Creep rupture behavior of welded Grade 91 steel

Creep rupture behavior of fusion welded Grade 91 steel was studied in the temperature range of 600 - 700 °C and at stresses of 50-200 MPa. The creep data were analyzed in terms of the Monkman-Grant relation and Larson-Miller parameter. The creep damage tolerance factor was used to identify the origin of creep damage. The creep damage was identified as the void growth in combination with microstructural degradation. The fracture surface morphology of the ruptured specimens was studied by scanning electron microscopy and deformed microstructure examined by transmission electron microscopy, to further elucidate the rupture mechanisms.