针对ERNiCrFe-13焊丝熔敷金属拉伸过程中的微观组织演变规律和微裂纹的萌生扩展机制，采用SEM原位拉伸结合扫描电子显微镜(scanning electron microscope，SEM)观察和能谱(energy dispersive spectrometer，EDS)分析对熔敷金属组织及断裂行为等进行分析.结果表明，ERNiCrFe-13焊丝熔敷金属组织主要由柱状晶γ相(NiCrFe固溶体)、枝晶间富Nb和Mo元素的Laves相(Cr,Fe,Ni)2(Nb,Mo)、MC碳化物与共晶组织组成，Laves相的形成主要与凝固过程中Nb和Mo元素的偏析有关，且具有尺寸效应，水平方向Laves相尺寸大于4 μm易发生开裂，断裂机制为枝晶间析出相在切应力作用下本体断裂萌生微裂纹，在轴向拉应力的作用下进一步沿晶界扩展连通至断裂失效，断口呈韧性断裂，碳化物偏析(NbC、TiC)和大尺寸Laves相是晶界裂纹产生的主要原因.
The evolution of microstructure and the initiation and propagation mechanism of microcracks during the tensile process of ERNiCrFe-13 welding wire deposited metal. The microstructure and fracture behavior of deposited metal were studied by in-situ tensile scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the microstructure of ERNiCrFe-13 welding wire deposited metal is mainly composed of columnar dendrite γ phase (NiCrFe solid solution), Nb and Mo rich in Laves phase (Cr,Fe,Ni)2(Ti,Mo), MC carbides and eutectic structure in the interdendritic. The formation of Laves phase is mainly related to the segregation of Nb and Mo elements during solidification and has a size effect. Horizontal Laves phase size larger than 4 μm is prone to cracking. The fracture mechanism is the initiation of microcracks in the interdendrite precipitated phase under shear stress. Under the action of axial tensile stress, the connection is further extended along grain boundaries to fracture failure. The fracture is ductile and carbide segregation (NbC, TiC) and large Laves phase are the main causes of grain boundary cracks.
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