A fracture mechanics characterization of creep crack growth in incoloy 800 H

Creep crack growth under constant and variable loading conditions is investigated at 800 degress C for an Alloy 800 H. The crack growth rates for steady state creep conditions determined with specimens of different sizes cover a range of 10 over the minus 4 power mm/s. They are correlated with the loading parameter C-integral by a power law independent of specimen size and loading conditions. The correlation with the stress intensity factor K is worse. The results are in agreement with theoretical models and they show the capability of the C-integral concept to describe creep crack growth under steady state creep conditions and large creep deformations. Consequently it should be possible to assess defects and to predict (residual) life times for flawed structures under such conditions.