U75VG钢轨钢相变白层在摩擦磨损过程中表面组织和性能的变化

    Change of Microstructure and Properties of Surface of U75VG Rail Steel Phase Transition White Layer During Friction and Wear

    • 摘要: 对U75VG钢轨钢试样表面进行局部激光淬火,在试样表面获得具有条带状的马氏体相变白层,U75VG钢轨钢淬火前后两种试样与配试样车轮钢ER8C对磨,在GPM-40滚动接触摩擦疲劳实验机进行滚动磨损实验。采用硬度计、精密电子天平、扫描电镜等分析相变白层在摩擦磨损过程中表面的组织和性能。结果表明:U75VG钢轨钢激光淬火处理试样在磨损实验运行时,易在激光淬火相变白层条带的起始端、终止端和两侧表面萌生裂纹,裂纹易在相变白层边缘与基体交界面及白层内扩展。没有相变白层条带的部位和原始试样磨损形貌一样,损伤均匀。在磨损实验运行70万转时,根据失重,U75VG钢轨钢激光淬火处理试样相对于U75VG钢轨钢原始试样磨损性能好,但U75VG钢轨钢淬火试样存在相变白层边缘与基体交界面易萌生裂纹、裂纹扩展和剥落等缺陷。

       

      Abstract: The surface of U75VG rail steel sample was subjected to local laser quenching, and the banded white layer with martensite transformation was obtained on the surface of the sample. Before and after quenching, two kinds of rail steel samples were grand against the accompanying wheel steel ER8C, and the rolling wear test was carried out on GPM-40 rolling contact friction fatigue testing machine. The microstructure and properties of of the surface of phase transition white layer during friction wear were analyzed by means of hardness tester, precision electronic balance and scanning electron microscope. The results show that during the wear test of U75VG rail steel samples treated by laser quenching, cracks are easy to generate at the starting end, ending end and both sides of the laser quenching phase change white layer strip, and the cracks are easy to expand at the interface between the edge of phase change white layer and the matrix and inside the white layer. The wear morphology of the strip without phase change white layer is the same as that of the original specimen, and the damage is uniform. When the wear test is run at 700000 turns, according to the mass loss, the laser quenched sample of U75VG rail steel has better wear performance than that of the original sample of U75VG rail steel. However, the quenched sample of U75VG rail steel is prone to crack initiation, crack propagation and spalling at the interface between the edge of phase-change white layer and the matrix, which is locally vulnerable to damage.

       

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