辙叉用高锰钢滚动接触疲劳表层硬化特征及组织分析

采用光学显微镜(OM)、透射电镜(TEM)以及X射线衍射仪(XRD)等对辙叉用高锰钢试样的滚动接触疲劳特性进行了分析。研究表明,高锰钢疲劳表层硬度最大值为580～690 HV0.3,硬化层深度为1～2 mm,硬化机制以孪晶、位错和层错为主,缺少冲击载荷是硬化规律异于高锰钢辙叉实际服役条件下硬化规律的主要原因。在100 ℃及1800 MPa的接触应力下循环3.5×10⁶周次,高锰钢发生了时效,析出的碳化物为体心结构的Fe_0.6Mn_5.4C₂。接触应力的存在降低了高锰钢析出碳化物的温度,即在高锰钢时效所需的能量中,额外机械能的增加可以使所需的热能相对地减少。

Microstructure analysis and rolling contact fatigue surface hardening characteristics of high manganese steel used for railway crossing

Rolling contact fatigue characteristics of high manganese steel specimen for railway crossing were analyzed by means of metallographic microscope (OM), transmission electron microscope (TEM) and X-ray diffractometer (XRD). The results show that the maximum hardness of fatigue surface of the high manganese steel is 580-690 HV0.3, and the depth of hardening layer is 1-2 mm. The hardening mechanism is mainly twins, dislocation and stacking fault. Lacking of impact load is the major reason that why the hardening law is different from that under the actual service condition of high manganese steel railway crossing. At 100 ℃ and under the contact stress of 1800 MPa for 3.5×10⁶ cycles, aging of high manganese steel occurs and the precipitated carbide is Fe_0.6Mn_5.4C₂ with body center structure. The existence of contact stress reduces the temperature of carbide precipitation needed in high manganese steel, which indicates that the increase of additional mechanical energy can reduce the required thermal energy relatively.