异质梯度结构对高铁钢轨材料耐磨性的影响

Influence of heterogeneous gradient structure on wear resistance of high-speed rail materials

随着客运铁路运输朝着高速化的方向发展,轮轨之间剧烈的磨损会严重制约列车运行的安全性,因此需要提高钢轨材料的表面耐磨性能。基于此,采用表面机械研磨处理(Surface mechanical attrition treatment,SMAT)技术对U71Mn钢轨材料表面进行改性处理,利用扫描电镜、透射电镜、X射线衍射仪和微米划痕仪等表征了其表层异质梯度结构(HGS)的组织演变、力学性能和耐磨性。结果表明:经过表面改性处理后,U71Mn钢轨材料表层形成了约130μm厚的异质梯度结构;越靠近表层,材料的变形程度越大,珠光体内的片状渗碳体发生断裂和溶解,呈短条形或颗粒状,铁素体被挤压成细长的塑性流线,并出现亚晶粒。随着距离表面深度的增加,变形程度减弱,渗碳体片层不规则弯曲起皱,部分渗碳体碎裂。SMAT技术可以大幅提高U71Mn钢轨材料的耐磨性能,其磨损率较原始材料下降了89%。越靠近表面,U71Mn钢轨材料的硬度和断裂韧性越高,相较于基体分别提高了34.6%和30.5%。SMAT后钢轨材料的晶粒出现细化,位错大量增殖,因此具有异质梯度结构的U71Mn钢轨材料力学性能及耐磨性提高的主要原因是细晶强化和位错强化。

With the development of high-speed passenger railway transportation,severe wear between wheels and rails will seriously restrict the safety of train operation.Therefore,it is necessary to improve the surface wear resistance of rail materials.So,surface mechanical attrition treatment(SMAT)technology was used to modify the surface of U71Mn rail material,and microstructure evolution,mechanical properties and wear resistance of its surface heterogeneous gradient structure(HGS)were characterized using scanning electron microscopy,transmission electron microscopy,X-ray diffraction and micro scratch tester.The results show that after surface modification treatment,a heterogeneous gradient structure with a thickness of about 130μm is formed on the surface of the U71Mn rail material.The closer it is to the surface,the greater the degree of deformation of the material.The flake cementite inside the pearlite breaks and dissolves,forming short strips or granular shape.The ferrite is squeezed into slender plastic flow lines and sub-grains appear.As the depth from the surface increases,the degree of deformation weakens,the lamellar of cementite is irregularly bent and wrinkled,and some cementite is broken.SMAT technology can significantly improve the wear resistance of the U71Mn rail material,with a wear rate reduced by 89%compared to the original material.The closer to the surface,the higher the hardness and fracture toughness of the U71Mn rail material,which increase by 34.6%and 30.5%respectively compared to the matrix.After SMAT,the surface grains of the rail material is refined and the number of dislocation is greatly increased.Therefore,the main reason for the improved mechanical properties and wear resistance of the U71Mn rail material with heterogeneous gradient structure is the fine grain strengthening and dislocation strengthening.