Friction and Wear Reduction Mechanisms of the Reciprocating Contact Interfaces Using Nanolubricant Under Different Loads and Speeds

Abstract

This study aims to reveal the roles and mechanisms of Al2O3/TiO2 hybrid nanoparticles into the lube oils which could reinforce engine components durability via reducing the friction, wear, or fuel economy in automotive engines. The tribological tests were carried out under different sliding speeds from 0.21 to 1.75 m/s and loads from 30 to 250 N using a reciprocating tribometer to simulate the ring/liner interface in the engine according to ASTM G181. The tribological results using hybrid nanolubricants suggested that the friction coefficient and wear rate of the ring decreased in the ranges 39–53% and 25–33%, respectively, compared to nanoparticles-free lube oil. The combined evidence of the worn surfaces analysis confirmed that the key mechanisms in antifriction and antiwear are a combination of the nanoparticles rolling mechanism and the replenishment mechanism of tribofilms on the sliding contact interfaces. In addition, a tribofilm formed on the rubbing surfaces is not only from the nanoparticles but also from Fe which is formed as a result of iron debris particles and oil additive package such as P and S originating from zinc dialkyldithiophosphate.