Crystal orientation analysis of running surface of rail damaged by rolling contact

The crystal orientation in the surface layer of a rail was analyzed by means of X-ray inverse pole figure measurement, electron back scattering pattern (EBSP) analysis and transmission electron microscope (TEM) observation for the rail used in service on a narrow-gauge line for 16 years with an accumulated service tonnage of 160 MGT and damaged by repeated rolling contact with wheels of rolling stock. The specific condition that the {1 1 1} crystallographic plane of the constituent grains is oriented parallel to the running surface in the surface layer of the rail is confirmed through the analysis of X-ray inverse pole figure and EBSP orientation image map. The degree of orientation evaluated by the axis density of the 1 1 1 crystallographic axis varies in the direction of depth from the running surface giving a maximum at about 100 μm from the surface. Based on these results, the 1 1 1 axis density is thought to be a potential parameter to evaluate the degree of the rolling contact damage accumulated in the surface layer of rails used in service.