A comparison of microstructure evolution due to fatigue loading in Eurofer 97 and ODS Eurofer steels

摘要

The Eurofer 97 steel and its variant strengthened by fine oxide dispersion (ODS Eurofer) were investigated. Both variants were subjected to the cyclic loading at room temperature. Moreover, the Eurofer 97 steel was exposed to the cyclic loading at 550°C and the ODS Eurofer steel at 650 and 750 °C. Continuous cyclic softening was found in both variants. Nevertheless, addition of 0.3 wt% of Y2O3 significantly reduces softening rate in the ODS Eurofer compared with the Eurofer 97 steel. Microstructure evolution and the role of oxide dispersion were investigated by means of transmission electron microscopy. It was observed the oxide dispersion suppresses grain growth in the ODS Eurofer steel and thus possible operating temperature is higher. The oxide particles remain stable up to highest temperature studied. The microstructural aspects are discussed in relation to the cyclic behavior of both steels.