Abstract
Overbased calcium sulfonate (OBCS) has been added as a detergent to lubrication oil. Under boundary lubrication condition, it is known that OBCS forms a tribofilm on rubbing surface. Therefore, OBCS affects the tribological properties directly. For understanding of the properties of the tribofilm, the relation between formation and peeling was investigated by in-situ film thickness measurement. The results indicated that film peeling was accelerated by switching base fluid from poly-α-olefin (PAO) into poly-ol-ester (POE). It can be concluded that polarity of POE accelerated the peeling. Furthermore, the thickness of tribofilms is determined by the balance of formation and peeling rates.
