Creep and Fatigue Properties of Newly Developed Ferritic Heat-Resisting Steels for Ultra Super Critical (USC) Power Plants

Abstract

This paper studies creep, fatigue and creep-fatigue interaction properties of several ferritic steels such as conventional Mod. 9Cr-1Mo, 9-12Cr-2W steels, newly produced boron- or palladium-added 9Cr-3W steels, high strength oxide dispersion strengthened (ODS) ferritic steels, and a precipitation hardening carbon-free martensitic steel. From the tests, two conclusions were derived to improve the creep-fatigue interaction strength. One is to have high creep ductility, and second is to decrease plastic strain of cyclic deformation by ultra high strengthening. From a viewpoint of evaluation of the creep-fatigue life, the analysis by ductility normalized strainrange partitioning method explained well the effects of creep ductility and strength of the materials on the creep-fatigue interaction.