Long-term creep-rupture strength prediction for modified 9Cr-1Mo ferritic steel and type 316L(N) austenitic stainless steel

The prediction of long-term creep-rupture strength values for mod. 9Cr-1Mo ferritic steel and 316L(N) austenitic stainless steel is made using several life prediction methodologies at 773, 823 and 873 K. Creep-rupture strength values have been predicted following the Larson-Miller parameter, the Orr-Sherby-Dorn parameter, artificial neural network, and Wilshire approaches for rupture lives up to 60 years (5.256 x 10(5)h) using creep-rupture data available in the literature. It has been demonstrated that the prediction of creep-rupture strength values using these approaches are comparable. Creep-rupture strength values have been also evaluated using linear extrapolation of average creep-rupture strength values given in French Nuclear Design Code RCC-MR for durations more than 3 x 10(5)h. Predicted creep-rupture strength values using the literature data are found to be higher than those obtained from RCC-MR for both 9Cr-1Mo steel and 316L(N) SS. This suggested that the RCC-MR data are conservative and can be safely used for a design life of 60 years.