Study on the nucleation and growth of Laves phase in a 10% Cr martensite ferritic steel after long-term aging

The nucleation and growth of Laves phase in a 10% Cr martensite ferritic steel after long-term aging have been investigated in this paper. Laves phase, (Fe, Cr)(2) (Mo, W), was observed after long-term (>750 h) aging at 650 degrees C. It is found that Laves phases prefer to locate at prior austenite grain boundaries and martensite lath boundaries, especially, most of them precipitate at grain boundaries with a misorientation angle of 40-60 degrees and only a small amount of them at 3-10 degrees. Moreover, the size of Laves phase at 40-60 degrees grain boundaries is larger than that at 3-10 degrees grain boundaries. In addition, some Laves phases are formed in the regions adjacent to M23C6 particles, with increasing aging time they will gradually swallow the Cr-rich M23C6 carbides in close vicinity, resulting in carbon atoms segregation on the vicinity of phase interfaces between Laves phase and alpha-Fe. (C) 2014 Elsevier B.V. All rights reserved.