Microstructural evolution in high chromium steels

The 9 wt% Cr ferritic-martensitic steels with alloying additions of Mo, V and Nb have been widely used in the power generation industry for many years. The high temperature strength and creep resistance of the advanced high chromium steels come from the microstructure, which typically contains a tempered martensite matrix with a fine dispersion of secondary particles. However, the dislocation density and the type, size and distribution of second phase particles in the microstructure are functions of the applied heat treatments. The mechanical properties of these steels, in turn, can be very sensitive to the microstructure during high temperature service life and therefore it is important to understand both the microstructural evolution and mechanical properties of these steels as a function of service life. [Continues.]