Microstructural evolution by heavy damage accumulation on high chromium oxide dispersion strengthening (ODS) ferritic steels

As a next generation energy system, nuclear power still has enough attraction and advantages from the view of energy source availability, climate change, air quality and energy security. In the international nuclear energy system research and development named Generation IV, super-critical pressurized water reactor (SCPWR) has been one of powerful candidates for the future energy system. Recently, oxide-dispersion strengthening (ODS) ferritic steels with high corrosion resistance have been developed for the core material in SCPWR. The reactor core materials in the SCPWR are required to have excellent resistance against corrosion in coolant and irradiation damage accumulation. In this work, a high corrosion resistant ODS steel, 19Cr-2W-4Al ODS steel was selected to study the irradiation effect on ODS steels. The ODS steels were consolidated by the hot extrusion method. The analysis equipments as FE-TEM with EDX, FE-SEM and nano-indentation were used for the investigation of microstructure and mechanical property changes after ion irradiations. The TEM investigation revealed the three kinds of dispersed particles existed in 19Cr-2W-4Al ODS steel. The finest yttrium-aluminum complex oxides were supposed to contribute to keep mechanical properties. The irradiation experiment at 500°C, 20 dpa did not affect microstructure significantly. At 700°C, 20 dpa, the secondary phase of chromium-rich precipitated on the grain boundaries and in grains, the yttrium-aluminum complex oxides still kept fine.