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 a
nd lower rupture life and ductility than the base metal and weld metal. Cre
ep tests were performed on the simulated heat affected zone (HAZ) structure
s of the weld joint (viz. coarse-grain bainite, fine-grain bainite and inte
rcritical structure) at 823 K. The coarse-grain bainitic HAZ possessed high
er creep strength and the intercritical HAZ possessed lower creep strength
than the base metal and weld metal, whereas the fine-grain bainitic HAZ exh
ibited creep strength comparable to that of the base and weld metals. A mod
ified composite model with an interaction parameter was used successfully f
or estimating the weld joint properties from the properties of the constitu
ents of the joint. Properties estimated were steady state creep rate, ruptu
re life and rupture ductility. (C) 2001 Elsevier Science Ltd. All rights re
served.