Current Issue : January - March Volume : 2016 Issue Number : 1 Articles : 7 Articles
This paper used graphite nanoparticles with the diameter of 35 and 80 nm and LB2000 vegetable based oil to prepare graphite\noil-based nanofluids with different volume fractions by two-step method. The tribological properties of graphite nanoparticles as\nLB2000 vegetable based oil additive were investigated with a pin-on-disk friction and wear tester. Field emission scanning electron\nmicroscope (FE-SEM) and energy dispersive spectroscopy (EDS) were used to examine the morphology and the content of some\ntypical elements of wear scar, respectively. Further, the lubrication mechanism of graphite nanoparticles was explored. It was found\nthat graphite nanoparticles as vegetable based oil additive could remarkably improve friction-reducing and antiwear properties\nof pure oil. With the increase of volume fraction of graphite nanoparticles, the friction coefficient and the wear volume of disk\ndecreased. At the same volume fraction, the smaller particles, the lower friction coefficient and wear volume.The main reason for\nthe improvement in friction-reducing and antiwear properties of vegetable based oil using graphite nanoparticles was that graphite\nnanoparticles could form a physical deposition film on the friction surfaces...
Tribological properties of surfaces (friction,\nadhesion and wear) provide challenging limitations to the\ndesign of reliable machines on the micro- and nanometer\nscale as the surface to volume area increases and volume,\nmass and inertia of the mobile parts decrease. This study\nreports on the reduction in the friction force of silicon\nsurfaces after the alkali metal ion exposure in the form of\naqueous solutions. A scanning force microscope equipped\nwith a liquid cell was used to investigate the friction force\nand the pull-off force of a flat silicon surface immersed in\nwater and in different alkali metal chlorides solutions:\nLiCl, NaCl and CsCl. The concentration ranged from 0.1\nup to 1000 lmol/l. The changes in the free surface energy\nof the initial surface and of the modified surfaces after\ndrying were determined from contact angle measurements\nand from the acidââ?¬â??base adhesion theory. In both cases, in\nthe liquid environment and after drying of the exposed\nsilicon substrates in air, the friction force is reduced by\napproximately 50 %. Our results provide new, fundamental\ninsight into the exchange of surface termination layers in\nparticular for tribology. Also it is suggested to use the\nprocedure as a low-cost alternative to improve the tribological\nproperties of the silicon surface in particular in\napplications where lubricating fluids are not appropriate,\ne.g., in nanomachines and devices....
DLC coatings are currently used in a wide variety of industrial fields because of their outstanding properties such as high hardness, high wear resistance, low friction and so on under oil lubrication as well as no lubrication. In order to evaluate the tribological performance of DLC coatings under water lubrication, eight types of DLC coatings were evaluated by water-lubricated sliding tests at sliding velocities of 0.02 m/s and 0.1 m/s. The different DLC coating types comprised both hydrogenated and hydrogen-free DLC films that were deposited using different techniques: amorphous hydrogenated DLC (a-C:H), that doped with tungsten (a-C:H:W), that doped with silicon (a-C:H:Si) and hydrogen-free DLC (ta-C). DLC coatings showed low friction coefficient and excellent wear resistance. Friction coefficient and wear rate decreased with increasing sliding velocity. The effect of surface wettability and mechanical properties on tribological characteristics was investigated. Friction coefficient decreased as the contact angle increased. Hydrogen-free DLC coating with the highest hardness showed the highest friction and a larger wear rate. Furthermore, DLC coatings deposited with interlayer showed longer lifetimes....
The spike forging test is still commonly used although there are some new tribology test methods, but each designer\nwould like to give their own parameters. Considering the spike height difference between low friction and high friction\nas the evaluation index, an optimal spike forging test developed using finite element simulations based on orthogonal\noptimization method and sensitivity analysis of tribological conditions of selected key design parameters was carried out.\nThe spike height does not always monotonically decrease with the increase in friction factor in the scheme with improper\nparameters; therefore, the design of spike forging test should be critically evaluated before assessing tribological conditions.\nAccording to the optimized parameters, a simplified set-up of spike forging test was designed, and two retainers\nwith a clearance fit and the billet with a chamfer were prepared to position the test billet. Finally, four different tribological\nconditions, including dry polytetrafluoroethylene lubricant, multipurpose grease, VG32 oil, and dry condition, in aluminum\nforging were chosen as a case study for the optimized design of spike forging test, and correspondingly, the\nlubricating effect was distinguished....
Boron nitride film was deposited on h1 0 0i-oriented silicon substrate by hot filament assisted chemical\nvapor deposition. The B[N(CH3)2]3 (Tris(dimetylamino)borane, TDMAB) was used as the single source precursor\nboth for boron and nitride, and ammonia gas was used as the extra source to increase the N concentration in the films.\nElemental composition of the films deposited under different filament temperatures were measured by energy dispersive\nX-ray (EDX) analysis, and the structure of the films were measured by X-ray diffraction (XRD) and Fourier transform\ninfrared spectroscopy (FT-IR). The boron nitride films deposited under lower filament temperature was\namorphous, while BN films contain hexagonal structure were deposited at higher filament temperature. To verify\nwhether the films can be applied to the microforming die, a ball on disk test was carried out using pure titanium ball\nas the counterpart to investigate the interfacial behavior between the films and pure titanium. The results show that the\nreaction between the films and pure titanium was low as there was no titanium adhesion on the wear track when the\nfilm was remained....
In this study, we synthesized two types of calcium sulfonate complex greases (barium soap and\ncalcium soap) and investigated their physical, rheological, and tribological properties in detail. The test results\nshowed that the evolution of their linear viscoelasticity functions with frequency were quite similar to those of\ntraditional lubricating greases. Moreover, these two calcium sulfonate complex greases had good friction reducing\nand antiwear properties at room temperature and at 150 �°C. In addition, by adding an organic\nmolybdenum compound (MoDTC) to the base greases, we obtained a very low friction coefficient (0.065) for\none of the greases (calcium soap) at 400 N and 500 N (maximum Hertzian pressures of 3.47 GPa and 3.74 GPa,\nrespectively) at 150 �°C. X-ray photoelectron spectroscopy (XPS) analysis showed that the tribofilm was composed\nof some complex oxide species and CaCO3 that had formed on the worn surface....
During operation of machines their moving parts have rotating and translating motion. The motion\nbetween two surfaces is accompanied by wear. Hard wear-resistant coatings based on Cr have been\nused to increase wear resistance of these parts. Methods for determining the tribological properties of\nsurfaces can be categorized according to the type of relative movement of the tested material and the\napplied bodies and the method of contact and his geometry. One of the methods most frequently used\nfor determination of tribological properties of surfaces is the ââ?¬Å?Pin-on-Discââ?¬Â method. This paper deals\nwith analysis and comparison of tribological properties and surface of two types of Cr coatings after\nthe tribo test. The tested Cr coatings were deposited by PVD technology (CrPVD) and by\nelectrochemical (galvanic) method (Crgalv). Results of tribological tests showed that maximum depth\nââ?¬Å?hââ?¬Â and width ââ?¬Å?wââ?¬Â of the wear track was observed on the galvanic Cr coating with lower hardness....
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