Dry Rolling/Sliding Wear of Bainitic Rail Steels under Different Contact Stresses and Slip Ratios.

Yue Hu,Tong Shi,Yinhua Zhang,Haohao Ding,Shaobo Zhou,Fengshou Liu,Lubing Shi,Jiapeng Liu,Wenjian Wang,Yingqi Li

doi:10.3390/ma13204678

Yue Hu, Tong Shi + Show 8 more

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https://doi.org/10.3390/ma13204678

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Abstract

This study aims to deeply understand the effect of contact stress and slip ratio on wear performances of bainitic rail steels. The results showed that the wear loss increased as the contact stress and slip ratio increased. Based on the surface damage morphology and microstructural analyses, it revealed that the rolling contact fatigue wear mechanism played a significant role under the low slip ratio, but the dominant wear mechanism transferred to the abrasive wear at the high slip ratio. Meanwhile, the bainitic steel specifically presented worse wear resistance under the abrasive wear mode. Compared with the influence of a slip ratio, the increase in contact stress led to severer plastic flows and contributed to the propagation of cracks. In addition, the contact stress and slip ratio had the opposite effect on the friction coefficient, that is, the friction coefficient of bainitic steels behaved the inverse proportion with the contact stress, but positive proportion with the slip ratio. At last, the increase in slip ratio had more significant effect on the reduction of retained austenite (RA) than the enlargement of contact stress due to the fact that the RA would probably be removed before the martensitic transformation occurred under the abrasive wear mechanism.

Highlights

Pearlitic steel has been widely used in railway system, but the conventional pearlitic steel is susceptible to the formation of various defects, such as head checks and corrugation under actual rail-wheel contact conditions, which may lead to rail fracture and consume a great deal of maintenance cost and time [1,2,3]
The wear state gradually transferred from the running-in period to the stable status, where the friction torque turned to be stable after 15 k rolling cycles
The wear loss increases with the rise of the contact stress and slip ratio, but the slip ratio plays a more crucial role on aggravating wear loss than the contact stress

Summary

Introduction

Pearlitic steel has been widely used in railway system, but the conventional pearlitic steel is susceptible to the formation of various defects, such as head checks and corrugation under actual rail-wheel contact conditions, which may lead to rail fracture and consume a great deal of maintenance cost and time [1,2,3]. Without regard to the welding limit, continuously cooled carbide-free bainitic steel is a kind of potential candidate for railway applications owing to its higher fracture toughness and fatigue resistance [2,3,4]. It has been reported that the thickness of bainitic lath can achieve to the nanometer level by the isothermal heat treatment [4,5,6]. These bainitic steels perform better mechanical properties than continuous cooling bainitic steels. In our study, we focus on the continuous cooling carbide-free bainitic rail which was produced from the real rail manufacture

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