Comparative study on wear and fatigue behaviors of rail steels with varying levels of martensite and bainite under rolling-sliding contact conditions

Abstract

With increasing axle loads and train speeds, pearlitic rail steels are subjected to significant challenges in this service condition due to its wear resistance and hardness limitation. In this paper, the rail steel with different martensite and bainite contents is prepared by isothermal quenching. The effect of these microstructural changes on rolling contact damage behaviors was investigated using dry-wet contact wear tests. The results indicate that the rail steel is primarily composed of bainite and martensite after isothermal quenching. Compared to the pearlitic microstructure before isothermal quenching, the mixed martensite and bainite microstructure of rail steel achieved by isothermal quenching effectively mitigates rolling contact damage and resists plastic deformation. This improvement is associated with increased material hardness, reduced grain angles and grain refinement. Meanwhile, the plastic deformation zone caused by rolling contact presents a hardening phenomenon, accompanied by increased dislocation density and grain refinement. This hardening layer effectively hinders crack propagation to greater depths. In addition, due to the intense splitting of austenite grains by martensite during quenching, rail steels with high martensite contents possessed high material hardness and small grain size. Therefore, under rolling contact wear, it was found that fatigue cracking without matrix spalling was the primary wear behavior on the wear surface of rail steel with high martensite contents, and its crack length was reduced by 30.8 % compared to pearlitic microstructure.