A common surface metallurgical feature of rail is white etching layer (WEL), a martensitic structure formed due to severe deformation of rail while it is in service. The simulation of white etching layer has involved sliding one disc against another to produce the WEL by deformation. Rolling contact fatigue (RCF) of this layer has been investigated in the laboratory using twin-disc testing. The effect of the white etching layer is to reduce the resistance of rail steel to crack initiation because of its brittle nature, with propagation promoted by the continued deformation of the sub-surface pearlite. Rails removed from service have been examined and compared with the twin disc testing samples. RCF cracks initiate at the interface of the WEL and pearlite due to the ductility difference between them.

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