Characterisation of plastic deformation and thermal softening of the surface layer of railway passenger wheel treads

Microstructure, plastic deformation and annealing properties of the material in the outermost tread layer of used passenger railway wheels were characterised. Large deformation existed up to 5 mm depth below the surface and material flow, i.e. shear strain, was present both in tangential- and transverse directions of the wheel. Close to the field side and flange root moderate rolling contact fatigue was observed, where also the largest work hardening and shear deformation were measured. Annealing trials at temperatures around 500 °C showed softening of the deformed surface layer at lower temperatures and at higher rate than for non-deformed material.