High chromium ferritic martensitic (F/M) alloys are widely used in high temperature components of the power plants due their exhibit high temperature properties. Long creep time and the elevate temperatures involve that the F/M steels can present a loss of creep strength as the consequence of the precipitation of new phases, the coarsening of M23C6 carbides and the dissolution of the fine dispersed MX carbonitrides. To obtain a more stable microstructure exist different methods such the use of thermo-mechanical treatments (TMT) which can improve the mechanical properties due to can be produce a dense dispersion of nano-sized precipitates in the steels during the TMT.

This work is focused on the study of the effect of a thermomechanical treatment optimization in the enhanced the creep strength of a conventional F/M grade 91 steel via small punch creep. Conventional creep results were also included. Small punch creep results show a great improvement of creep strength with elevated values of the time of rupture in comparison with the conventional grade 91 steels, according with the conventional creep tests results.