The effects of hardness on the spalling property of railway wheel steel

Spalling is a typical rolling contact fatigue (RCF) failure of locomotive wheels. The effects of hardness on the spalling properties of three wheel steels with different hardness levels were investigated. The RCF tests were conducted using two cylindrical contact specimens under water lubrication at a slip ratio of 1%. As a result, the fatigue strength and wear property increased with increasing hardness. The outer surface and cross section of the failure specimens were observed using optical and scanning electron microscopes. Cracks and obvious plastic deformation regions were observed under the contact surface. Both the depth of the main crack and crack branching increase rapidly with Hertzian stress. A model based on the Hirakawa failure model was proposed to describe the effects of hardness on the spalling behavior of wheel steels. With increasing hardness, the critical condition of the spalling increases, which agrees with the experimental results.