Microstructural changes in the gauge corner for heavy haul pearlitic rails with and without lubrication

Abstract

This study examines microstructural changes in heavy-haul pearlitic rails under lubricated and unlubricated conditions at the gauge corner, focusing on wear mechanisms and crack nucleation. Samples from curved tracks with radii of 343 m (S1) and 570 m (S2) were analyzed using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and nano-hardness profiling. S1, lubricated with grease, showed a reduced coefficient of friction (CoF = 0.21 ± 0.04), mitigating wear and shifting the damage regime to elastic and high-cycle fatigue zones. In contrast, S2, unlubricated, exhibited a higher CoF (0.45 ± 0.03), increased plastic deformation, and crack propagation consistent with rolling contact fatigue (RCF). Both samples exhibited White Etching Layers (WEL) and Transitional Layers (TL/BEL), with thicker layers and more pronounced damage in S2. Hardness profiling revealed elevated values (up to 14 GPa) in WEL regions, driven by thermal and mechanical effects. While hardening reduced material removal, it exacerbated surface crack nucleation, particularly in high curvature areas. These results underscore the critical role of lubrication in reducing wear, delaying rail replacement, and optimizing maintenance strategies. A shakedown diagram further illustrates the operational influences on wear mechanisms, providing insights into enhancing the performance and longevity of heavy-haul rail systems.