h Research and Development of Heat-Resistant Materials for Advanced USC Power Plants with Steam Temperatures of 700 °C and Above

Materials-development projects for advanced ultra-supercritical (A-USC) power plants with steam temperatures of 700 degrees C and above have been performed in order to achieve high efficiency and low CO2 emissions in Europe, the US, Japan, and recently in China and India as well. These projects involve the replacement of martensitic 9%-12% Cr steels with nickel (Ni)-base alloys for the highest temperature boiler and turbine components in order to provide sufficient creep strength at 700 degrees C and above. To minimize the requirement for expensive Ni-base alloys, martensitic 9%-12% Cr steels can be applied to the next highest temperature components of an A-USC power plant, up to a maximum of 650 degrees C. This paper comprehensively describes the research and development of Ni-base alloys and martensitic 9%-12% Cr steels for thick section boiler and turbine components of A-USC power plants, mainly focusing on the long-term creep-rupture strength of base metal and welded joints, strength loss in welded joints, creep-fatigue properties, and microstructure evolution during exposure at elevated temperatures.