Microstructural characterisation of rolling contact fatigue damage in flashbutt welds

Gauge corner cracking was found to initiate in the softened zone associated with spheroidised microstructure. The role of pro-eutectoid cementite network on crack initiation was difficult to evaluate, however, it seems to have only a minor effect on crack propagation. The proposed options to mitigate gauge corner cracking was to make narrow welds to minimise softened zone or to select rail grades that are more resistant to spheroidisation.