Cyclic softening as a parameter for prediction of remnant creep rupture life of a Indian reduced activation ferritic–martensitic (IN-RAFM) steel subjected to fatigue exposures

Sequential fatigue-creep tests were conducted on Indian reduced activation ferritic–martensitic steel at 823K leading to sharp decrease in residual creep life with increase in prior fatigue exposures. Extensive recovery of martensitic-lath structure taking place during fatigue deformation, manifested as cyclic softening in the cyclic stress response, shortens the residual creep life. Based on the experimental results, cyclic softening occurring during fatigue stage can be correlated with residual creep life, evolving in an empirical model which predicts residual creep life as a function of cyclic softening. Predicted creep lives for specimens pre-cycled at various strain amplitudes are explained on the basis of mechanism of cyclic softening.