Effects of Nano-TiO₂ Additive in Oil-in-Water Lubricant on Contact Angle and Antiscratch Behavior

ABSTRACT

Contact angle and scratch tests have been conducted to investigate the effects of nano-TiO₂ additive in oil-in-water (O/W) lubricant. The results show that the contact angle between high-speed steel with oxide scale and 1% (oil concentration) O/W lubricant decreases first and then increases as the concentration of nano-TiO₂ particle in the O/W lubricant increases. The smallest contact angle is obtained after an addition of 4% nano-TiO₂ additive to the O/W lubricant. This is because the nano-TiO₂ can enhance the surface excess of the oil when the nano-TiO₂ particles distribute throughout the surface of the oil droplets, and after saturation they can distribute throughout the water and also improve the surface excess of the water in the O/W lubricant. The scratch and hot rolling tests show that the nano-TiO₂ particles in the O/W lubricant can also reduce friction, improve scratch resistance, and reduce rolling force. A method for measuring the adhesion force of the oxide scale is proposed and the effect of nanoparticles is discussed. It is demonstrated that the effect of self-lubrication of nanoparticles in the O/W lubricant plays a more significant role in the tribological behavior during hot rolling than wettability.

KEYWORDS:

• Nano-TiO₂ additive
• oil-in-water lubricant
• contact angle
• scratch resistance

Acknowledgements

The authors are grateful for the assistance of Dr. Madeleine Strong Cincotta in the final language editing of this article. We also acknowledge use of facilities within the UOW Electron Microscopy Centre.

Funding

The authors gratefully acknowledge financial support from the University of Wollongong and China Scholarship Council (CSC).