Fluorinated FeF3 catalyst interactions in three different oil formulations using design of experiment optimization and chemistry characterization of tribofilms

Abstract

The influence of fluorinated FeF3 catalyst on the formation and properties of tribofilms was examined using design of experiment (DOE) under extreme boundary lubrication (385 N or maximum Hertzian contact pressure of 2.72 GPa). A closed loop boundary condition test was developed to examine the behaviour of lubricants under boundary conditions. The reduction of phosphorus in engine oil was examined using two different plain oils and one fully formulated oil. Results indicate the formation of a thicker tribofilm in plain fluorinated oil when compared with fluorinated fully formulated oils. Several chemistry combinations were prepared and tested. Wear and frictional properties were evaluated using DOE, and the interactions of fluorinated FeF3 catalyst with minimum phosphorus were studied and compared with respect to fully formulated and plain zinc dialkyl dithiophosphate oils. Tribofilms with thickness ranging from 150 to 350 nm were developed during wear tests and were analysed for fluorinated plain and fully formulated oils that target reducing phosphorus. Three specific tests with optimised 0.6% FeF3 catalyst concentrations were used with 0.05% phosphorus in plain and fully formulated oil to verify the model optimised conditions with respect to wear and time to full break down. Scanning electron microscopy, hardness of the tribofilms and Auger spectroscopy confirm the presence of fluorine and phosphorus. These tests confirm the optimised prediction of the DOE model.