphorus-containing additives were applied, the generated phosphates and Fe Sx had the primary contribution to the lubrication performance during the tests.

Progress on Bionic Textured Cutting Tools:A Review and Prospects

Cutting tools are known as the“productivity”of the manufacturing industry,which affects the production efficiency and quality of the workpiece,and has become the focus of research and attention in academia and industry.However,traditional cutting tools often suffer from adhesion or wear during the cutting process,which considerably reduces the cutting efficiency and service life of the tools,and makes it difficult to meet current production requirements.To solve the above problems,scholars have introduced bionics into the tool’s design,applying the microscopic structure of the biological surface to the tool surface to alleviate the tool’s failure.This paper mainly summarizes the research progress of bionic textured cutting tools.Firstly,categorize whether the bionic texture design is inspired by a single organism or multiple organisms.Secondly,it is discussed that the non-smooth surface of the biological surface has five characteristics:hydrophilic lubricity,wear resistance,drag reduction and hydrophobicity,anti-adhesion,and arrangement,and the non-smooth structure of these different characteristics are applied to the surface of the tool is designed with bionic texture.Furtherly,the cutting performance of bionic textured cutting tools is discussed.The anti-friction and wear-resisting mechanism of bionic textured cutting tools is analyzed.Finally,some pending problems and perspectives have been proposed to provide new inspirations for the design of bionic textured cutting tools.

Effect of Counterparts and Applied Load on the Tribological Behavior of the Graphene–Nickel Matrix Self-Lubricating Composite

Graphene-oxide (GO) has been recognized as an excellent lubrication material owing to its two-dimensional structure and weak interlayer interactions. However, the functional groups of GO that can contribute to anti-friction, anti-wear, and superlubricity are yet to be elucidated. Hence, further improvement in GO-family materials in tribology and superlubricity fields is impeded. In this study, macroscale superlubricity with a coefficient of friction of less than 0.01 is achieved by exploiting the high adhesive force between amino groups within aminated GO (GO–NH_(2)) nanosheets and SiO_(2). It was observed that GO–NH_(2) nanosheets form a robust adsorption layer on the worn surfaces owing to the high adsorption of amino groups. This robust GO–NH_(2) adsorption layer not only protects the contact surfaces and contributes to low wear, but also causes the shearing plane to transform constantly from solid asperities (high friction) into GO–NH_(2) interlayers (weak interlayer interactions), resulting in superlubricity. A SiO_(2)-containing boundary layer formed by tribochemical reactions and a liquid film are conducive to low friction. Such macroscale liquid superlubricity provides further insights into the effect of functional groups within functionalized GO materials and a basis for designing functionalized GO materials with excellent tribological performances.

Oil-soluble ionic liquids as antiwear and extreme pressure additives in poly-α-olefin for steel/steel contacts

To enhance the lubricating and extreme pressure(EP) performance of base oils, two types of oil-soluble ionic liquids(ILs) with similar anion albeit dissimilar cations were synthesized. The physical properties of the prepared ILs were measured. The anticorrosion properties of ILs were assessed by conducting corrosion tests on steel discs and copper strips, which revealed the remarkable anticorrosion properties of the ILs in comparison with those of the commercial additive zinc dialkyldithiophosphate(ZDDP). The tribological properties of the two ILs as additives for poly-α-olefin-10(PAO10) with various mass concentrations were investigated. The tribological test results indicate that these ILs as additives are capable of reducing friction and wear of sliding contacts remarkably as well as enhance the EP performance of blank PAO10. Under similar test conditions, these IL additives exhibit higher lubricating and anti-wear(AW) performances than those of ZDDP based additive package in PAO10. Subsequently, X-ray photoelectron spectroscopy(XPS) and energy dispersive spectrometer(EDS) were conducted to study the lubricating mechanism of the two ILs. The results indicate that the formation of tribochemical film plays the most crucial role in enhancing the lubricating and AW behavior of the mixture lubricants.