12Cr/30Cr2Ni4MoV异质接头低周疲劳性能

文中研究了12Cr/30Cr2Ni4MoV异质焊接接头的显微组织、显微硬度和室温低周疲劳性能. 结果表明，母材12Cr的显微组织是板条状回火马氏体，母材30Cr2Ni4MoV是板条状回火马氏体和粒状回火贝氏体，过渡层和焊缝的显微组织为粒状回火贝氏体，且焊缝由柱状晶区与等轴晶区交替构成. 30Cr2Ni4MoV比12Cr有更高的显微硬度，过渡层的硬度最低，热影响区的显微硬度梯度变化. 12Cr，30Cr2Ni4MoV和过渡层的低周疲劳性能表现为循环软化特征，焊缝循环初期硬化随后软化；过渡层的疲劳过渡寿命最高；12Cr与过渡层之间的熔合界面是整个异质焊接接头低周疲劳最薄弱环节；焊缝柱状晶区的晶界或亚晶界分布的第二相粒子与基体的不协调变性，容易萌生疲劳裂纹.

Study on low-cycle fatigue property of 12Cr/30Cr2Ni4MoV heterogeneous joint

In this article, the microstructure, micro-hardness and low-cycle fatigue property of a 12Cr/30Cr2Ni4MoV welded joint have been studied. The results show that the microstructure of the 12Cr is lath tempered martensite, 30Cr2Ni4MoV is lath tempered martensite and granular tempered bainite. The microstructure of the buttering layer (BL) and weld metal (WM) is granular tempered bainite. WM is composed of columnar grain regions and equiaxed grain regions alternately. 30Cr2Ni4MoV has higher micro-hardness than 12Cr, and the BL is the lowest. Micro-hardness in the heat-affected zone (HAZ) is gradient change. 12Cr, 30Cr2Ni4MoV and BL show cyclic softening characteristics, while WM has initial cycle hardening and subsequent cyclic softening characteristics. BL has the highest fatigue transition life; the 12Cr/BL interface is the weakest link of the low-cycle fatigue of the entire heterogeneous welded joint. The second phase particles distributed in the grain boundary or sub-grain boundary of the columnar grains have uncoordinated deformation with the matrix of WM, which result in the initiation of fatigue cracks in second phase