Fluorinated interactions in two different plain ZDDP oils using design of experiment (DOE) and chemistry characterization of tribofilms

Abstract

Purpose – The purpose of this paper is to study the friction and wear performance of two plain ZDDP oils in the presence of fluorinated catalyst and PTFE combinations under extreme boundary lubrication of 385 Newton load (Hertzian contact pressure of 2.72 GPa). The mechanism of tribofilm formation and breakdown was followed carefully by monitoring the friction coefficient over the duration of the test. Design/methodology/approach – Very reproducible boundary lubrication tests were conducted as part of design of experiment (DOE) to study the behavior of two different fluorinated plain oils in developing environmentally friendly (reduced P atd S) anti-wear additives for future engine oil formulations. Friction and wear performance of ZDDP plain oils improve in the presence of fluorinated mix combinations. In order to understand the wear mechanism, different factors of chemical compositions and different wear responses were analyzed and optimized using DOE. Several chemistry combinations were prepared and tested under extreme boundary lubrication. Findings – The interactions of fluorinated mix with minimum phosphorus were studied and compared. Tribofilms with thickness ranging from 300-400 nm were developed during wear tests and were analyzed for two fluorinated plain oils that target reducing phosphorus. Originality/value – The influence of catalyst and PTFE fluorinated mix were examined. Scanning electron microscopy with chemistry analysis was developed. Hardness of the tribofilms, X-ray of the wear track and Auger spectroscopy confirm the present of fluorine and phosphorus. The two repeated tests that were conducted on both plain oils with minimum fluorinated mix confirm the prediction of the DOE model.