【摘要】 重载列车频繁制动过程中，车轮踏面与闸瓦接触位置反复地快速加热和冷却产生的温度变化，会导致微观组织演变，可能造成开裂从而严重影响列车的安全运行。CL70是重载列车中普遍使用的车轮型号，其温度积累对裂纹、组织和性能稳定性的影响是应用服役中必须关注的问题。对CL70重载车轮进行了不同次数的冷热循环，研究了其在冷热循环下的损伤特性，并对显微组织演变进行了分析。结果表明：随着循环次数增加，CL70重载车轮在冷热循环下的开裂包括了裂纹萌生、扩展及合并长大阶段，表现出硬度衰减的现象，这一现象归因于珠光体和铁素体构成的基体组织的变化；在多次的冷热循环作用下，渗碳体发生球化，在铁素体片层相间结合处产生应力集中，萌生微裂纹，进而诱发并促进表面裂纹的扩展和软化行为。更多还原

【Abstract】 During the frequent braking process of heavy-duty trains, the temperature changes generated by the rapid heating and cooling of the contact position between the wheel tread and the brake shoe can lead to microstructural evolution, which may cause cracking and seriously affect the safe operation of the train. CL70 is a commonly used wheel in heavy-duty trains, and the effect of temperature accumulation on cracking, microstructure, and performance stability is a crucial issue that must be addressed during application and service. The CL70 heavy-duty wheel was subjected to different numbers of thermal cycling to study its damage characteristics under thermal cycles, and the microstructure evolution was analyzed. The results show that as the number of cycles increases, typical features such as crack initiation, propagation, coalescence, and growth become evident on the surface of the CL70 heavy-duty wheel after thermal cycling, which is attributed to changes in the matrix structure composed of pearlite and ferrite. During thermal cycling, the cementite undergoes spheroidization, resulting in stress concentration at the interface between ferrite lamellae, initiation of microcracks, and subsequent induction and promotion of surface crack propagation and softening behavior.更多还原