Experimental investigation on the effect of operating speeds on wear and rolling contact fatigue damage of wheel materials

Abstract

The objective of this study is to explore the wear and rolling contact fatigue (RCF) characteristics of wheel materials under different operating speeds conditions using a small scale wheel/rail facility. The results indicate that the operating speed plays a vital role in the wear and RCF of wheel materials. As the operating speed increases, both the surface hardness and the hardness of the plastic flow layer on the wheel roller decrease while the worn surfaces become rougher. Shear strain hardening of wheel roller decreases with increasing operating speed. Furthermore, the primary damage mechanism of the wheel roller transforms from spalling and slight surface fatigue to severe fatigue cracks as the operating speed increases. Fatigue cracks initiate from the wear surface and grow along with the soft ferrite lines within the plastically deformation layer. RCF damage become more severe and the wear rate of the wheel roller decreases as operating speed increases. Low wear rate can not adequately remove cracks and leads to a visible increase in the angle of fatigue crack propagation and the crack depth. Furthermore, the wear debris is composed of metallic flakes whose primary compositions are iron, Fe2O3, and Fe3O4 and the size of wear debris decreases, but the thickness increases as operating speed increases.