Tribological performance of commercial Mobil grade lubricants operating with titanium dioxide nanoparticle additives

Purpose The purpose of this study is to investigate the tribological performance (anti-friction and anti-wear properties) of commercial Mobil grade lubricants used in a journal bearing system in a power plant. Design/methodology/approach Three grades of Mobil lubricants (DTE 24, DTE 25 and DTE 26) are considered during the study. Titanium dioxide nanoparticles (TiO2, 0.5 Wt.%) of size 40 nm are used as a lubricant additive to examine the performance of the lubricants. The viscosity of the lubricant is computed using modified Krieger–Dougherty viscosity model. The morphology of TiO2 nanoparticles is studied with the help of scanning electron microscopy, ultra violet spectrophotometer and X-ray diffraction. The study of antifriction and antiwear properties for lubricants is carried out on four-ball tribo-tester for operating conditions specified by ASTM standards. Findings The tribochemical reaction film is formed between ball surfaces during the experiments on four-ball tester that minimizes the asperity contact due to addition of TiO2 nanoparticles in the lubricant. The viscosity of the lubricant is enhanced due to the addition of TiO2 nanoparticles. The frictional coefficient and wear scar diameters of balls in the lubricants are reduced in the range of 6-26 and 2-7 per cent, respectively. Originality/value The tribological properties of TiO2 as a lubricant additive in three commercial Mobil grade lubricants are investigated in this paper. The results obtained in this paper are expected to be helpful to bearing designers, researchers and academicians concerned with the relevant study.