铸钢表面镍基合金渗层的热疲劳行为

采用铸渗技术在铸钢ZGCr5Mo试样表面制备了镍基合金渗层,渗层的厚度为0.6—1.2 mm,考察了镍基合金渗层的热疲劳行为,用扫描电镜(SEM)、X射线衍射(XRD)对热疲劳循环后的渗层表面进行了形貌观察与成分分析。结果表明:在热循环次数低于20次时,表面仅发生了氧化现象,当热循环次数超过90次时,渗层表面出现微裂纹,随着循环次数的增加,在渗层与基体的侧表面上出现贯穿渗层与基体的微裂纹以及在渗层与基体的界面处的表面氧化膜层出现了平行于渗层表面以及发散的微裂纹;随着镍基合金渗层厚度的增加,出现微裂纹的热循环次数略有降低。表面的氧化膜层主要为镍、铬的氧化物以及镍铬的复杂氧化物。

The Thermal Fatigue Behavior of Ni-based Alloying Infiltrated Layer on Cast Steel Substrate

The Ni-based infiltrated layer was fabricated through vacuum infiltration casting technology on ZGCr5Mo substrate.The thickness of infiltrated layer was 0.6—1.2mm.The thermal cycling behavior was investigated.The surface appearance and composition of Ni-based infiltrated layer was studied by means of SEM and XRD.The results show that the oxidation happened only when the thermal cycling times was less than 20.The micro-crack appeared on the surface of infiltrated layer when thermal cycling times was more than 90.The micro-crack ran through the whole infiltrated layer to substrate.There were micro-cracks parallel to the surface of infiltrated layer and emanative micro-cracks at the interface between the infiltrated layer and substrate.The thermal cycling times was deceased with the increasing thickness of infiltrated layer.The main composition was oxides of Ni and Cr,complicated oxide of Ni/Cr.