Study on Tensile and Compressive High-cycle Fatigue Crack Propagation Behavior of 590 MPa Grade Wheel Steel

In order to clarify the axial tension and compression high-cycle fatigue performance and fatigue fracture mechanism of 590 MPa grade wheel steel, the microstructure, fracture morphology and crack propagation behavior of the experimental steel were characterized and analyzed by optical microscopy, scanning electron microscopy, fracture nickel plating technique and EBSD. The results show that the fatigue strength of the experimental steel is 308 MPa; the fatigue crack initiates in the 90° angle zone on the surface of the specimen and carbide clusters, and the final fracture is caused by CaS inclusions after extension; the granular bainite, pearlite and M/A structure play an obstructive role in crack propagation,forming a tortuous propagation path represented by "Z" shape and causing secondary cracks. The orientation difference between adjacent grains near the fracture is very small, and it is easy to form straight crack; the angle of the active slip surface between adjacent grains is small, and the resistance of the crack to cross the grain boundary is small, forming a fatigue fracture dominated by transgranular extension.