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 °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° and only a small amount of them at 3-10°. Moreover, the size of Laves phase at 40-60° grain boundaries is larger than that at 3-10° 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 α-Fe.