Severe Plastic Deformed Zones and White Etching Layers Formed During Service of Railway Wheels

Abstract

The near-surface regions of rail wheels experience a complex thermo-mechanical loading, which varies along the location of the tread and causes severe changes to the microstructure. Occasionally, brittle white etching layers (WEL) are formed, representing a high risk of wheel damage. Therefore, we studied the depth-evolution of the surface-near microstructure along different regions of the tread of a wheel being ~ 200,000 km in service. The microstructural variations point toward a higher thermal loading history in the middle of the tread and predominant mechanical loading in the neighboring regions, where a severe plastic deformed microstructure with rolling contact fatigue cracks is present. Varieties of WEL-like microstructures were investigated, the presented analysis contributes to the knowledge of their microstructural characteristics and outpoints these regions in terms of potential crack initiation sites on railway wheels.