Effective Approach to Mitigating Rolling Contact Damage in Railway Rails: Utilizing Cryogenic Treatment and Process Optimization

In order to reduce the failure behaviors of rail steels, special heat treatment has been investigated as an efficient method to modify the matrix microstructure and improve material performance. In this study, the effect of the process sequence of cryogenic treatment on microstructure characteristics and rolling damage resistance was investigated on the basis of quenching-tempering (QT), quenching-cryogenic treatment-tempering (QCT), and quenching-tempering-cryogenic treatment (QTC). The study results indicated that the introduction of cryogenic treatment effectively promoted the transformation of residual austenite to martensite and increased the dislocation density. Besides, cryogenic treatment before tempering could refine the carbides and reduce the width of martensite laths to enhance the matrix strength and hardness. Meanwhile, the fine carbides, high dislocation density and low residual austenite content effectively resisted plastic deformation and the movement of the crystal slip system during rolling contact. Consequently, wear loss and the thickness of the plastic deformation layer reduced by 20.6% and 59.7%, and surface spalling and fatigue cracking were mitigated compared to QT samples. Additionally, cryogenic treatment enhanced the adhesion coefficient during rolling contact due to microstructure modification. In summary, cryogenic treatment before tempering was more beneficial in improving rolling damage resistance of rail steels.