Porosity prediction in supercritical water exposed ferritic/martensitic steel HCM12A

Pores are often observed in magnetite, a major oxidation product of ferritic/martensitic steels. Due to the detrimental effects of pores on the stability of the oxide and the detrimental effect of an unstable oxide on an engineering structural material’s performance, understanding the mechanism and location of the formation of porosity is critical. A methodology is developed in the present study to predict the pore location based on the diffusion mechanism of Fe in magnetite. This methodology is illustrated with an important engineering ferritic/martensitic steel HCM12A which is exposed to supercritical water. The predicted results are in good agreement with the experimental results. The location of pores is found to be roughly dependent upon oxygen partial pressure but not upon exposure time. This methodology can be used as an intelligent guide to control environment parameters such as oxygen partial pressure, and thus control the occurrence and location of pores.