On the Relationship between Micropitting and Friction/Wear of Rolling-Sliding Steel/Steel Contacts

Abstract

Micropitting phenomenon has been extensively studied in previous studies while the mechanism of micropitting formation process with relationship to friction and wear performance is scarcely researched. In this paper, two commercial lubricants were tested in a micropitting rig at different slide to roll ratios and relative humidities to evaluate the relationship between tribological performance and micropitting level. An optical microscope was applied to obtain the micropitting level on the contacting surface after tribological tests. The results showed higher relative humidity and slide to roll ratio always leaded to higher wear, while the friction change did not have a universe trend. The micropitting level was a combined effect of friction and wear. To explain this complex phenomenon, two mechanisms of the relationship between wear and micropitting performance were introduced. The two mechanisms were highly related to the propagation speed of micropits formed from small etching cracks and the removal speed of micropits due to wear. The outcome of this paper is beneficial to the evaluation of the performance of lubricants applied in rolling-sliding contacts.