Comparison Between the Action of Nano-Oxides and Conventional EP Additives in Boundary Lubrication

Abstract

Additives are essential in lubricant development, improving their performance by the formation of a protective film, thus reducing friction and wear. Some such additives are extreme pressure additives. However, due to environmental issues, their use has been questioned because their composition includes sulfur, chlorine, and phosphorus. Nanoparticles have been demonstrated to be a suitable substitute for those additives. This paper aims to make a comparison of the tribological performance of conventional EP additives and oxides nanoparticles (copper and zinc) under boundary lubrication conditions. The additives (nanoparticles, ZDDP, and sulfur) were added to mineral and synthetic oils. The lubricant tribological properties were analyzed in the tribometer HFRR (high frequency reciprocating rig), and during the test, the friction coefficient and percentual of film formation were measured. The wear was analyzed by scanning electron microscopy. The results showed that the conventional EP additives have a good performance owing to their anti-wear and small friction coefficient in both lubricant bases. The oxides nanoparticles, when used as additives, can reduce the friction more effectively than conventional additives, and displayed similar behavior to the extreme pressure additives. Thus, the oxide nanoparticles are more environmentally suitable, and they can replace EP additives adapting the lubricant to current environmental requirements.

Tribological Behavior of Ionic Liquid with Nanoparticles

“…This deposition can compensate for the mass loss on the contact surfaces by the "mending effect". This mechanism of CuO nanoparticles was reported in previous research, where CuO nanoparticles were used as an additive in synthesis oil [25].…”

“…Similar to CuO, ZnO nanoparticles have been used as additives for improving the tribological behavior in many types of lubricating oils [ 22 , 23 , 24 , 25 , 26 ]. Mana et al [ 22 ] reported that the addition of ZnO nanoparticles in mineral-based oil showed better friction reduction ability than the commonly used anti-wear additives ZDDP.…”

“…The ZnO nanoparticles combined with diesel oil could improve the thermophysical properties of diesel oil [ 23 , 24 ]. Mello et al [ 25 ] made a comparison of the tribological performance of ZDDP, CuO, and ZnO when used as additives in mineral and synthetic oils. The results showed that the additions of CuO and ZnO nanoparticles could reduce friction more effectively than ZDDP additives.…”

Recent Advances in Preparation and Testing Methods of Engine-Based Nanolubricants: A State-of-the-Art Review

“…Plenty of nanomaterials have been used for this objective. This includes carbon and its derivatives (Gr [26], MWCNT [27], ND [28,29]), oxides of inorganic compounds (ZnO [30,31], CuO [32] MgO [33], TiO 2 [34]), and transition metal dichalcogenide (MoS 2 [35]).…”

Investigation of the Tribological Behavior of Mineral Lubricant Using Copper Oxide Nano Additives

“…A recent study was conducted with CuO and ZnO with a concentration of 0.5 wt.% compared with the commonly used anti-wear additive ZDDP [10]. Both of the nanoparticles showed a considerable tribological enhancement regarding friction reduction and antiwear behavior.…”