U76CrRE重轨钢的滚动接触疲劳/磨损复杂交互行为

Complex interaction behavior of rolling contact fatigue/wear of U76CrRE heavy rail steel

  • 摘要: 为了明确珠光体钢轨在滚动接触疲劳/磨损交互载荷下的伤损及表层微观组织演变规律. 本文以轧态、热处理态的珠光体重轨钢U76CrRE为研究对象,采用滚动摩擦磨损试验机、激光共聚焦显微镜(LSCM)、扫描电镜(SEM)、背散射衍射仪(EBSD)对无预制裂纹和有不同深度预制裂纹的钢轨磨损量、表面伤损、变形层、裂纹萌生及扩展进行测定和观察分析,结果表明,当无预制裂纹或预制裂纹深度小于磨损层时,轧态和热处理态钢轨均以磨损失效为主,但轧态钢轨的磨损量及变形层大于热处理态,其近变形层区域珠光体中的铁素体细化,与同样细化成小颗粒的渗碳体杂糅在一起,铁素体晶粒以小角度晶界为主,但随着距表层距离的增加,铁素体晶粒的大角度晶界比例逐渐增加,其裂纹呈现出角度大、深度深和长度小的特点,而热处理态钢轨的裂纹呈现出角度小、深度浅和长度大的特点,裂纹扩展趋势比轧态钢轨显著. 当预制裂纹深度大于磨损变形层时,预制裂纹会使钢轨提前结束磨损机制,促进疲劳裂纹的产生并迅速扩展,导致疲劳失效加快,裂纹呈现出角度大、深度深和长度大的扩展趋势,使得轧态和热处理态钢轨均以疲劳失效为主,其中轧态钢轨的裂纹扩展趋势比热处理态显著. 当轧态和热处理态钢轨在与硬度较高的车轮钢匹配时,裂纹角度、深度和长度都比与硬度较低的车轮钢匹配时显著.

     

    Abstract: Rolling contact fatigue and wear failure are the most common forms of failure in heavy rail steel. However, the complicated relationship between fatigue and wear of heavy rail steel remains largely unexplored, with the failure mechanism yet to be fully understood. To investigate the damage and surface microstructure evolution in pearlite rails under rolling contact fatigue and wear interactive loads, a study was conducted on U76CrRE pearlite heavy rail steel, both rolled and heat-treated. The research utilized various methods, including rolling friction and wear testing, laser confocal microscopy, scanning electron microscopy, and electron backscatter diffraction, to measure and observe the wear rate, surface damage, deformation layers, and crack initiation and propagation in heavy rail steel with and without precast cracks. The study quantitatively analyzed the microstructural evolution and failure behaviors of pearlite rail under wear and fatigue interaction loads. The results show that the deformation layer in rolled heavy rail steel is larger than that in heat-treated specimens, especially when there are no precast cracks or the depth of such cracks is less than the wear layer. However, the wear rate and deformation layer in rolled rails were found to exceed those in heat-treated rails. The ferrite in pearlite near the deformation layer is refined and mixed with similarly refined cementite particles. Initially, ferrite grains exhibit mainly small-angle grain boundaries, but as the distance from the surface layer increases, the proportion of large-angle grain boundaries grows, leading to cracks characterized by larger angles, greater depths, and shorter lengths. Conversely, cracks in heat-treated rails are characterized by smaller angles, shallower depths, and longer lengths, with a more pronounced trend of crack propagation compared to rolled rails. When prefabricated crack depth exceeds the wear deformation layer, these cracks expedite wear mechanisms, encouraging the rapid generation and propagation of fatigue cracks and hastening fatigue failure. The cracks tend to demonstrate larger angles, deeper depths, and longer lengths, indicating that both rolling and heat-treated pearlite heavy rails are mainly subject to fatigue failure, with crack propagation being more evident in rolled rails than in heat-treated ones. Furthermore, when rails are matched with wheel steel of higher hardness, the crack angle, depth and length of rails become more pronounced than those with lower hardness. Moreover, the duration of the rail wear mechanism is prolonged.

     

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