Tribological evaluation of PAO 100 oil‐based lithium greases with chemically functionalized nanoadditives

Abstract

AbstractThe lubricating greases employed in this study were formulated with polyalphaolefin (PAO) 100 as the base oil and 12‐lithium hydroxystearate as the thickener. The sol–gel method was used to produce the LaF3 nanoadditives. The oleic acid‐treated LaF3 (i.e., OA‐LaF3) and carboxylic acid‐treated MWCNTs (i.e., COOH‐MWCNTs) were blended in the formulated grease samples and used as nanoadditives. The detailed microstructural and chemical properties of chemically treated nanoadditives were investigated using HR‐TEM, XRD, FTIR and XPS analyses. Using a four‐ball tester, the effect of different concentrations of nanoadditives on the tribo‐performance of greases was investigated. Tribo‐test results revealed the role of nanoadditives in PAO‐based grease lubrication performance. COOH‐MWCNTs and OA‐LaF3 nanoadditives outperformed PAO grease in terms of physicochemical and tribo‐performance for steel‐steel tribo‐pair. The improved tribo‐performance is attributed to the formation of tribo‐film on the contact interfaces via nanoadditives. The development of tribo‐film was confirmed by XPS analysis of worn surfaces.