Creep fatigue crack growth in 0·5Cr–Mo–V steel

Abstract

An investigation is presented of crack growth in a normalised and tempered 0·5Cr–Mo–V steel under cyclic displacement controlled loading conditions at 565–600°C. A transition from fatigue to creep dominated behaviour was observed as the duration of the tensile dwell period in the cycle was increased. This change was a result of a progressive increase in the extent of crack tip grain boundary damage accumulation which, in the long dwell tests, was sufficient to give rise to crack extension directly. Time dependent crack propagation rates during the dwells of the long dwell tests were found to approach those determined for static load conditions. No evidence was found for a significant creep-fatigue interaction and it appears that overall crack growth rates are determined by crack tip oxidation and damage accumulation processes.

MST/756