Influence of oil formulation on gear micropitting and power loss performance

Abstract

This study presents a study of the influence of oil formulation on the protection against gear micropitting and also its influence on gear efficiency. The study had both components because a well-balanced product is necessary and its behaviour must be demonstrated in dedicated tests. The industrial gear oils studied combined polyalphaolefin with ester base oils and had different additive packages. FZG gear power loss tests were performed using 20MnCr5 carburized gears under a wide range of operating conditions. During the tests, the oil and gearbox temperature were continuously recorded and gear oil samples were collected. After the tests, the gear mass loss was measured and oil samples were analyzed by ferrography. Using an energetic model of the FZG test gearbox, it was possible to quantify the influence of lubricant formulation on the average friction coefficient between gear teeth, which will provide a quantitative comparison of lubricants. The gear micropitting protection provided by the oxidized lubricant samples was evaluated in a FZG test rig according to DGMK short micropitting test procedure. During the tests, lubricant analysis, mass loss measurements, surface observation, and topography measurements were performed to evaluate the micropitting evolution along the tests as well as severity of micropitting. The results obtained show that the base oil, the additive package, as well as their combination can have a very significant influence on the efficiency and micropitting performance of industrial gear oil.

Keywords

gears micropitting power losses friction coefficient lubricants

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