The evaluation of material degradation in modified 9Cr-1Mo steel by the electrochemical technique

Evolution of microstructure due to service exposure to high temperature has a strong effect performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of Fe2Mo-type laves phases and coarsening of M23C6-type carbides is the primary cause of degradation of mechanical properties such as creep resistance, tensile strength and toughness. Creep tests have been carried out on pre-aging modified 9Cr-1Mo steels to examine the effect of pre-aging and stress on the creep strength. Based on the results, a nondestructive procedure, where electrochemical technique that quantitatively detect laves phases and M23C6-type carbides in a material is used, has been proposed to evaluate a residual creep life of modified 9Cr-1Mo steels.