Effect of Rolling Direction on Contact Fatigue Damage of CL60 Wheel Steel

In order to investigate the effect of wheel rolling direction on rolling contact fatigue (RCF) damage of wheel steel, the rolling-sliding wear experiments under both unidirectional and bidirectional conditions were carried out on a rolling wear testing apparatus (WR-1, China). The wheel surface damage, section fatigue crack morphology and wear debris size were observed by optical microscope and scanning electron microscope, the evolution law of wheel surface damage, fatigue crack propagation and debris size with the number of reverse cycles under reversing operating conditions were investigated. The results show that the wheel surface damage is mainly caused by peeling. As the number of reverse cycles increases from 10 000 to 120 000, the initial peelings gradually wear off and then new peelings are formed opposite to the original rolling direction, changing wheel rolling direction is beneficial to reduce the RCF damage of wheel materials under the same test cycles. The propagation direction of surface microcracks is changed after wheel reverse rolling, forming reverse fatigue cracks of 4°−8°, and crack distortion and branching occur on the wheel samples. As the number of cycles increases, the debris size increases firstly and then decreases under unidirectional condition, after wheel reverse rolling, the debris thickness increases firstly and then decreases, the thickness increases to 10−12 μm after reversing 10 000 cycles, which is twice as much as under the unidirectional condition.