Precipitation behavior and influence of Laves phase in martensitic heat resistant steel

The precipitation behavior and influence of Laves phase in martensitic heat resistant steel was studied by contrasting the whole martensitic microstructure and the martensitic microstructure which containing a small amount of delta ferrite. The Laves phase was observed by using a transmission electron microscope (TEM), and subsequent analysis is implemented in respect of the precipitation behavior of Laves phase in different microstructure and the influence of creep temperature and stress on the morphology and size of Laves phase. The results show that there are two mechanisms of the nucleation and growth for Laves phase in whole martensitic microstructure, one of which is that Laves phases occur alone on grain boundaries while the other one is that Laves phases are formed in the regions adjacent to M23C6particles. But in martensitic which contained a few delta ferrite, the Laves phase is nucleated preferentially inside the delta ferrite. The higher creep temperature and stress can promote the nucleation and growth of Laves phase. ©, 2015, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved.