Multi-axial Fatigue of Head-Hardened Pearlitic and Austenitic Manganese Railway Steels: A Comparative Study

Switches and crossings (S&Cs) in rail networks suffer from damage and deformation due to severe loading of their complex geometric shapes. This article presents a comparative study of the cyclic deformation characteristics and fatigue behavior of two typical crossing materials, namely head-hardened pearlitic steel and Hadfield manganese steel, as well as the associated microstructural changes. Both uniaxial and biaxial loadings (proportional and non-proportional) are studied. The pearlitic steel endured more cycles to failure for a given strain amplitude compared to the manganese steel. The cyclic response of manganese steel shows significant hardening whereas softening was observed for the pearlitic steel except under biaxial non-proportional loading. The microstructures developed in the two types of steels after deformation are characterized by optical (OM) and transmission electron microscopy (TEM). TEM micrographs reveal that the deformed microstructure of the pearlitic steel consists of threading dislocations and dislocation tangles in the ferrite lamellae. The microstructures in the manganese steel after the different loadings are composed of dislocation cells with dislocation tangles inside, intersected by straight stacking fault lamellae. The observed microstructures are related to the results of the mechanical test, and the suitability of the steels for use in S&Cs is discussed.