Abstract
In order to clarify the influence of environmental humidity (RH = 10-70 %) on the fretting characteristics of steels under grease lubrication an experimental investigation is performed. Ball (bearing steel) on disk (carbon steel) type fretting tests for 0-20 mg of grease supplied before each test at the punctual contact between ball and disk were conducted at 50 μm slip amplitude and 6.7 Hz frequency. From the shape of the friction hysteresis one calculates the slip index, and based on it, determines the type of fretting regime against the number of fretting cycles. Influence of the grease amount and relative humidity on the friction coefficient, wear rate and slip index is interpreted based on the occurrence of the grease film breakdown. Such results are useful to find the amount of grease necessary but sufficient for proper lubrication, and hence to protect the environment by grease saving.
