Long Term Creep Behaviour and Microstructural Evolution of E911 Steel

摘要

The creep resistance of Grade E911 was demonstrated to be higher than that of Grade P91: 600℃/101MPa/10~5h for Grade E911 and 600℃/93MPa/10~5h for Grade P91. However, the differences are strongly reduced at 650℃. The higher creep resistance of E911 steel was related to the addition of W, which promotes the precipitation of Laves phase during creep service. No coarsening of MX carbides was observed, while the mean diameter of M_(23)C_6 remains below 200 nm and 400 nm, respectively, at 600℃ and 650℃, even after a very long exposure. An excessive coarsening of Laves phase, which grows up to micrometric dimensions, was measured at 650℃, with the result of a loss in creep resistance and ductility after 10,000 hours. Below 610℃ the microstructural stability of this steel during service is guaranteed for very long time.