基于合金优化设计的动车组车轮钢高速滚动接触疲劳与磨损机理研究

Rolling contact fatigue and wear are the principal damages for EMU wheels. The main strengthening methods for EMU wheel steels include solution strengthening, precipitation strengthening and compound strengthening, all of which can be realized by alloy design. However, the influence mechanism of different strengthening methods on rolling contact fatigue and wear of EMU wheel steel is still unclear. In this project, rolling/sliding tests will be conducted for wheel steels that are respectively optimized by the strengthening methods stated above, where typical service conditions of EMU wheel are simulated. Considering the occurred condition of rolling contact fatigue and wear, wear resistance of wheel steel will be studied in dry condition, while rolling contact fatigue resistance of wheel steel will be studied in dry–wet condition. The tests at a linear speed of 5.65 km/h will be conducted to preliminarily determine the rolling contact fatigue and wear resistance of wheel steels. Then, the damage behavior of wheel steels in high-speed operation will be investigated at a linear speed of 250 km/h. After the test, the evolution of microstructure and property within the surface material will be analyzed. Then, the influence of microstructure and property evolution on rolling contact fatigue, wear and their competition will be investigated. Based on these studies, the influence mechanism of different strengthening methods on the damage behavior of EMU wheel steel in high-speed operation can be revealed. The findings from this project can provide a theoretical basis for determining the alloy design method to develop EMU wheel steels with better fatigue and wear resistance. They are also helpful to determine the material selection of high–speed EMU wheel according to the service conditions.

滚动接触疲劳和磨损是动车组车轮的主要损伤形式。通过合金优化设计以实现固溶强化、析出强化、固溶和析出复合强化是动车组车轮钢的主要强化机制。目前，不同强化机制对动车组车轮钢滚动接触疲劳和磨损的影响机理尚不清楚。本项目模拟典型的动车组车轮服役工况，对不同强化机制车轮钢进行滚动试验。根据疲劳和磨损发生的条件，在干态条件下研究磨损性能，在干态–水润滑条件下研究滚动接触疲劳性能。通过线速度5.65km/h的低速试验初步确定车轮钢滚动接触疲劳和磨损性能，然后通过线速度250km/h的高速试验进一步研究车轮钢在高速服役工况下的损伤行为。试验后，分析试样表层材料的组织和性能演变；阐明组织和性能演变对滚动接触疲劳、磨损和二者竞争关系的影响规律；揭示高速服役工况下强化机制对车轮钢损伤的影响机理。项目研究成果可为确定抗疲劳、抗磨损动车组车轮钢的合金化设计路线和不同服役工况下高速动车组车轮的选材方案提供理论支撑。

滚动接触疲劳和磨损是动车组车轮的主要损伤形式。针对服役工况、强化机制和缺陷对车轮钢滚动接触疲劳和磨损影响机理尚不清楚的问题，本项目开展了深入研究。通过试验和仿真分析了不同服役工况下车轮钢的滚动接触疲劳和磨损行为，建立了车轮钢磨损、裂纹萌生与扩展预测模型，阐明了服役工况对车轮钢疲劳和磨损的影响规律，提出了基于服役工况的动车组车轮选材方案，即低运行速度和低滑差率条件下，选用耐磨损车轮钢；低运行速度、高滑差率条件和高运行速度、低滑差率条件下，选用抗疲劳车轮钢；高运行速度和高滑差率条件下，车轮钢应兼具良好的疲劳和磨损性能。通过合金化设计和夹杂物改性对车轮钢进行强化，研究了不同强化机制车轮钢的微观组织、力学性能、疲劳与磨损性能；阐明了析出强化对车轮钢磨损性能的影响机理，发现析出强化可通过提高屈服强度改善车轮抗多边形磨损能力；建立了车轮热疲劳损伤仿真模型，分析了材料种类对热疲劳损伤的影响规律，发现固溶强化车轮钢在高温升速率下的相变温度明显高于普通车轮钢，因此具有良好的抗热疲劳损伤能力；通过试验和有限元仿真分析了夹杂物特征对疲劳裂纹扩展的影响规律，发现夹杂物塑性化处理后，硬质氧化物夹杂被软质硫化物包裹，夹杂物周围的镶嵌应力显著降低，车轮钢抗裂纹扩展能力提高。通过试验和仿真研究了含表面和内部缺陷车轮的滚动接触疲劳行为，建立了基于多轴疲劳模型和临界距离法的含表面缺陷车轮钢疲劳裂纹萌生模型，阐明了表面缺陷对接触疲劳损伤的影响机制，确定了诱发疲劳裂纹萌生的表面缺陷临界尺寸；通过本研究提出的缺陷疲劳评估法获得了轮辋内部缺陷的真实形状和尺寸，通过本研究提出的II型裂纹扩展试验方法获得了车轮钢II型裂纹扩展门槛值，在此基础上建立了辋裂裂纹萌生预测模型，确定了不同工况下引起动车组车轮辋裂裂纹萌生的内部缺陷临界尺寸。上述研究成果可为抗疲劳、耐磨损车轮钢的研制和动车组车轮的安全服役提供理论支撑。