Stress Dependence of Microstructural Evolution in Heat Resistant Steels
The state of the microstructure of ferritic heat resistant steels during creep was evaluate by the system free energy, which composes mainly chemical free energy, surface energy and elastic strain energy, and its stress dependence was expressed quantitatively by using a relaxation time. The steels used in this study were P91 (9Cr-1Mo-C-N-V-Nb) steel and P92 (9Cr-Mo-W-C-N-V-Nb-B) steel. The obtained results are as follows: (1) the relaxation time of elastic strain energy was expressed as a function of stress and temperature, (2) surface energy of P92 scarcely decreased during creep due to the formation of the Laves phase, and (3) the relaxation time of the chemical free energy in P92 was larger than that in P91.
Jian-Feng Nie and Allan Morton
Y. Murata et al., "Stress Dependence of Microstructural Evolution in Heat Resistant Steels ", Materials Science Forum, Vols. 654-656, pp. 190-193, 2010