“…To provide pertinent combined properties under supercritical steam up to 650 o C, the microstructure of the materials should be composed of a ferritic matrix in martensite morphology with a large amount of phase boundaries, i.e., prior grain boundary (PAGB), lath boundary, subgrain boundary and second phase boundary (Panait et al, 2010;Rojas et al, 2011). In addition, the composition should contain high Cr to ensure high corrosion resistance and the precipitation of carbides (Chen et al, 2006;Shen et al, 2009;Zhong et al, 2012). Since the beginning of the twentieth century, researchers have conducted microstructural analyses pertaining to strengthening and degradation mechanisms using optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM).…”