Fluorinated mix in plain ZDDP oil and commercial oil using design of experiment analysis of all interactions and fundamental study of fluorinated mix in plain ZDDP oils under 2 different r/min test cycles and extreme boundary lubrication

Abstract

Wear performance of engine oil was studied in the presence of submicron iron fluoride (FeF3) and polytetrafluoroethylene (PTFE) using 2 different r/min test cycles and a ball-on-ring wear tester apparatus under boundary lubrication. The submicron powder mix was called fluorinated mixture with FeF3 catalyst to PTFE ratio of [1:2]. X-ray photoelectron spectroscopy and differential scanning calorimetry analysis of PTFE and FeF3 presented clear evidence of the catalyst importance in preparing the surface and lowering energy barrier. An explicit design of experiment analysis was developed to investigate the interactions of the fluorinated mix in commercial fully formulated oil and in plain oils subject to 2 different r/min test cycles of 100 r/min for the first 5000 revolutions and a 700 r/min until failure or 100 000 revolutions whichever comes first. All tests were generated under extreme boundary lubrication (Hertzian contact pressure of 2.72 GPa) and compared with 1 cycle at 700 r/min. The tests cylinders were baked in oil for a specific period of time and this was included as a factor in the 2-level factorial of the design of experiment (DOE). A fundamental and analytical study of the friction and wear performance was carried out on the plain zinc dialkyldithiophosphates (ZDDP) oil+(FeF3, PTFE) optimized DOE combination to justify the model predictions of the DOE. The fundamental analysis did not include commercial oils in the study since there were many components that affect the wear performance and frictional behaviour. Friction coefficient under boundary lubrication is affected by many factors. In order to study the friction characteristic of optimized tests, DOE was used to simplify experimentations and to investigate the failure and wear responses with respect to fluorinated mix interactions in plain and fully formulated oils. The 2 different r/min cycles tests indicate better performance than the one continuous 700 r/min cycle tests. Findings indicate that the positive factors affecting friction and wear are fluorinated mix concentrations together with oil formulations. Scanning electron microscopy, energy dispersive spectroscopy, focus ion beam, X-ray of wear track, and Auger electron spectroscopy were used to characterize the tribofilm of the two optimized tests of fluorinated mix in plain ZDDP oil under 1 continuous 700 r/min and 2 different r/min test cycles. Results indicate that the thickness of the tribofilms is in the range of 220 nm and phosphorus exists in both wear tracks with more traces in the 2 r/min cycles sample.