Role of crystallographic orientation and grain boundaries in fatigue crack propagation in used pearlitic rail steel

The possible effects of crystallographic orientation and grain boundary distributions on fatigue crack initiation and propagation were studied in used pearlitic rail steels. Microstructure and hardness variation along the depth distance showed the effect of strain accumulation on microstructure modification. Although no evidence was shown of a correlation of inclusions and oxides with crack initiation, a high-pressure water environment entering into a crack can accelerate its propagation. Local crystallographic orientations analyzed closed to the crack path revealed that {110} grains oriented along the train passage plane, with a high Taylor factor and kernel average misorientation, are highly prone to crack propagation. This could be explained by the effect of local stress concentrations due to persistent slip bands.