Microstructural evolution and oxidation behavior of 13Cr-ODS steel tube after exposure at 1200 °C

• Thermal exposure at 1200 °C triggers a transition from deformed lamellar grains to multimodal equiaxed grains. • Nanoparticles pin boundaries to delay recrystallization, localized nanoparticle coarsening eventually allows grain growth. • Present 13Cr-ODS steel follows parabolic oxidation kinetics at 1200 °C with a high rate constant of K p = 54.32 mg 2 cm −4 min −1 , • A complex bilayer oxide scale consisting of an outer iron oxide layer and a chromium-rich inner spinel layer. Oxide dispersion-strengthened (ODS) steels are attractive candidates for fuel cladding in Generation IV reactors, due to their exceptional radiation resistance and high-temperature stability. This study investigates the microstructural evolution and oxidation kinetics of industrial pilgered 13Cr-ODS steel tubes during isothermal exposure at 1200 °C. Results indicate that the initially deformed, fibrous grains undergo partial recrystallization and significant grain coarsening after 20 h of exposure. This structural degradation is driven by a compromise between high stored deformation energy and Zener pinning from nano-oxides. High-temperature oxidation follows a transition from linear to parabolic growth kinetics, with a rate constant of approximately K p = 54.32 mg 2 cm −4 min −1 . Characterization reveals a non-protective bilayer oxide scale consisting of an outer Fe 3 O 4 layer and a porous inner FeCr 2 O 4 spinel layer.