Lubrication oils tribological properties

Abstract This chapter reviews state-of-the-art research on ionic liquids (n.s) as lubricants. The discovery of ILs as high-performance synthetic lubricants in 2001 immediately attracted considerable attention in the field of tribology. Such lubricants have better lubrication performance and antiwear capabilities than conventional lubrication oils. This chapter first introduces a brief summary of tribology and ILs. It then details the tribological research status of ILs, including their tribological properties and functionalization. Finally, trends in future ILs research are presented. 

ILs have attracted considerable attention in the field of tribology because of their remarkable lubrication and antiwear capabilities compared to lubrication oils, fit recent years, ILs have been applied and yielded excellent performance compared to traditional lubricants, but they have a number of problems, such as corrosion, oxidation instability, and very poor miscibility with base oil. These factors limit their industrial applications as lubricants [2]. Fortunately, these problems are not very difficult to address, as ILs have structures that may easily be modified. Conferring ILs with special functions, such as antioxidation and anticorrosion properties and enhanced capability for specific substrates, may be easily performed by synthetic chemists. It is hoped that future work on ILs will produce multifunctional lubricants with oxidation and corrosion resistance that may be applied in the industrial scale [2, 100]. 

Despite the large number of liquid crystals reported in the literature, only a few classical TLCs and even fewer LLCs have been investigated for their tribological properties (1-8L A number of investigators have reported reduced coefficients of friction, reduced wear, reduced temperature in the contact zone and increased load-bearing properties between various surfaces when TLCs were used as lubricants by themselves or added to base oils. However, almost all of these studies were conducted under hydrodynamic conditions. Thus, we decided to... 

Surfactants play an important role in tribology. The role of surfactants in tribology is related to the amphiphilic (dual) nature of surfactant molecules, which is both hydrophilic and hydrophobic. The amphiphilic nature of surfactaut molecules leads to aggregation and adsorption, which are important to tribology. Surfactants have the ability to adsorb on metal surfaces to produce hydrophobic surfaces that are more receptive to lubricating oils than unaltered metal surfaces, which are naturally hydrophilic. Surfactauts can also impart lubrication properties in the absence of oil. Thus, surfactant molecules play an important role in common tribological applications involving a variety of surfaces and lubricants. 

The effects of additive concentration, compound structure and friction pair material on tribological properties were discussed on the basis of the results obtained. A comparison of the simple binary systems with commercial lubricant compositions based on mineral oils was made. The result of the comparison indicates that aqueous solutions may be applied in real tribological systems. 

Cizaire et al. sffidied IF-M0S2 as lubrication additives in boundary lubrication [29]. Added at 1 wt % to a poly-alpha-olefin (PAO) synthetic base oil, IF-M0S2 led to a very low friction coefficient of about 0.06. Nevertheless, no clear lubrication mechanism was proposed. In this section, works related to the study of the effect of the concentration and pressure on the tribological properties of IF-M0S2 are reported. Tests were carried out on the environmental pin-on-fiat tribometer (described in the Appendix in Section A.l). 

In the boundary lubrication regime, the antiwear and Mction-reduction processes are associated to the build-up of a tribologic film resulting from the chemical reaction between oil additives and sliding surfaces in contact [1-3]. The case of zinc dialkyl dithiophosphate (ZDDP) additive has been extensively studied by analytical transmission electron microscopy (ATEM) and the morphology, nature, structure and tribologic properties of the tribochemical film were obtained [4-6], The Figures 4.1 and 4.2 summarize the main results. 

Soft metals such as indium, tin and bismuth are good solid lubricants, but they cannot be used as a lubricating oil additive because of their poor dispersibility in oils. However, their nanoparticles prepared by the direct solution-dispersing method have been found to have better oil solubility and can be directly used as lubricating additives. Their tribological properties have been evaluated on a four-ball tester and the results are presented as follows. 

In practice, low melting point metals are often used to prepare lubricating coatings in the form of metals alloys to achieve the most optimizing properties, and nanoparticles of alloyed metals are anticipated to have tunable excellent tribological properties as the composition of the alloys is varied. Until today, nanoparticles of In-Sn, Bi-In, Pb-Bi, Sn-Bi and Sn-Cd alloys that can be dispersed in oils have been synthesized and their tribological properties have been studied. 

This study has focused on material couples as shown in Table 1. Tribological properties of these materials in lubricating oils were examined using a reciprocating pin-on-plate system. The pin was loaded using a static load applied through a lever... 

Rani, S., Joy, M.L., Nair, K.P., 2015. Evaluation of physiochemical and tribological properties of rice bran oil — biodegradable and potential base stoke for industrial lubricants. Industrial Crops and Products 65, 328—333. Available at http //www.sciencedirect.coni/science/ article/pii/S0926669014007857 (accessed 21.04.15.). 

The HH, HL, HM, HR, HV and HG hydraulic lubricants are the most important and widely used. As viscosity is one of their most important properties, they are produced in a wide range of viscosities, ISO VG 10-100. For a given application, viscosity should be as low as possible to give a rapid response for the hydraulic system, meaning that the oil should be sufficiently fluid for efficient power transmission. A minimum viscosity level is necessary to eliminate or minimize leakage losses and ensure lubrication of all tribological elements of the hydraulic system. 

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