Analysis of fluorinated interactions in plain ZDDP and fully formulated oils using design of experiment (DOE) and chemistry characterization of tribofilms in boundary lubrication under extreme loading conditions

Abstract

Purpose – The purpose of this paper is to describe very reproducible boundary lubrication tests, conducted as part of design of experiment (DOE) to study the behavior of fluorinated catalyst mixed with polutetrafluoroethylene or Teflon (PTFE) in developing environmentally friendly (reduced P and S) anti-wear additives for future engine oil formulations. The paper presents both the statistical and experimental solution to the fluorinated interactions in fully formulated (F-fully formulated) and plain ZDDP (F-plain) oils. Design/methodology/approach – The wear performance of fluorinated additive in combination with conventional commercial oil and ZDDP plain oil were investigated using DOE software. Several chemistry combinations were prepared and tested under extreme boundary lubrication (385 N with maximum Hertzian contact pressure of 2.72 GPa). Wear and frictional properties were evaluated using DOE and the interactions of fluorinated mix with minimum phosphorus were studied and compared with respect to fully formulated and plain ZDDP oils. Findings – The optimized desirability shows the best condition that leads to more consistency in the breakdown of the tribofilm for a fixed contact load and fixed amount of fully formulated ZDDP oil. 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. Originality/value – To ensure the reliability of the model, two original tests were conducted on the fully formulated and plain oil with minimum fluorinated mix.