A study of rolling contact fatigue crack growth in U75V and U71Mn rails

Rolling contact fatigue (RCF) failure is a permanent and quite severe problem and hence of major concern to the modern railway industry. The selection of rail material should be based on a well-founded understanding of RCF. An analysis of the chemical composition, mechanical performance and microstructure was performed on U75V and U71Mn rail samples with oblique cracks taken from Guangzhou–Shenzhen railway. The results indicate that the strength character of U75V rail is superior to U71Mn rail. The crack propagation angle to the surface of U71Mn rail is smaller than that of U75V rail. A mixture of intergranular and transgranular fracture was found dominant in the process of fatigue crack propagation of U71Mn rail; in comparison, the dominant fracture mode of U75V rail is transgranular and the crack is easier to propagate at a relatively higher rate. The analysis shows that U71Mn rail is more suitable for the high-speed railway.