不同钢轨材料的风沙冲蚀磨损与损伤行为研究

随着铁路的快速发展，风沙地区的铁路线路分布越来越广，在本文中采用气流喷砂式冲蚀试验机以天然混合沙对不同钢轨材料的风沙冲蚀磨损与损伤行为进行了研究. 结果表明:钢轨材料的冲蚀率随着冲蚀角度的增加先增加后减少；最大冲蚀率出现在30°~45°之间；抗风沙冲蚀磨损性能依次为热处理过共析钢轨>热处理U78CrV>热轧U71Mn>热处理U75V>热轧U75V；延性对热轧钢轨材料的抗冲蚀磨损性能的影响大于硬度，而硬度对热处理钢轨材料的影响大于延性，在线热处理可以提高U75V钢轨的抗冲蚀磨损性能；钢轨材料冲蚀损伤的主要特征为片屑、蚀坑、塑性流动及裂纹；钢轨材料在风沙冲蚀下展现出延性冲蚀模式，其材料去除机制主要为成片机制. 

Windblown Sand Erosion Wear and Damage Behaviors of Different Rail Steels

Objective With the rapid development of railway transportation, more railways were constructed in the windblown sand areas. As the railways serve in an open environment, the rails in the windblown sand areas are inevitably eroded by the windblown sand. Therefore, the purposes of this work are to study the erosion wear and damage behaviors of different rail steels through the erosion testing, to explore the relationship between the mechanical properties of rail steels and their erosion behaviors, and to explain the erosion mode and the material removal mechanism of rail steels in the windblown sand environment. Method Based on the windblown sand environment in the Gobi areas, the natural aeolian sand in the Gobi area along the South Xinjiang Railway was selected as the erodent. The erosion specimens were taken from the rail heads. The erosion tests of hot-rolled U71Mn, hot-rolled U75V, heat-treated U75V, heat-treated U78CrV and an heat-treated hypereutectoid rail steel were conducted at the impact angles of 15°, 30°, 45°, 60°, 75°, and 90° using an air-sand jet erosion tester. The erosion rates of the rail steels were determined via the weightlessness measurement method. The surface and subsurface damage morphologies of the rail specimens after the tests were observed using a scanning electron microscope. Results With the increase in the cumulative mass of the sand particles, the erosion rates of rail steels fluctuated violently first, and then gradually became stable. The mass of the sand particles required for hot-rolled rail steel to reach the steady state was larger than that of heat-treated rail steel. With the increase in the impact angle, the steady state erosion rate was increased initially and then decreased. The maximum steady state erosion rate occurred between 30° and 45°. The windblown sand erosion wear resistance of the rail steels was ranked as: heat-treated hypereutectoid rail > heat-treated U78CrV > hot-rolled U71Mn > heat-treated U75V > hot-rolled U75V. The main erosion damage features at 45° impact angle were mainly platelet, shear crater, ploughing crater and plastic flow. The main erosion damage features at 90° impact angle were mainly platelet, indentation crater, plastic flow and crack. At the same impact angle, the erosion damage features in the steady state for different rail steels were relatively similar. The erosion wear resistance of hot-rolled rail steels was negatively correlated with their hardness and positively correlated with their ductility. The erosion wear resistance of heat-treated rail steels was positively correlated with their hardness, and there was no relatively uniform relationship with their ductility. Comparing to the influence of hardness, the ductility of hot-rolled rail steels had a greater influence on the erosion wear resistance. Comparing to the influence of ductility, the hardness of heat-treated rail steels had a greater effect on the erosion wear resistance. The erosion wear resistance of the U75V rail steel could be improved by online heat treatment. The erosion efficiency of all the rail steels was between 1.17% and 1.78%. The erosion mode of all the rail steels was ductile erosion, and the main erosion mechanism was the platelet mechanism. Conclusion The windblown sand erosion wear resistance of heat-treated rail steels was better than that of hot-rolled rail steels. The erosion wear resistance of different rail steels was ranked as: heat-treated hypereutectoid rail > heat-treated U78CrV > hot-rolled U71Mn > heat-treated U75V > hot-rolled U75V. Rail steels exhibited the ductile erosion mode when eroded by windblown sand, and the primary mechanism of material removal was platelet mechanism.