Frictional performance evaluation of sliding surfaces lubricated by zinc-oxide nano-additives

ABSTRACT

Automobile engines consume more than 30% of fuel energy as frictional power waste. Therefore, this paper investigated the tribological properties of ZnO nanoparticles (NPs) as a nano-additive to improve the wear and friction trends of the piston ring/cylinder liner interface, especially in boundary lubrication. This improvement occurs due to the formation of a solid tribofilm layer on the sliding surfaces that acts as an indirect coating to help separate and protect the worn pairs. Tribological experiments were carried out under different speeds and loading circumstances using a ring-on-liner reciprocating test bench. The surface morphologies of the tested samples were analysed using EPMA, FE-SEM, a 3D surface profilometer and XPS to illustrate the key mechanisms of the ZnO nano-additives. The tribotest results show that the coefficient of friction and specific wear rate of the ring were reduced by 20–23% and 43–88%, respectively, using the ZnO nano-additives compared with the reference oil.

KEYWORDS:

• Sliding friction
• piston ring/cylinder liner contact
• ZnO nano-additives
• anti-wear/friction

Acknowledgements

The authors also wish to thank the editors and reviewers for their precious time and valuable suggestions and comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Mohamed Kamal Ahmed Ali http://orcid.org/0000-0002-5652-0262

Additional information

Funding

The authors would like to express their deep appreciation to the financial support from the National Natural Science Foundation of China (NSFC), Project No. 51875423. The authors also acknowledge the continuous support of Hubei Key Laboratory of Advanced Technology for Automotive Components (Wuhan University of Technology). A. Elagouz gratefully acknowledges the financial support from both the Chinese Scholarship Council (CSC grant number 2016GF124), China and the Minia University, Egypt. Dr. M.K.A. Ali gratefully acknowledges the financial support during the post-doctoral study from Minia University, Egypt.