A Newly Developed Heavy-Haul Wheel Steel with Excellent Rolling Contact Fatigue Performance Assessed by an Innovative Vision System

As railway transportation advances towards higher speeds and increased axle loads, the fatigue damage between wheels and rails has become more severe, significantly limiting the service life and safety of trains. Therefore, developing upgrade wheel-rail materials with enhanced contact fatigue properties has been considered an effective approach to avoid damage. This study reports a newly developed heavy-haul wheel steel with a superior rolling contact fatigue performance and the fatigue damage of wheel was studied by a novel RCF tester with a vision system. The results indicate that the newly developed heavy-haul wheel steel (NW) consists of smaller pearlite layer spacing and reduced proeutectoid ferrite. The NW steel demonstrates outstanding fatigue resistance in both oil and dry conditions, with a fatigue life 2.7 times longer than CL65 wheel steel and superior performance compared to most typical wheel steels. With increasing in pearlite content and decreasing in pearlitic interlamellar spacing, the fatigue damage degree of wheels under oil or dry contact conditions decreases obviously, leading to a significant enhancement in fatigue life. Properly controlling the pearlite content and the interlamellar spacing can optimize the fatigue properties of wheel materials. The vision system observed that the average area and perimeter of the defects gradually increased on the sample surface. The shape of the defect became more rounded under oil contact conditions but showed the opposite result in dry contact. When subjected to cyclic loading, surface cracks propagated along various paths after initiation, eventually forming different morphologies of peeling. The results will not only help optimize wheel materials for heavy-haul railways, but also offer an effective means for analyzing damage evolution in wheel-rail contact.