Keywords: Hadfield manganese steel, swing-nose crossing, fixed crossing, work hardening, rolling contact fatigue, impact load, wheel-rail contact.

This study compares damage mechanisms in fixed and swing-nose crossings made of Hadfield manganese steel used in high-speed rail, with particular focus on the influence of impact loading on deformation behavior and crack morphology. Although Hadfield steel exhibits high work-hardening capacity, repeated wheel loading leads to progressive surface hardening and eventual fatigue crack initiation. Specimens extracted from in-service crossings were experimentally analyzed. In the swing-nose crossing, rolling contact-induced shear stress was dominant. Work hardening extended to a depth of approximately 3 mm, and surface-parallel cracks, similar to rail squats, were observed. In contrast, the fixed crossing experienced significant impact loading during wheel transfer, resulting in higher surface hardness (up to 650 HV) and a deeper work-hardened layer exceeding 5 mm. In addition to surface-parallel cracks, vertical and internal horizontal cracks were identified. Twinning deformation under impact loading was concentrated in a preferred direction, corresponding to crack propagation paths. X-ray diffraction revealed peak broadening near the surface in both crossings, with more pronounced broadening in the fixed crossing, indicating higher strain. These results demonstrate that impact loading strongly affects strain distribution, work-hardening depth, and crack configuration.

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