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

Abstract

In this study, tribological properties of custom formulated and stabilized nano lubricant are investigated. Spherical CuO nanoparticles are suspended in 20W-50 mineral base lubricant using Oleic Acid (OA) as a surfactant. Three different nano lubricant concentrations with 0.2, 0.5, and 1 wt.% were analyzed through ASTM G-99 pin-on-disc tribometer standardized test under boundary/mixed lubrication regimes. The generated friction and wear analyses confirm a consolidation of tribological properties with a reduction in friction coefficient in the range of 14.59–42.92%, compared with the base lubricant. Analysis of worn surfaces (SEM/EDX) as well as (AFM) was conducted. Combined hypotheses were proposed from the analysis of worn surfaces; these hypotheses suggested that CuO nanoparticles exhibit an integrated effect of two phenomenal lubrication mechanisms. Additionally, dispersion stability evaluation of the suspended nanoparticles was performed through Zeta potential, (FTIR), and sedimentation analyses. Stability results showed that steric stabilization is the dominating effect of the repulsive forces between nanoparticles, surpassing the electrostatic repulsive forces.

Tribological Behavior of Ionic Liquid with Nanoparticles

“…With rolling friction, the contact areas and shear stress at contact decrease, which leads to the reduction in friction coefficient and wear. This rolling effect of the third body mechanism in friction reduction has been proven by theoretical [ 38 ] and experimental results [ 20 , 25 , 39 ]. In summary, the lubrication mechanisms of CuO and ZnO nanoparticles in the ionic liquid are tribo-sintering and third body with rolling effects, respectively.…”

“…Among all nanoparticles, copper oxide (CuO) and zinc oxide (ZnO) have been widely researched due to their excellent tribological properties. The addition of CuO nanoparticles could reduce friction and wear when they were blended into different types of lubricating oils [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. For instance, Kumar et al [ 14 ] presented that the CuO nanoparticles could be mixed with the zinc dialkyldithiophosphates (ZDDP) additive to increase the wear resistance ability of vegetable oil.…”

“…Moreover, the CuO nanoparticles were compatible with engine oils and resulted in significant friction reduction [ 18 , 19 ]. A reduction in friction coefficient by 37.9%, 42.9%, and 14.6% for three different concentrations of 0.2, 0.5, and 1.0 wt%, respectively, was observed when CuO nanoparticles were added to a mineral-based lubricant [ 20 ]. Reference [ 21 ] showed that the addition of CuO nanoparticles to grease could decrease the friction coefficient and wear scar diameter significantly.…”

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

“…CuO and ZnO nanolubricants had been investigated extensively, based on their rheological and tribological properties. They offered a remarkable intensification to both characteristics compared to other oxides, whether as a single [52,72,126,130] or hybrid additive [73,77]. Likewise, from the family of oxides, the hybrid Al 2 O 3 /TiO 2 nanolubricant showed a valuable performance at the level of tribological, thermal, and dispersion stability properties [50].…”

“…For instance, it had been reported by Abdel-Rehim that CuO would aggregate at a high concentration of 1 wt.% [52]. These aggregates led to instability of tribo-film formation, which had been demonstrated through the surface analysis of EDX.…”