马氏体/贝氏体异种耐热钢焊接接头界面蠕变失效数值模拟

Numerical Simulation on Interfacial Creep Failure of Dissimilar Welded Joint between Martensitic and Bainitic Heat-resistant Steels

采用有限元法对高、中、低匹配马氏体T91与贝氏体G102异种耐热钢接头在560℃、不同外加轴向拉应力条件下的蠕变最大主应力、von Mises等效应力进行数值模拟,并通过加速试验对模拟结果进行验证。结果表明,低匹配接头焊缝/G102界面附近最大主应力数值很高,蠕变孔洞易于在焊缝/G102界面形成。高匹配接头焊缝/低强母材界面的最大应力和von Mises等效应力数值很高,孔洞易于形核、扩张。中匹配接头焊缝/G102界面附近最大主应力和von Mises等效应力最小。加速试验后低匹配接头焊缝/G102界面发生蠕变断裂,高匹配接头焊缝/G102界面处的蠕变孔洞几乎连成裂纹,中匹配接头焊缝/G102界面附近的晶界仅存在个别孤立蠕变孔洞,早期失效倾向最小。数值模拟结果与加速试验结果一致。

The maximum principal stresses,von Mises equivalent stresses in dissimilar welded joints between martensitic（T91） and bainitic heat-resistant steel（G102） with different welding creep strengths are simulated by using FEM under the conditions of 560 ℃ and applied stresses of 100 MPa,120 MPa and 140 MPa.Simulation results are validated with accelerating test.The results show that the maximum principal stress is quite high in the vicinity of weld/G102 interface for undermatching joint,and creep cavities are easy to form in the weld/G102 interface.The maximum principal stress and von Mises equivalent stress in the vicinity of weld/G102 interface for overmatching joint are high,and creep cavities are easy to form and expand.The maximum principal stress and von Mises equivalent stress of weld/G102 interface for medium-matching joint are the least among the three joints.The interfacial creep damage of undermatching welded joint is very serious,the creep cavities of weld/G102 interface nearly link to form creep cracks in overmatching joint.The creep damage and early failure tendency of medium-matching joint are the lowest among the three joints,and only isolated cavities are found in the test.And the results of numerical simulation are consistent with those of experiment.