The effect of FeF3/TiF3 catalysts on the thermal and tribological performance of plain oil ZDDP under extreme pressure loading

Oil and engine lubricant are complex products consisting of detergent, dispersant, antiwear additives, and viscosity improver. Many of these ingredients can interact and influence the mechanism of tribofilm formation and breakdown. This paper addresses the friction and wear performance of ZDDP plain oil additives (0.1% phosphorus) with (iron fluoride FeF3 + titanium fluoride TiF3) catalysts and polytetrafluoroethylene PTFE using thermal and tribological analysis. Thermal tests and tribological tests were performed using thermogravimetric analysis (TGA), X-ray Photoelectron Spectroscopy (XPS), and ball on cylinder wear apparatus. The tribological data were collected and Design of Experiment (DOE) was used to optimize the load and oil quantity with respect to surface finish. Data analyzed by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) on optimized samples showed that 0.1 μm Ra surfaces tribologically tested with ZDDP, catalyst and PTFE performed better under an optimized load of 307 N (2.53 GPa Hertzian contact pressure), especially when 2 different rotational speeds are used (100 rpm for the first 5000 revolutions then 700 rpm until 100,000 revolution or failure whichever comes first). Thermally treated surfaces show better coating in the presence of TiF3 and FeF3 with PTFE. The transfer of coating material under extreme pressure improved the antiwear resistance of the additives, and was shown to have an influence on the friction and wear performance.