Abstract
The creep strength enhanced martensitic steels are key material for the main power generating units in ultra-supercritical plants. Studies on the evaluation of their creep rupture life show there is an overestimation of rupture life after long-term creep, which is known as premature failure. However, the microstructural origin of the premature failure remains unclear. Here in this study, we have carefully investigated the microstructural transformations and their influences on creep rupture behavior, showing that the evolution of martensite and M23C6 carbides as well as Laves phase are responsible for the premature failure. By using multi-step TTP-LMP method, we confirmed a three-stage creep rupture behavior under different stress regions. Further quantitative analysis showed that the coarsening of M23C6 carbides and recovery of martensite exert equal and dominant effects on the premature failure in the medium stress region, while precipitation and coarsening of Laves phase are responsible for the premature failure in the low stress region.
Published Version
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