Abstract
Advanced high Cr ferritic steel have a complex lath martensitic structure consisting of several microstructural units, i,e., in the order of their size, fine lath, block and/or packet including several laths, and prior austenite grain which is the largest unit. In addition, precipitation, solid-solution and dispersion strengthening contribute to their strength. However, it is by no means easy to separate the contributions of such strengthening factors and quantitatively understand them because of extremely fine and complicated microstructure. In this study, the instrumented indentation test was carried out under a wide variety of maximum indentation loads using the interrupted creep specimens to clarify the contributions of block to their strength and/or material degradation.
