分别采用钨极氩弧焊(TIG焊)和熔化极活性气体保护焊(MAG焊)方法制备了785 MPa级Fe-Cr-Ni-Mo系熔敷金属.利用扫描电子显微镜、透射电子显微镜和电子背散射衍射仪对熔敷金属的组织类型和晶体学特征进行了详细的表征分析，结果表明，采用不同焊接方法制备得到的熔敷金属组织均为贝氏体，但钨极氩弧焊熔敷金属(DM-TIG)中出现大量聚合贝氏体；由于焊接过程中使用的保护气体不同，熔化极活性气体保护焊熔敷金属(DM-MAG)中存在大量夹杂物. 经过电子背散射衍射分析结果表明，相比于DM-TIG，DM-MAG中由于存在大量自催化形核现象，晶体学取向非常复杂.力学性能测试结果表明，DM-MAG中大尺寸夹杂物在冲击过程中作为裂纹源，从而导致DM-MAG的韧性明显低于DM-TIG，实际工程应用中对于低温韧性要求较高的结构部件应合理选择焊接方法.
In this research, 785 MPa grade Fe-Cr-Ni-Mo deposited metals were prepared by tungsten inert gas (TIG) welding and metal active gas arc (MAG) welding processes, respectively. Scanning electron microscopy, transmission electron microscopy and electron backscatter diffraction were adopted to characterize the microstructure and crystallographic characteristics of the deposited metals. The results showed that the microstructure prepared by different welding processes composed of lath bainite. However, a large amount of coalesced bainite appeared in the microstructure of the TIG deposited metal (DM-TIG). In addition, there were a large number of inclusions in the MAG deposited metal (DM-MAG) due to the active shielding gas. After electron backscatter diffraction analysis, results indicated that the crystallographic orientation of DM-MAG was complex compared to DM-TIG due to the large number of autocatalytic nucleation. The results of the mechanical properties of different deposited metals indicted that the toughness of DM-TIG was significantly better than that of DM-MAG. This was due to the large-sized inclusions in DM-MAG, which became the source of cracks during the fracture process. In practical engineering application, welding method should be selected reasonably for components with high requirement of low temperature toughness.
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