Effects of cyclic deformation on subgrain evolution and creep in 9-12% Cr-steels

Power plant components from modern 9-12% CrMoV-steels having fine precipitate stabilized subgrain structure undergo cyclic deformation as well as creep during service. The present work studies changes in subgrain structure due to cyclic straining and their effects on the creep behaviour in 12CrMoWVNbN10-1-1 steel. It was found that the cyclic plastic straining causes significant coarsening of the subgrain structure. Presence of hold periods during deformation significantly increases the extent of coarsening. Evolution of subgrain structure during cyclic deformation has been treated by extending the phenomenological law known from creep. Subgrain coarsening induced by cyclic deformation leads to significant increase in the resistance against creep.