Tribological investigation of sunflower and soybean oil with metal oxide nanoadditives

Abstract

Mineral oil-based lubricants have lack of degradability, resulting in environmental hazards and natural loss when disposed of it in the environment. Therefore, replacing these mineral oil-based lubricants with renewable and biodegradable lubricants has become necessary due to various health issues and limited availability. The present work discusses the synthesis, antiwear, and antifriction behavior of vegetable oil-based nanolubricants. The two different nanoparticles, CuO and ZrO2, have been added separately with varying concentrations (0.25% as low, 0.50% as medium, and 0.75% w/w as high) as nanoadditive in two different vegetable-based base oils, i.e., sunflower and soybean oil. Formulation of these nanolubricants was carried out with a magnetic stirrer followed by ultrasonication for 1 h. Friction and wear behavior was investigated using four ball tester tribometer. All tests were conducted according to ASTM standards. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectroscopy (EDS) were used to examine worn surfaces. The results show that addition of CuO nanoparticles in both sunflower and soybean oil improved antifriction behavior with a reduction in coefficient of friction of 35.10% and 39.39%, respectively. Furthermore, addition of ZrO2 nanoparticles to soybean oil yields no improvement, whereas adding ZrO2 nanoparticles to sunflower oil yields a 27.64% reduction in coefficient of friction and 24% reduction in wear scar diameter, respectively. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.