|About this Abstract
|MS&T22: Materials Science & Technology
|Resisting Degradation from the Environment: A Symposium Honoring Carolyn M. Hansson’s Research and Pioneering Experiences as a Woman in STEM
|Characterization of Internal Oxidation in Alloy 690 and Model Ni Alloys
|Masoud Zakeri, Ibrahim Ogunsanya, Ali Ashrafriahi, Roger Newman
|On-Site Speaker (Planned)
Oxidation behavior of Alloy 690 and model Ni alloys (Ni-30Cr-10Fe and Ni-35Cr-10Fe) was investigated after exposure to hydrogenated steam at 480 °C and 1 atm, considered to simulate primary water in pressurized water reactor. The alloys underwent internal oxidation intragranularly, resulting in the expulsion of Ni to the surface. In Alloy 690, protective external Cr-rich oxides formed around grain boundaries and hindered oxygen penetration and intergranular oxidation. Over time, a compact Cr-rich healing layer developed at internal oxidation front initiating at the grain boundary surface oxide, effectively stopping further internal oxidation penetration into the bulk alloy. In Ni-30Cr-10Fe and Ni-35Cr-10Fe, their increased Cr concentration resulted in increased intergranular carbides. These carbides served as Cr-reservoir and caused higher outward Cr flux and significant reduction of internal oxidation depth. Short circuit diffusion along grain boundaries and diffusion-induced grain boundary migration dramatically increased diffusion of reactive components and promoted protective oxide layer formation.