Print Email Facebook Twitter Stratified surface layers on rails Title Stratified surface layers on rails Author Messaadi, M. (TU Delft Railway Engineering) Steenbergen, M.J.M.M. (TU Delft Railway Engineering) Date 2018-11-15 Abstract This study examines the properties of stratified surface layers on rails in service and presents a hypothesis explaining their origin. The stratified layer consists of a white etching top layer and a brown sublayer. The metallurgical composition and properties of this sublayer are found to match with that of globular bainite. The occurrence of stratification in the surface layer is explained by the thermomechanical cycle for a material point on the rail surface under wheel-rail contact. Difference in the surface and subsurface cooling rates after reaching the austenitisation temperature may lead, depending on the chemical steel composition, to the generation of two different phases (martensite and bainite) and stratification. The exclusive occurrence of sandwich layers on rails that have been in service is attributed to the hardening of the top layer, leading to a reduced thermal conductivity, which gains relevance at an increasing depth. The granular morphology of the bainitic sublayer, exhibiting weak globular inclusions, facilitates the initiation and the propagation of transverse cracks, thus contributing to the development of RCF. Subject Brown etching layer (BEL)Granular bainiteRolling contact fatigue (RCF)Stratified surface layerThermomechanical cycleWhite etching layer (WEL) To reference this document use: http://resolver.tudelft.nl/uuid:75f4153f-a07a-4d73-bfa5-e9a47d154236 DOI https://doi.org/10.1016/j.wear.2018.07.019 Embargo date 2020-08-27 ISSN 0043-1648 Source Wear, 414-415, 151-162 Part of collection Institutional Repository Document type journal article Rights © 2018 M. Messaadi, M.J.M.M. Steenbergen Files PDF Paper_wear_stratification ... ersion.pdf 2.58 MB Close viewer /islandora/object/uuid:75f4153f-a07a-4d73-bfa5-e9a47d154236/datastream/OBJ/view