DEVELOPMENT OF FERRITIC HEAT-RESISTANT STEELS BASED ON NEW MATERIALS DESIGN CONCEPT FOR ADVANCED HIGH EFFICIENCY POWER PLANTS

摘要

To save fossil fuel resources and to reduce CO_2 emission, considerable efforts have been directed toward the research and development of heat-resistant materials that can help in improving the energy efficiency of power plants by increasing their steam temperature and pressure. Instead of the conventional 9-12Cr ferritic heat-resistant steels with a tempered martensitic microstructure, the authors have proposed "Precipitation Strengthened 15Cr Ferritic Steel" based on the new material design concept that is a solid-solution treated ferrite matrix strengthened by intermetallic compounds. In this study, the creep strength of the developed 15Cr ferritic steels with various Ni contents was investigated. As a result of the creep tests for the 15Cr steels at 923, 973, 1023 K up to about 65 000 h, it was found that the creep strength of the 15Cr steels was two times higher than that of the conventional 9Cr ferric heat-resistant steels at every temperatures. The creep rupture lives of the steel were 10 to 100 times longer than that of the conventional versions. The creep rupture strength of the 15Cr steels after 100 000 h was estimated to be 100 to 130 MPa at 923 K and 45 to 70 MPa at 973 K from Larson-Miller parameter method. The authors believe the precipitation strengthened 15Cr ferritic steel is a candidate material of the high-temperature structural components in high-efficient thermal power plants.