Formation mechanism of brown etching layers in pearlitic rail steel

The formation of White Etching Layers (WELs) in rails can lead to the initiation microcracks, thus reducing service time rails. However, WEL mechanism is not yet understood. Brown (BELs) are intermediate microstructure located between parent pearlite and WEL. In this work, we use BELs as a microstructural tracer understand early stages formation. We study mechanisms an industrial R350HT rail steel retrieved from application. Atom probe tomography, complementary transmission electron microscopy, Kikuchi diffraction provide us access high resolution characterization. Carbon-depleted cementite lamellae sheared cut by dislocations. Several BEL areas with particles exist direct vicinity pearlite. Energy dispersive X-ray spectroscopy reveals redistribution carbon inhomogeneous distribution manganese areas. These results suggest correlation decomposition BEL. Deformation-induced causes local alterations regarding defect density composition, leading austenite aided temperature ingress during rail/wheel contacts.