目的 研究12Cr1MoV焊接接头在NaOH溶液中的应力腐蚀裂纹扩展行为及机理。方法 采用三点弯加载的方法，对不同初始应力强度因子(40、50、60 MPa.mm^1/2)条件下的12Cr1MoV焊接接头在NaOH溶液(80 ℃、质量分数为20%)中的应力腐蚀裂纹扩展行为进行研究，使用SEM和电子背散射衍射(EBSD)等方法，分析应力腐蚀裂纹扩展路径和断口形貌。结果 接头应力腐蚀裂纹扩展速率随着初始应力强度因子的增大而增大，最高达到11.189′10^–7 mm/s，但增大的趋势逐渐减缓。应力腐蚀裂纹呈树枝状扩展，且应力强度因子越大，主裂纹出现分支越早，裂纹扩展越宽。主裂纹在扩展过程中也产生了部分不连续的裂纹和与其在局部扩展方向一致的“跳跃”微裂纹。应力强度因子较高时，裂纹的断口呈冰糖状形貌，为沿晶裂纹，在较低应力强度因子(KI = 40 MPa.mm^1/2)条件下，裂纹断口表现出以沿晶为主、穿晶为辅的混合断裂模式。结论 随着初始应力强度因子的增大，应力腐蚀裂纹扩展速率提高，主裂纹出现分支越早，裂纹扩展越宽。焊缝应力腐蚀裂纹沿着原始奥氏体晶界，在阳极溶解和氢致裂纹的共同作用下进行扩展，其中以阳极溶解为主。

This paper is to study the stress corrosion crack propagation behavior and mechanism of 12Cr1MoV welded joints in NaOH solution. The stress corrosion crack propagation behavior of 12Cr1MoV welded joints under different initial stress intensity factors (40, 50 and 60 MPa.mm1/2) in NaOH solution (80 ℃, 20wt.%) was carried out by three-point bending loading method. The crack propagation path and fracture morphology were analyzed by SEM and electron back-scatter diffraction (EBSD). The growth rate of stress corrosion crack increased with the increase of the initial stress intensity factor, and the maximum reaches 11.189′10–7 mm/s, but the growth trend slowed down gradually. The stress corrosion crack propagated in a dendritic manner, and the larger the stress intensity factor was, the earlier the main crack branched and the wider the crack expanded. Partial discontinuous cracks and “jumping” micro-cracks also generated during the propagation of the main crack. At high stress intensity factor condition, the fracture surface of the crack presented ice-sugar morphology, which belonged to the intergranular fracture. Under the condition of lower stress intensity factor (KI = 40 MPa.mm1/2), the fracture presented most intercrystalline assistant with some transgranular. With the increase of initial stress intensity factor is, the growth rate of stress corrosion crack increases, and the earlier the main crack branches, the wider the crack grows. Under the joint action of anodic dissolution and hydrogen-induced cracking, the stress corrosion crack of the weld propagates along the original austenite grain boundary, of which the anodic dissolution is the main one.