Microstructural analysis on creep properties of dissimilar materials joints between T92 martensitic and HR3C austenitic steels

This paper reports the creep rupture behaviors of T92/HR3C dissimilar materials joints. HR3C austenitic steel is welded with T92 martensitic steel to obtain T92/HR3C dissimilar materials joints. After welding, creep test is carried out at 625 °C in the stress range 110–180 MPa. The rupture locations of creep specimens are examined by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the creep rupture mechanism of the joint is dependent on stress. When stresses ≥140 MPa, rupture location is at the T92 base material part and the connection of adjacent dimples results in transcrystalline fracture. For stresses <140 MPa, rupture location is at the T92 coarse-grained HAZ (CGHAZ) and M23C6 particles grown up as well as Laves phase ((Fe, Cr)2 (W, Mo)) precipitation on grain boundaries leads to the creep cavities and intergranular fracture.