Rheological and Film Forming Behavior of the Developed Nanocomposite Greases Under Elastohydrodynamics Lubrication Regime

Abstract

Performance of grease lubricated point contact under elastohydrodynamics lubrication (EHL) regime is critical in many engineering applications. The present work deals with the evaluation of rheological, film forming characteristics and elastic recovery of newly developed nanocomposite greases. The nanocomposite greases are formulated by dispersing different nano-additives to bare grease (BG). The nano-additives include reduced graphene oxide (rGO) nanosheets, CaCO3 and α-Al2O3 nanoparticles. The microstructure evaluation of the nano-additives and different greases is done using high-resolution transmission electron microscopy (HRTEM). Estimation of the rheological parameters (storage and loss moduli) is done using rotational rheometer. The film forming behavior is recorded using elastohydrodynamic (EHD) rig for range of speed at different temperatures and constant load. The results indicate that change in microstructure due to nano-additive incorporation improves the responses of different greases. Based on rheological response, CaCO3 doped grease seems better but rGO doped grease is able to bear high shear stresses. Further, based on film forming characteristics and reflow or recovery behavior, rGO doped grease is better. The rGO-based grease registers approximately 90% elastic recovery followed by 75% for CaCO3-based grease, 65% for BG and 10% for α-Al2O3-doped grease.