Ferritic steels are widely used in steam turbine components such as boilers, pressure vessels, heat exchangers, and other high-temperature components. One of the critical properties of such materials in the application is their long-term creep rupture strength. 9Cr-1Mo-V-Nb is considered as the benchmark in the 9Cr steel class. Although the 9Cr-1Mo-V-Nb steel is designed to have a tempered martensitic structure with precipitation of M23C6 and MX to increase its creep-resistance, its microstructure will change due to the evolution of precipitates at high-temperature under stress. Notably, intermetallic particles, i.e., Laves phase [(FeCr)2Mo], which are not present in the original state of the material, will form during long-term creep, which can shorten the creep life. In this study, the creep behavior of 9Cr-1Mo-V-Nb steel aged for 5,000 hours at 600 o C is evaluated. Microstructure examination is also conducted with regards to the Laves phase formation and its microstructural locations. The creep behavior is analyzed using a mechanism-based true-stress creep model with the consideration of dislocation climb, dislocation glide, and grain boundary sliding.

14th International Conference on Fracture, ICF 2017
Department of Mechanical and Aerospace Engineering

Zhang, X.Z. (X. Z.), Wu, X.J. (X. J.), Liu, R, Liu, J. (J.), & Yao, M.X. (Matthew X.). (2017). Microstructure and modeling of creep resistance of modified 9Cr-1Mo steel. In ICF 2017 - 14th International Conference on Fracture (pp. 712–713).