Comparison of various 9-12%Cr steels under fatigue and creep-fatigue loadings at high temperature

► The cyclic softening is intrinsic to tempered martensitic lath/subgrain structure. ► It is due to the decrease of dislocation density and to the subgrain coarsening. ► Optimizing the creep resistance do not limit the cyclic softening effect. ► Better initial creep properties lead to correct remaining creep strength after cycling.