Microstructure evolution and life assessment of T92 steel during long-term creep

Standard tests for creep and rupture strength were carried out on T92 martensitic heat-resistant steel at the temperatures of 600, 650, and 700 °C and stress levels of 46-200 MPa. The creep life of T92 steel was estimated through the Larson-Miller parameter, which was calculated from the aging temperature and aging time. Crystal structures and morphologies of precipitate phases after creep were investigated by scanning electron microscopy and transmission electron microscopy, and the composition was analyzed by energy dispersive X-ray spectrometry. Degeneration processes after creep exposure of the martensitic microstructure, namely, martensitic substructure recovery, as well as coarsening and precipitation of second phases, were also observed.