Wear and Rolling Contact Fatigue Behavior of Pearlitic and Bainitic Rail Steels under Different Operating Parameters

Objective Rail service plays a crucial role in facilitating train support, guidance, and high-speed operation, constituting a core component of track structure. It directly impacts the operational safety of high-speed railway trains. Wear and rolling contact fatigue (RCF) are the primary mechanisms causing damage to rail materials during wheel-rail service processes. To investigate the influence of rail material and operational conditions on rail wear and RCF behavior, twin-disc rolling-sliding tests were conducted. Method In the present study, hypoeutectoid, eutectoid and bainitic rail steels were selected to run against CL60 wheel. Seven series of tests were conducted, and each tests were all running for 500 000 cycles. Tests were performed under three wheel velocities (120, 200 and 250 r/min), three axle loads (17, 21 and 25t) and three curvature radius (flat, 600 and 2000 m). The wear and RCF behavior of rail materials after the test were analyzed in details. Results The results indicated that the wear rate of eutectoid rail material was always higher than that of hypoeutectoid rail and bainite rail. The surface damage of eutectoid rail materials was always more severe than the other two materials. The surface damage of bainite steel rail material was the least severe, with only a number of pits distributed and almost no material peelings. The plastic deformation layer depth of eutectoid steel rail was about 1.8 times that of hypoeutectoid steel rail and bainite steel rail materials. The crack length and depth of pearlite rail materials were generally greater than those of bainite rail materials. With the velocity increased, the wear rate and surface damage degree of the rail material generally showed a decreasing trend. And there was almost no effect on the depth of plastic deformation layer and the degree of crack damage of rail materials. With the axle load increased, the surface damage and plastic deformation layer depth of the three rail materials gradually increased. And the degree of RCF crack damage would gradually intensify under the increasing wheel-rail contact effect with the axle load increases. When the axle load further increased to 25 t, material peeling would occur on the rail surface, which would reduce the length and depth of the cracks. Reducing the curvature radius would lead to an increase in the lateral force, thereby increasing the wear rate and plastic deformation layer depth of the rail material. As the curvature radius decreased, the rail surface damage significantly intensified, especially for pearlite materials with a 600 m curve radius, there were a large number of layered material peelings on the surface. Conclusions Under identical operational conditions, variations in wear and RCF behavior were observed among different rail materials. Generally, bainitic steel rail materials exhibited milder damage compared to eutectoid steel rails. As velocity increased, the wear rate of rail material decreased, along with a reduction in surface damage. Conversely, with increased axle load, both the material wear rate and the depth of plastic deformation layer increased, resulting in heightened surface damage. Additionally, fatigue crack damage initially increased and then diminished. Notably, the trends of material wear rate, plastic deformation layer depth, and surface damage degree showed a negative correlation with curvature radius. Rail material sustained more severe damage under operating conditions characterized by lower speeds, heavier axle loads, and smaller curvature radii on railway lines. Consequently, timely implementation of corresponding repair measures was imperative.