Failure analysis of a crossing rail made of Hadfield steel after severe plastic deformation induced by wheel-rail interaction

In this study, the sub-surface structure of a railroad crossing made of Hadfield steel was characterized. The microhardness profile and metallographic examination, in addition to XRD, EBSD, and TEM analyses, were conducted on zones near the surface (damaged), where the rolling contact fatigue was operative. It was confirmed that mechanical twinning was the main deformation mechanism operative under these circumstances, through metallographic examination, Taylor analysis, misorientation profiles, TEM micrographs, and diffraction patterns. Further evidence suggested that near the affected surfaces, where superficial cracks were observed, nanotwins and small traces of epsilon (h.c.p) and alpha' (b.c.t) martensite were detected, in conjunction with dynamic recrystallization. This last phenomenon was verified due to the presence of very small grains located at the grain boundaries with random crystallographic orientation, the high local misorientation difference between the small grains and the large ones, and finally due to the appearance of the small annealing twins. These results are discussed based on the local misorientation, Schmid and Taylor analysis, twin types, and crystallographic orientation.