Microstructural evolution related to the mechanical response from isothermal dwell-fatigue testing at 700 °C of two austenitic steels, Esshete 1250 and Sanicro 25, is reported. Coherent Cu-precipitates incoherent Nb-carbides were found impede dislocation motion, increase hardening improving high temperature properties 25. Sparsely placed intergranular Cr- made susceptible creep damage crack pro...