Tribological property of TiO2 nanolubricant on piston and cylinder surfaces

In this paper, an arc spray nanofluid synthesis system with complex ultrasonic orthogonal vibration and vortex stirring was proposed and developed for TiO2 nanolubricant, in which TiO2 nanoparticles were of equal roundness and consistent size. In the proposed nanofluid synthesis system, one of the electrodes and ultrasonic vibrator were assembled to form an orthogonal model with another electrode installed inside the vacuum chamber of arc discharge system, with 10 W/30 lubricant serving as the dielectric liquid. The tribological behavior of the lubricant with TiO2 nanoparticles at average particle size 25 nm on the surface of piston ring is compared with that of the lubricant without TiO2 nanoparticles. Experimental results showed that the coefficients of friction between the piston ring and base lubricant was 0.15; between the piston ring and TiO2 nanolubricant was 0.14. Furthermore, the piston ring's wear rates of the base lubricant and TiO2 nanolubricant were 0.0055 and 0.0021, respectively. After operating the piston cylinder for 8 consecutive hours in 15 and 30 days, respectively, the diameter of TiO2 nanoparticles in the lubricant remained 25 nm in average. As observed from the piston ring surface on the 15th and 30th days through scanning electron microscope (SEM), it had less scraping than the piston lubricated without TiO2 nanoparticles. Therefore, a lubricant added with TiO2 nanoparticles can better protect the piston ring surface.