Understanding microstructure-evolution-dependent fracture behaviors in pearlitic steels

Abstract

Microstructure evolution or degradation has been well recognized to be closely related to the formation of microcracks in pearlitic rails and wheels. The rolling contact fatigue machine was employed to simulate the rail–wheel contact, and the microstructure evolution and crack formation of pearlitic steels subjected to rolling–sliding contact loading were then experimentally characterized. To further quantitatively predict the fracture behaviors, a phase-field model was herein established to investigate the cyclic loading-driven microstructure evolution and the microstructure-dependent fracture resistance in pearlite. The coupling of microstructure evolution and crack propagation was realized through the introduction of two-set order parameters, i.e., the crack field and the microstructure field, and the microstructure-dependent fracture toughness. The proposed model can predict the fracture resistance of microstructure at different depths from the contact surface, after different rolling cycles and with different initial pearlitic microstructures, which can shed light on the design of damage-resistant microstructure of pearlitic steels.