Prediction of creep deformation and rupture behaviour of 2.25Cr–1Mo weld joint

Abstract

The evaluation of the creep properties of 2.25Cr–1Mo steel base metal, weld metal and weld joint at 773, 823 and 873 K over a stress range 80–300 MPa was carried out. The weld joint exhibited significantly higher creep rate and lower rupture life and ductility than the base metal and weld metal. Creep tests were performed on the simulated heat affected zone (HAZ) structures of the weld joint (viz. coarse-grain bainite, fine-grain bainite and intercritical structure) at 823 K. The coarse-grain bainitic HAZ possessed higher creep strength and the intercritical HAZ possessed lower creep strength than the base metal and weld metal, whereas the fine-grain bainitic HAZ exhibited creep strength comparable to that of the base and weld metals. A modified composite model with an interaction parameter was used successfully for estimating the weld joint properties from the properties of the constituents of the joint. Properties estimated were steady state creep rate, rupture life and rupture ductility.