Abstract
Specimens of a Cr-M-V rotor steel with creep rupture periods up to 100000 h have been examined metallographically in order to clarify their creep fracture mechanisms and to construct creep fracture mechanism maps for the steel which show the dominant regions of each mechanism. The creep fracture mechanism maps have been drawn taking stress as y-axis and time to rupture as x-axis, and also stress as y-axis and testing temperature as x-axis. The constructed maps include three different creep fracture mechanism fields: transgranular creep fracture, intergranular creep fracture with cavitation and rupture with dynamic recrystallization. The maps indicate that the steel in power plants is being used under the conditions within the field of intergranular creep fracture with cavitation. This means that long time use of the steel under the conditions could cause extensive cavitation and ductility minimum.
