Abstract
In this study, the tribofilm formation process lubricated with an engine formulated oil was investigated using a lab-built in-situ Raman-SLIM (Spacing Layer Imaging Method) multi-analytical tribometer. The tribometer can simultaneously analyze the chemical composition and film thickness of tribofilms on the worn surface. The tribological test was conducted at DLC/Steel (disk/ball) tribopairs lubricated with the fully-formulated oil with zinc dialkyldithiophosphate and molybdenum dithiocarbamate. From the results, there is a distribution of the tribofilms and a difference of the tribofilm thickness on the steel surface. It should be noted that the chemical characterization of the tribofilms depends on their film thickness. The thicker tribofilms have richer MoS2 and higher P-O-P rate phosphate glasses. On the other hand, the thinner tribofilms have richer MoOx and lower P-O-P rate phosphate glasses. Therefore, there is a correlation between the film thickness and the chemical characterization of the tribofilms, and in-situ Raman-SLIM analysis method is an effectiveness for monitoring for the factors.
