Purpose With rising demand for energy-efficient and durable mechanical systems, the search for advanced lubrication strategies has gained momentum. This study aims to explore the tribological performance of AISI 52100 bearing steel surfaces lubricated with conventional mineral oil modified by copper oxide (CuO) nanoparticles. Experiments were carried out using a four-ball tribotester to simulate real-world loading and evaluate the effectiveness of nanoparticle-enhanced lubrication. Design/methodology/approach CuO nanoparticles were dispersed into base oil at concentrations of 0.05%, 0.1%, 0.25% and 0.5%. The influence of these concentrations on the coefficient of friction (COF) and wear scar diameter (WSD) was analyzed. Characterization techniques such as high-resolution transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy were used to assess nanoparticle morphology, structure and composition. Tribological tests followed ASTM D4172 B standards. Findings Results revealed significant enhancement in tribological behavior with CuO addition. The 0.1 Wt.% concentration yielded the best performance, reducing COF by 65.94 ± 1.51% and WSD by 41.10 ± 1.45% over base oil. This concentration offered optimal nanoparticle dispersion and effective tribofilm formation, improving lubrication through a rolling/sliding mechanism at the contact surface. Originality/value This study highlights the potential of CuO-based nanolubricants in reducing friction and wear. Identifying an optimal concentration supports future development of efficient, scalable lubrication solutions, with direct implications for enhancing performance and reliability in industrial systems. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2025-0246/
Singh et al. (2025) studied this question.