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U76CrRE重軌鋼的滾動接觸疲勞/磨損復雜交互行為

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

  • 摘要: 為了明確珠光體鋼軌在滾動接觸疲勞/磨損交互載荷下的傷損及表層微觀組織演變規律. 本文以軋態、熱處理態的珠光體重軌鋼U76CrRE為研究對象,采用滾動摩擦磨損試驗機、激光共聚焦顯微鏡(LSCM)、掃描電鏡(SEM)、背散射衍射儀(EBSD)對無預制裂紋和有不同深度預制裂紋的鋼軌磨損量、表面傷損、變形層、裂紋萌生及擴展進行測定和觀察分析,結果表明,當無預制裂紋或預制裂紋深度小于磨損層時,軋態和熱處理態鋼軌均以磨損失效為主,但軋態鋼軌的磨損量及變形層大于熱處理態,其近變形層區域珠光體中的鐵素體細化,與同樣細化成小顆粒的滲碳體雜糅在一起,鐵素體晶粒以小角度晶界為主,但隨著距表層距離的增加,鐵素體晶粒的大角度晶界比例逐漸增加,其裂紋呈現出角度大、深度深和長度小的特點,而熱處理態鋼軌的裂紋呈現出角度小、深度淺和長度大的特點,裂紋擴展趨勢比軋態鋼軌顯著. 當預制裂紋深度大于磨損變形層時,預制裂紋會使鋼軌提前結束磨損機制,促進疲勞裂紋的產生并迅速擴展,導致疲勞失效加快,裂紋呈現出角度大、深度深和長度大的擴展趨勢,使得軋態和熱處理態鋼軌均以疲勞失效為主,其中軋態鋼軌的裂紋擴展趨勢比熱處理態顯著. 當軋態和熱處理態鋼軌在與硬度較高的車輪鋼匹配時,裂紋角度、深度和長度都比與硬度較低的車輪鋼匹配時顯著.

     

    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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