Tribo-dynamic performance of newly developed environmentally friendly lubricating greases containing nano-CaCO3

The present study explores the performance of novel vegetable oil-based greases containing nano-CaCO3 as an additive. A series of greases with varying nanoparticle concentrations (0 – 4 %w/w) are evaluated on a four-ball tester machine under a standard tribological test (ASTM D2266) and simultaneously in a rolling bearing at various speeds and loads against two commercial greases as the benchmark. The vibrations and shock pulse measurements (SPM) are recorded to assess the bearing performance. The tribo-dynamic investigation suggests that the eco-friendly nano-greases are at par with the commercial ones; the performance varies with the nanoparticle concentration. Under the tribological test, the third-body action of nanoparticles seems to increase friction, while the interfacial deposition (physisorption) of nano-CaCO3 and nano-CaO decreases wear. Under the bearing test, the rolling effect of nanoparticles seems to influence the vibrations, while their entrainment in the contact zone governs the carpet values. The nano-grease containing 4% nano-CaCO3 performs best under both assessments, displaying great prospects of a sustainable and potential alternative to existing environmentally unfriendly greases.