Abstract: Creep finite element method(FEM) model of dissimilar welded joint between martensitic heat-resistant steel (T91) and austenitic(HR3C) is established. The maximum principal stress, von Mises equivalent stress and stress triaxiality is simulated at 600 ℃ and in the inner pressure of 42.26 MPa. The results show that the peaks of the maximum principal stresses are in the interface of weld/T91 and HR3C/weld in inner surface, and in the vicinity of weld/T91 interface in the distance of 2.96 mm away from outer surface. The creep cavities are ease to form in the weld/T91 interface in inner surface and in the place of 2.96 mm away from outer surface. In turn, in the weld/T91 interface of 1.29 mm away from inner surface, outer surface and 2.96 mm away from outer surface. The higher von Mises equivalent stress is in the weld/T91 interface of inner surface, and cavities are ease to expand. In turn, in the weld/T91 interface of 1.29 mm away from inner surface, outer surface and 2.96 mm away from outer surface. The stress triaxiality in the weld/T91 interface of inner surface is quit high, creep cavities are ease to link into interfacial creep cracks. And that, the stress triaxiality in the fine grain heat affected zone(HAZ) of 1.29 mm away from inner surface and 2.96 mm way from outer surface are also quit high, accordingly, creep cavities are ease to take the form of type IV creep crack. Therefore, using stress triaxiality to describing creep cavity expansion and crack development of the weld/T91 interface and fine grain HAZ is more reasonable for dissimilar welded joint between T91 and HR3C, and the numerical simulating results are good in agreement with those of experiment.

Key words: Austenitic heat-resistant steel, Martensitic heat-resistant steel, Maximum principal stress, Stress triaxiality, von Mises equivalent stress