Investigation on WEA fatigue spalling of U71MnG rail material subject to laser quenching surface treatment

In this study, the fatigue spalling process and mechanism of the white etched area (WEA) caused by the laser quenching surface treatment of U71MnG rail material were investigated. The results demonstrate that the surface pearlite is visibly deformed under normal stress and creep force during the initial wear stage, whereas the WEA is not deformed. Discordant plastic deformation results in the formation of cracks at the contact between the initial position of the WEA and the substrate, which then propagates into the WEA. As the number of rolling cycles increases, the formation and propagation of cracks gradually shift into the middle of the WEA and branch cracks form, which eventually intersect and cause spalling. The substrate's plastic flow covers the WEA terminal po-sition surface; the WEA edge fracture is formed due to bending under normal stress. Plastic deformation enhances the surface hardness of WEA. The substrate's apparent plastic deformation beneath the WEA suggests that the WEA flows under the influence of creep forces.

Automated summary

This study investigates the fatigue spalling process and mechanism of the white etched area (WEA) caused by laser quenching surface treatment of U71MnG rail material. The results show that the surface pearlite deforms under normal stress and creep force during the initial wear stage, while the WEA remains unaffected. Cracks form at the contact between the initial position of the WEA and the substrate due to discordant plastic deformation, which then propagate into the WEA. With increasing rolling cycles, cracks gradually shift into the middle of the WEA, form branch cracks, and eventually intersect, resulting in spalling. The plastic flow of the substrate covers the WEA surface at the terminal position, and WEA edge fracture occurs due to bending under normal stress. Plastic deformation enhances the surface hardness of the WEA, and the apparent plastic deformation of the substrate beneath the WEA suggests that the WEA flows under the influence of creep forces.