This paper is to evaluate and compare the tribological properties of lubricating oil blends added with nano graphene and lubricating oil blends added with cerium oxide (CeO2) on the key friction pairs of the diesel engines. The dispersion stability is the premise of studying the tribological properties. In this paper, nano-CeO2 particles were self-made and high-quality nano-graphene was purchased. The dispersion stability of the two nanomaterials in lubricating oil was studied after the same modification respectively. According to the working conditions of the cylinder liner and the piston ring, the friction and wear tests of the lubricating oil blends added with the modified nanomaterials were carried out at the different temperatures. The results showed that the oleic acid and the stearic acid modified the two nanomaterials successfully. The dispersion stability of the modified nanomaterials in lubricating oil was improved. The dispersion stability of the lubricating oil blends added with graphene before and after modification was slightly higher than that of lubricating oil blends added with CeO2 before and after modification, respectively. At the high temperature, the anti-friction property of the two nano lubricating oil blends was similar. At the ambient temperature, lubricating oil blends added with modified CeO2 did not play a role in reducing friction, while lubricating oil blends added with modified graphene had the effect of reducing friction. Whether at ambient temperature or at the high temperature, the anti-wear property lubricated with lubricating oil blends added with modified CeO2 within the right concentration range was better than that lubricated with lubricating oil blends added with modified graphene.
Good dispersion stability of lubricating oil blends added with graphene is the premise of playing its superior tribology property. In this paper, the dispersion stability of modified graphene in lubricating oil and the wear property of nanolubricating oil on the key friction pair for a diesel engine was studied by simulation and experiment. The results showed that the dispersion of modified graphene in lubricating oil was improved at ambient temperature and pressure and at high temperature and pressure. However, the dispersion effect of graphene at high temperature was slightly worse than that at ambient temperature. The wear property of lubricating oil blends added with modified graphene with a concentration of no more than 100 ppm was improved. With the increase of graphene addition, the wear reduction effect increased first and then decreased. The lubricating oil blend added with 25 ppm modified graphene is the best for wear reduction.
Purpose The purpose of this paper was to improve the frictional wear resistance properties of piston skirts caused by the low viscosity lubricant by studying the tribological performance of three novel coating materials. Design/methodology/approach Comparative tribological examinations were performed in a tribological tester using the ring-block arrangement under two viscosity lubricants, the loading force was applied as 100 N, the speed was set to 60 r/min and the testing time was 180 min. Findings Under low viscosity lubricant, the friction coefficient and wear of the three coatings all increase, and the friction coefficient and wear of the PTFE coating are the largest, while the MoS2 coating has the lowest friction coefficient and wear. Under low viscosity lubricant, the friction coefficient of the MoS2 coating is 2.1%–5.4% and 20.0%–24.3% lower than that of the SiO2 and PTFE coating, respectively. The friction coefficient and wear fluctuation rate of the MoS2 coating is the smallest when the lubricant viscosity decreases, which indicates that the MoS2 coating has excellent stability and adaptability under low viscosity lubricant. Originality/value To reduce the piston skirt wear caused by low viscosity lubricant in heavy-duty diesel engines, the friction and wear adaptability of three novel composite coating materials for piston skirts were compared under 0 W-20 low viscosity lubricant, which could provide a guidance for the application of wear-resistant materials for heavy-duty diesel engine piston skirt.
This paper aims to evaluate the impact of different qualities of nano‐cerium dioxide (CeO2) as the diesel additives on the friction and wear performance of the fuel injection system. Two different qualities of nano‐CeO2 were selected to prepare stably dispersed CeO2‐diesel blends. Their effects on the tribological behaviour of the injector body were studied on the RTEC friction tester. The results showed that the friction and wear properties of diesel blend with 10 ppm of CeO2 (whether CeO2‐1 or CeO2‐2) were all improved compared with pure diesel. With the increase of CeO2 addition (>10 ppm), the friction coefficient, wear width, and maximum wear depth of the wear scar increased. Compared with the blocky CeO2, adding spherical CeO2 into diesel had better friction and wear properties. Adding 10 ppm of CeO2 to diesel has no negative impact on the friction and wear performance of the injector body, especially the spherical CeO2.
Ultra‐high molecular weight polyethylene (UHMWPE) powder was modified by surface treatment technology, then its wettability, dispersibility, mechanical, and tribological properties in polyurethane elastomer were studied. The testing results showed that after surface treatment, UHMWPE powder could infiltrate and disperse evenly in polyurethane, and build micro cross‐link with the contact surface of polymer substrate, which is conducive to enhancing the internal stress of polymer and improving the mechanical properties. With a small amount of modified UHMWPE being added into the casting polyurethane (CPU) elastomer, the right‐angled tearing strength increases and the abrasion loss decreases. Moreover, the elastomer surface self‐lubricating performance of CPU compounding with modified UHMWPE is enhanced: compared with the neat CPU sample, the average friction coefficient of the CPU samples with 5%, 10%, and 15% of modified UHMWPE is reduced by 46.3%, 41.5%, and 39.0%, respectively, and the surface wear resistance is improved; under the high‐load working condition, the CPU elastomer with 5% of modified UHMWPE has the optimal tribological performance.
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