Micropitting and microstructural evolution during gear testing -from initial cycles to failure. (April 2021)

• Record Type: Journal Article
• Authors: Mallipeddi, D.; Norell, M.; Naidu, V.M. Subbaramaiah; Zhang, X.; Näslund, M.; Nyborg, L.
• Is Part Of: Tribology international. Volume 156(2021)
• Publication Date: 2021-04
• Subjects: Tribology -- Periodicals; 621.89
• DOI: 10.1016/j.triboint.2020.106820
• Languages: English
• ISSNs: 0301-679X

Abstract

Abstract: To elucidate the micropitting mechanism, ground gears were tested using FZG test rig and the evolution of surface characteristics were followed closely from the initial 200 cycles to failure. Micropitting phenomenon was divided into three stages; running-in, steady progression and degradation. Micropitting was mainly associated with plastic deformation of asperities, which induced localized deformation bands and plastically deformed regions that were associated with cracks. Build-up of residual stresses occurred during running-in and this was correlated to the transformation of retained austenite. No further evolution occurred during steady progression stage and then the stresses decreased during degradation stage. Phosphorus content in the gear surface increased during steady progression stage and remained similar during degradation stage but with increased layer thickness. Highlights: Micropitting phenomenon was divided into three stages; running-in, steady progression and degradation. Micropitting was mainly associated with plastic deformation of asperities, which induced localized deformation bands. Micropits initiated around 2000 cycles, progressed further and developed into macro-pits at around 2.2 x 10 7 cycles. Build-up of residual stresses occurred during running-in and this was correlated to transformation of retained austenite. Phosphorus content increased during steady progression and remained similar during degradation stage but with increased layer thickness.