EBSD study of early-damaging phenomena in wheel–rail model test

• Experimental modelling of rail-damage on lab-scale.
• Rail samples taken from real rail applications, equals real initial conditions.
• Identification of early damaging effects in ferritc–pearlitic microstructures.
• Quantification of microstructure modifications by EBSD.
• Development of model for damaging mechanisms for different contents of ferrite.

In the early-damage regime of rails subjected to rolling contact fatigue, the material undergoes severe plastic deformation forming a modified sub-surface microstructure. This zone close to the surface determines subsequent fatigue properties of the whole component and can differ considerably from an initial microstructure of the same material. Therefore, a fundamental understanding of early damage phenomena (<4000 cycles) is the focus of this work by comparing exemplary as a rolled standard R260 steel with a surface finished R260 pearlitic steel regarding their response to the rolling stresses by plastic deformation. Thus, electron backscatter diffraction technique based results were used to describe the material modification and set up a model for early-damage response of a pearlitic rail steel. Thereby, increased plastic deformation was found in the decarburized zone already after 100 cycles while the surface finished R260 remains almost undeformed. After 4000 cycles, both specimens have undergone high plastic deformation with work hardening concentrated directly below the surface for the decarburized steel and up to higher depths in the surface finished one.