Si-containing 9Cr ODS steel designed for high temperature application in lead-cooled fast reactor

The oxide-dispersion strengthened (ODS) ferritic steels have been considered as promising candidate structural materials for liquid lead-bismuth eutectic (LBE) cooled reactors, and the corrosion of the ODS steel in liquid LBE presents a critical challenge. In order to improve the corrosion resistance of the ODS steel, a type of Y-Si-O strengthened ODS steel was designed and fabricated. The grain structure and dispersed nanoparticles were carefully characterized by the scanning electron microscope (SEM), the transmission electron microscope (TEM), the high-resolution transmission electron microscope (HRTEM) and the atomic probe tomography (APT) methods. Y2Si2O7 and Y2SiO5 nanoparticles both with monoclinic cubic crystal structure were found to be dominated in the matrix. And the number density and average diameter of the distributed nanoparticles were counted to be 1.8 × 1024 m−3 and ∼6 nm, respectively. The three dimensions APT reconstruction revealed that the as-received ODS alloy contained a high number density of nanometer scale yttrium-, silicon-, vanadium-, and oxygen-enriched nano-particles Furthermore, the high temperature property and corrosion resistance of the ODS steel were evaluated preliminarily. The miniature specimen tensile tests performed at 550 °C showed satisfactory high tensile strength of the ODS steel. The corrosion resistance was significantly improved by the addition of silicon according to the test of 1000 h exposure to liquid LBE.