Effect of spherical dents on microstructure evolution and rolling contact fatigue of wheel/rail materials

Surface dents may occur on both rail head and wheel tread and have a deep influence on their microstructures. This investigation aims at exploring the microstructure evolution and RCF of wheel/rail materials with spherical dents. The experimental results, obtained through a suitable instrumented roller-rig, highlight the different microstructure evolutions not only between rail and wheel, but also between front and rear areas of dent. Electron backscattered diffraction data shows that the grains around dent on wheel have higher strain, mis-orientation and quantity of large angle grain boundaries than those on rail roller, leading to a weaker RCF resistance in wheel rollers. Meanwhile, cracks tend to propagate in front area of dent on rail and rear area of dent on wheel.