Influence of white layer geometry and material strength on spalling properties in railway wheel steels

Spalling is one of the typical failures of railway wheels. Spalling is rolling contact fatigue (RCF) damages, as the result of unexpected wheel slides on the rail. One of the major characteristics of spalling is that a part of the wheel surface transforms to white layers by a frictional heat of the slides. In this study, in order to evaluate the influence of white layer geometries and material strengths on the spalling properties of the wheel steels, RCF tests and elasticplastic FEM analyses were carried out. Moreover, the Dang Van model, which is one of the multiaxial fatigue strength evaluation methods, was applied to predict the white layer's fatigue strength in RCF tests. There are three main results from this study. Firstly, RCF tests yielded that the crack initiations were less in the smaller white layers than in the larger ones. In addition, the crack initiations from the white layers were less in the higher strength of the matrix than in the lower strength of it. Secondly, FEM analysis results showed that the maximum stresses were lower in the smaller white layers than in the larger ones. The maximum stresses of the white layers also were lower in the higher strength of the matrix than in the lower strength of it. These results corresponded to the crack initiation behaviors of RCF tests. Finally, the fatigue strength prediction results by the Dang Van model were reasonably equivalent to the spalling properties obtained by RCF tests. Therefore it was concluded that the white layer geometries and the strength of the matrix much influenced the spalling properties, and these results were predicted by the fatigue strength evaluation method that we proposed. © 2009 The Society of Materials Science, Japan.