Creep crack propagation in austenitic stainless steel at elevated temperatures

Creep crack propagation behavior at high temperature was investigated for type 304 stainless steel. The present experiment reveals that creep crack propagation is explained better in terms of the stress intensity factor K than in terms of the net section stress sigmasub(net). The rate of the creep crack propagation is represented by the Arrhenius equation and the activation energy is found to be higher in comparison with the case of fatigue. Main cracks extend by means of joining micro-cracks initiated at the vicinity of the main crack tip. Creep rupture occurs when the value of the stress intensity factor reaches its critical value which increases with decreasing temperature but is independent of stress level. It is found that the creep rupture time is expressed as a function of initial stress and initial crack size, and good agreement is obtained between observed and calculated time to rupture. (author)