Study on the Tribological Properties of F-T DS/ZnFe-LDH Composite Lubricating Material

The homemade soot capture device was used to burn Fischer-Tropsch synthetic diesel (F-T diesel) in order to simulate the combustion of F-T diesel in the engine and collect its soot (F-T DS, FS). The zinc-iron hydrotalcite (ZnFe-LDH) and the composite materials of FS and ZnFe-LDH (F-T DS/ZnFe-LDH, FS/ZnFe-LDH) were prepared by hydrothermal synthesis, and the similarities and differences in tribological characteristics of the above three lubricating materials such as 10# white oil (10# WO) lubricant additives were investigated. FS is an aggregation composed of amorphous carbon and graphite microcrystals. ZnFe-LDH is mainly composed of nanosheets, Zn, and Fe hydroxide particles, with a high degree of crystallization, while FS/ZnFe-LDH is a “sandwich layer” composed of nanosheets and soot particles. Because of the addition of cetyltrimethylammonium bromide and the grafting of a long carbon chain lipophilic group in the preparation process, FS/ZnFe-LDH has better anti-wear properties than the FS and ZnFe-LDH Effect. When FS/ZnFe-LDH is added at 0.2 wt.%, the average friction coefficient (AFC) and average wears scar diameter (AWSD) are at their lowest. Compared with pure 10# WO, the minimum values of AFC and AWSD have dropped by 36.84% and 22.58%, respectively. XPS analysis of the wear scar surface shows that when ZnFe-LDH and FS/ZnFe-LDH are used as lubricating additives of 10# WO, together with the organic matter in the white oil and the iron element in the friction pair, tribochemistry occurs under the combined action of the adsorption force and the tribochemical reaction, a friction protection film containing four elements of C, O, Fe, and Zn is formed on the surface of the wear scar, which effectively reduces the wear and reduces the friction coefficient.

3D texture parameters for wear scars after severe regime

Purpose This paper aims to present an analysis of several 3 D texture parameters for the entire wear scars obtained in severe regime, on a four-ball tester. The aim of this analysis is to correlate the tribological parameter as wear scar diameter to texture parameters. Design/methodology/approach Tested lubricants were rapeseed oil, rapeseed oil additivated with 1% Wt nano TiO2 and rapeseed oil additivated with 1%Wt nano ZnO. The severe regime was applied for 1400 rpm and for loads increasing in steps of 50 N, from 500 to 900 N. Several analyzed roughness parameters (height parameters and functional ones) could be related to the evolution of a wear parameter, the wear scar diameter. Comparing the values for neat rapeseed oil and additivated variants, the texture parameters allow for evaluating if the additives protect or not the worn surfaces. Findings Measurements pointed out two groups of roughness parameters: one that has an evolution depending on wear scar diameter (WSD) and load (Sa, St, functional parameters) and one including Ssk that has shown no dependence on load and WSD. Also, the functional parameters Spk and Svk follow in a similar manner the wear parameter, WSD, but Sk is the least dependent on load. For the highest load, amplitude parameters such as Sa and St are following the tendency of WSD. Each lubricant has its particular correlation between wear parameters and texture quality, expressed by the help of a set of roughness parameters. Research limitations/implications Such studies help tribologists to rank lubricants based on a combined analysis with wear parameters and texture parameters. Practical implications The results allow for evaluating new formulated lubricants. Originality/value The study on the quality on worn surfaces introduces the original idea of analyzing the entire wear scar surface (approximated by an ellipse with the axes as those experimentally measured) by the help of a set of 3 D roughness parameters.

Дослідження змащувальної здатності дизельного та авіаційного палива на паливному насосі високого тиску

This paper presents comparative experimental study’s results of diesel fuel and aviation fuel effect on operational properties of a high-pressure fuel pump of a common rail injection system. The two identical fuel injection systems mounted on a test bed of the fuel injection pumps were prepared for the experimental durability tests. The lubricity properties of diesel fuel and aviation fuel (Jet-A1) were studied using the High-Frequency Reciprocating Rig (HFRR) method. The values of wear scar diameter (WSD) obtained with Jet-A1 fuels were compared to the respective values measured with the reference diesel fuel. The microscopic photographs of the wear scar diameters obtained on above mentioned fuels are presented in the paper. The test results showed that long-term (about 300 hours) using aviation fuels produced a negative effect on the durability of the high-pressure fuel pump. Due to the wear of plunger-barrel units the decrease in the fuel delivery rate occurred of about 6.7 % operating with aviation fuel. The average friction coefficients of Jet-A1 fuels were higher than that of the normal diesel fuel. Keywords: diesel fuel, aviation Jet-A1 fuel, lubricity, plunger-barrel units, wear scar diameter

Frictional Performance of an Ionic Liquid/Graphene Composite Additive in Lubricating Oil

In this study, we used a four-ball friction and wear testing machine to test the tribological properties of [HPy]BF4 ionic liquids (ILs), low-layer graphene (G), and IL and G compounds (IL/G) as lubricant additives at variousconcentrations, loads, and speeds. The morphology of the wear scar was characterized by a white-light interferometer and a scanning electron microscope (SEM). The results showed that the optimal concentrations of IL and G were 0.10[Formula: see text]wt.% and 0.05[Formula: see text]wt.%, respectively. When the IL concentration was 0.10[Formula: see text]wt.%, the friction coefficient and the wear scar diameter (WSD) reduced by approximately 18% and 8%, respectively, compared to the base oil. When the concentration of G was 0.05[Formula: see text]wt.%, the friction coefficient and WSD reduced by approximately 23% and 12%, respectively, compared to the base oil. After adding the optimal concentration of the IL/G composite additive under the same test conditions, the average friction coefficient of the steel ball reduced by approximately 30%, and the average WSD reduced by approximately 18%. IL/G nanoadditives could be easily attached to the pit area on the friction surface of the steel ball, which made the contact surface of the friction pair smoother and the area of the oil film bearing the load larger, compared to those using the base oil. These two combined phenomena promoted synergistic antifriction and antiwear effects, which significantly improved the frictional performance of the base oil.

Molecular Dynamics Study on Nano-Friction and Wear Mechanism of Nickel-Based Polycrystalline Superalloy Coating

In this work, molecular dynamics simulations are employed to study the nanotribological process of nickel-based polycrystalline superalloy coating. A series of simulations were carried out using the method of repeated friction to explore the influence of frictional force, friction coefficient, grinding groove morphology, wear scar depth, debris flow direction, subsurface damage degree and evolution of defects during the nano-friction process. In addition, the change mechanism of different grain sizes on wear scar depth, frictional force, friction coefficient, and internal damage in the repeated friction process is also explored. The results show that the frictional force is related to the direction of the dislocation slip, and that the friction coefficient change is related to the number of repeated frictions. Moreover, it is observed that the grinding ball has a shunting effect on the formed wear debris atoms, and the shunt point is located at the maximum horizontal radius. We reveal that the grain boundary structure has a strengthening effect. When the grinding ball rubs to the grain boundary, the nucleation of dislocation defects inside the workpiece is obviously hindered by it. Simultaneously, we also find that the closer the subsurface is to the bottom of the grinding ball, the greater the degree of damage to the workpiece by friction. Furthermore, with the grain size decreases that the material begins to soften, resulting in a decrease of frictional force, friction coefficient, and smaller defects are formed inside the workpiece. The research of this work can better clarify the microscopic mechanism of the polycrystalline friction process.

Research on the Elastic Properties of Discontinuous Contact Wire Rope for WR-CVT

This study mainly conducts the research on the discontinuous contact elastic properties of wire rope based on WR-CVT. The geometry model and finite element model of continuous contact and discontinuous contact of 2/3 lay pitch wire rope are established. And the contact stress distribution of the steel wire is analyzed through 5 sections and 5 contact points. The results show that on the C-C plane, the contact stress of the discontinuous contact model is 229.4 MPa higher than that of the continuous contact, but this difference is not obvious on the D-D plane. The contact stress nephogram is elliptical, but in the noncontact area, the shape of the contact trace shows a distinct noncomplete ellipse, and the contact trace is distributed along the spiral trajectory of the steel wire. Point 4 due to the reduction in contact area, compared with continuous contact, discontinuous contact shows a higher stress value. The geometric dimensions of the wear scars of continuous contact and discontinuous contact indicate that regardless of the length of the wear scar or the width of the wear scar, the geometric characteristics of steel wire wear mark in discontinuous contact are larger than that in continuous contact, so the discontinuous contact aggravates the surface wear of wire. This research lays a theoretical foundation for the discontinuous contact wear and fatigue of WR-CVT wire rope and other components.

Ultra-low wear and anti-oxidation properties of microcrystalline graphite oxide-magnesium silicate hydroxide composite nanoadditives in the poly-alpha-olefin base oil

Graphite-based materials and hydrothermal synthetic magnesium silicate hydroxide (MSH) had shown outstanding performances as lubricant additives. In this paper, microcrystalline graphite oxide-magnesium silicate hydroxide (MGO-MSH) composite additives using pre-oxidized MGO as one of the precursors were prepared at a mild hydration condition, and their tribological properties in poly-alpha-olefin oil (PAO 10) were demonstrated by a four-ball tester. The tribological results showed that the optimal concentration of MGO-MSH in oil was 0.3 wt% under 600 N, 600 rpm. Meanwhile, the average wear scar diameter of the ball samples tested in composite-suspending oil was reduced by 36.3% compared with that obtained by pure PAO 10. By means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectra, and X-ray photoelectron spectroscopy (XPS), it was verified that MGO was involved in the synthesis of MSH, and MSH was anchored on MGO during the hydrothermal process. In addition, it was confirmed that carbon-containing tribo-film was formed on the smooth wear region of the wear scar, and was of excellent anti-oxidation wear properties.

Tribological Behaviour and Lubricating Mechanism of Tire Pyrolysis Oil

The four-ball tester was used in this analysis to demonstrate the lubricity of tire pyrolysis oil (TPO). The tribological performance of the tire pyrolysis oil was compared with diesel fuel (DF) and their blends, DT10 (TPO 10%, Diesel 90%) and DT20 (TPO 20%, Diesel 80%). A scanning electron microscope (SEM) was used to investigate the wear scar. In contrast to diesel fuel, TPO demonstrated better antiwear behaviour in terms of higher load-carrying capacity. DT10, DT20, and TPO’s wear scar diameter (WSD) was 22.35%, 16.01%, and 31.99% smaller than that of diesel at 80 kg load, respectively. The scanning electron microscope micrographs showed that the TPO and DT10 had less wear than their counterparts.

A novel wear angle determination algorithm for wear image based on direction correlation of wear scar

A lubricant is a substance that lessens friction and wear between mechanical parts. A good quality lubricating oil is required for protecting the mechanical equipment and reducing energy consumption. Its performance index (friction coefficient) could be measured by the four-ball wear test. For the morphological analysis of testing data from the four-ball wear test, determination of wear angle is very important for measuring the wear spot diameter, validity of the four-ball wear test and recognition of abnormal wear scar. On the basis of character analysis and image processing technology, a novel wear angle determination algorithm for wear scar is presented in this article. The direction of the wear scar (wear angle) is determined based on angle transformation and grey consistency (the smallest change of grey level). Simulation results show that the algorithm has high precision, good robustness and less time consuming. The average absolute error of our method is 0.8° and the absolute error of 95% of samples is <4°. The average runtime per frame is 3.896 s in the simulation platform.

Tribological Properties of Al2O3 Nanoparticles as Lithium Grease Additives

The tribological properties of Lithium grease specimens with different concentrations of Al2O3 nanoparticles were investigated using a pin on disc apparatus under different sliding speeds and normal loads. Results showed that Al2O3 nanoparticles enhanced the tribological properties of lithium grease and reduced the COF and wear scar width by approximately 57.9% and 47.5% respectively.