White etching layers on the Stockholm local traffic network

Paper i proceeding, 2012

Top layers of railway rails are subjected to microstructural changes sometimes resulting in white etching layers. These thin layers are more brittle than the base material and show increased cracking and spalling. For the present study pearlitic rail samples from curves without corrugation from the Stockholm local traffic network (SL) have been investigated concerning their influence on the crack initiation and crack propagation into the base material. Samples with white etching layers were subjected to tensile loads. The white etching layers and crack surfaces were examined with light and scanning electron microscope. White etching layers with a thickness of 200µm were found. It can be concluded that they consist mostly of martensite with a hardness two to three times higher than the base material. Cracks growing through the white etching layer initiating cracks in the pearlite have been found. Also, the crack sensitivity is higher for the white etching layer as compared to the base material and it creates initiation points for cracks in the pearlitic part of the rail.