Fretting and mechanically-assisted crevice corrosion (MACC) of rail steel U75V with PA66 liner

Abstract

Strong evidence has been reported on the occurrence of mechanically-assisted crevice corrosion (MACC) between the upper surface of the rail foot and the liner of the fastener, but there is still a lack of attention regarding its effect on materials degradation. A novel testing apparatus was self-developed in this study to simulate the MACC between the rail foot and the liner (disc-on-disc), and a typical rail steel (U75V) and a typical material for the liner (PA66) have been utilized. The fretting regimes, electrochemical behaviors and morphology of the contact surface have been investigated. It has been found that the fretting was mainly controlled by partial slip regime under the condition in this study, and the OCP and anodic current were both increased with increasing fretting frequency and displacement amplitude. The presence of PA66 debris in the form of large spalling particles has been found to inhibit crevice corrosion and relieve the surface damage to some extent. Cracks and local surface collapse were typically noticed on U75V steel which have been ascribed to the accumulation of plastic deformation and the comprehensive effect of fretting wear and corrosion fatigue.