Due to the increasing demand of low emission and fuel economy, friction modifiers have been widely used in lubricating compositions to adjust friction and wear properties of lubricants. Recent achievements in the application of friction modifiers for liquid lubricants (2007–present) are reviewed in this paper. There are three types of friction modifiers for liquid lubricants: organomolybdenum compounds, organic friction modifiers, as well as nanoparticles. The tribological properties and lubrication mechanisms of these friction modifiers are discussed. The problems and some suggestions for the future directions of research on friction modifiers are proposed.

A review of recent developments of friction modifiers for liquid lubricants (2007–present)

Modern engine lubricant specifications include compositional constraints in terms of the permitted level of sulphated ash, phosphorus and sulphur (SAPS). This necessitates a reduction in the concentration of the additive zinc dialkyldithiophosphate (ZDDP) used in engine oils, and there is currently great interest in identifying anti-wear additives that contain low or zero SAPS to partially or wholly replace ZDDP.

This paper reviews the main chemical classes that are reported in the literature as potential low- or zero-SAPS anti-wear agents. There are many such possible additives, although none appears to be quite as versatile as ZDDP. Instead, combinations of anti-wear and extreme pressure additives are likely to be employed in the future. The literature reveals a strong imbalance in the amount and depth of research carried out on the various additive types, with a great deal of research on a few classes of additives and very little recent work on most others. Copyright © 2007 John Wiley & Sons, Ltd.

Low- and zero-sulphated ash, phosphorus and sulphur anti-wear additives for engine oils

http://www.ysxbcn.com/down/upfile/soft/2008617/2008617165616790.pdf

Tribological properties and lubricating mechanisms of Cu nanoparticles in lubricant

Abstract The friction between two sliding surfaces is probably one of the oldest problems in mechanics. Frictional losses in any I.C. engine vary between 17% and 19% of the total indicated horse power. The performance of internal combustion engines in terms of frictional power loss, fuel consumption, oil consumption, and harmful exhaust emissions is closely related to the friction force and wear between moving parts of the engine such as piston assembly, valve train, and bearings. To solve this problem, most modern research in the area of Nanotribology (Nanolubricants) aims to improve surface properties, reduce frictional power losses, increase engine efficiency, and reduce consumed fuel and cost of maintenance. Nanolubricants contain different nanoparticles such as Cu, CuO, TiO2, Ag, Al2O3, diamond, and graphene oxide. This paper demonstrates the effect of nanoparticles on the tribological behavior of the engine oil. The main objective of this review is to present recent progress and, consequently, develop an exhaustive understanding about the tribological behavior of engine oils mixed with nanoparticles.

https://www.degruyter.com/downloadpdf/j/ntrev.2015.4.issue-4/ntrev-2015-0031/ntrev-2015-0031.xml

Improving the tribological behavior of internal combustion engines via the addition of nanoparticles to engine oils

Thermal spraying of transition metal aluminides: An overview

Sliding wear behavior of Fe–Al and Fe–Al/WC coatings prepared by high velocity arc spraying

The tribological behaviors of the nano-diamond particles including the nano-diamond and the nano-diamond modified were studied at high temperature using SRV multifunctional test system. The worn steel surfaces were analyzed by means of X-ray photoelectron spectroscopy (XPS). The results show that nano-diamond particles can obviously improve the antiwear and friction reducing properties of the base oil at high temperature and the high load. The friction coefficient of the nano-diamond is very low at 200 °C when the test load is not more than 20 N. This tribological behaviors should attributed to the similarly to “ball bearing” lubrication action of the nano-diamond particles, so the movement between tribological pairs become sliding/rolling. The nano-diamond modified by dimer ester possesses excellent antiwear and friction reducing performance at 500 °C and load 500 N. The tribochemical reaction film between the nano-diamond particles and the renascent wear surface plays dominating lubrication role and the presence of the dimer ester on the rubbing surface can be propitious to form lubrication film containing nano-diamond on the worn surface at high temperature and high load.

High temperature tribological behaviors of nano-diamond as oil additive

The tribochemical mechanism of the borate modified by N-containing compound as oil additive

An N-modified nano / micrometre borate (MNMB) as an oil additive was synthesised by an ultrasonic dispersion and emulsion reaction in the microemulsion phase. The particles of the MNMB additive were between 20 and 500 nm in diameter. The tribological properties of the MNMB as an oil additive were investigated using a four-ball tester. The results reveal that the MNMB possesses good tribological properties. When the boron concentration is 0. 05 wt. %, the wear-scar diameter is smallest and the seizure load is highest. The antiwear and extreme-pressure properties of the MNMB were best at a viscosity of 65. 3 mms2. Small-area X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA) indicate that the MNMB additive can form a tribological mixed reaction film containing C, O, B, N, and Na on a rubbing surface. The elemental boron exists in four different chemical states, but is mainly present in the form of BN on the rubbing surface.

The tribochemical performance of nano/micrometre borate modified by an N‐containing compound as an oil additive

Fe-Al intermetallics with remarkable high-temperature intensity and excellent erosion, high-temperature oxidation and sulfuration resistance are potential low cost high-temperature structural materials. But the room temperature brittleness induces shape difficult and limits its industrial application. The Fe-Al intermetallic coatings were prepared by high velocity arc spraying technology with cored wire on 20G steel, which will not only obviate the problems faced in fabrication of these alloys into useful shapes, but also allow the effective use of their outstanding high-temperature performance. The Fe-Al/WC intermetallic composite coatings were prepared by high velocity arc spraying technology on 20G steel and the oxidation performance of Fe-Al/WC composite coatings was studied by means of thermogrativmetic analyzer at 450, 650 and 800°C. The results demonstrate that the kinetics curve of oxidation at three temperatures approximately follows the logarithmic law. The composition of the oxidized coating is mainly composed of Al2O3, Fe2O3, Fe3O4 and FeO. These phases distribute unevenly. The protective Al2O3 film firstly forms and preserves the coatings from further oxidation.

Binshi Xu

Papers

Sliding wear behavior of Fe–Al and Fe–Al/WC coatings prepared by high velocity arc spraying

High temperature tribological behaviors of nano-diamond as oil additive

The tribochemical mechanism of the borate modified by N-containing compound as oil additive

The tribochemical performance of nano/micrometre borate modified by an N‐containing compound as an oil additive

Oxidation performance of Fe-Al/WC composite coatings produced by high velocity arc spraying