Materials-development projects for advanced ultra-supercritical(A-USC) power plants with steam temperatures of 700℃ and above have been performed in order to achieve high efficiency and low CO_2 emissions in Europe, ...Materials-development projects for advanced ultra-supercritical(A-USC) power plants with steam temperatures of 700℃ and above have been performed in order to achieve high efficiency and low CO_2 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℃ 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℃. 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.展开更多
The X80 pipeline steel was welded with the way of submerged arc welding. The SST （slow strain test） of the welded joint samples in the air, NACE （National Association of Corrosion Engineers） solution （no H2S）, N...The X80 pipeline steel was welded with the way of submerged arc welding. The SST （slow strain test） of the welded joint samples in the air, NACE （National Association of Corrosion Engineers） solution （no H2S）, NACE solution （saturated H2S） was performed to research the sensibility index of SCC （stress corrosion cracking） Iscc. The morphologies of the welded joint fractures and the fracture modes were observed with SEM （scanning electron microscope）, and the fracture chemical compositions were analyzed with EDS （energy dispersive spectrometer）, respectively. The fracture mechanisms of the welded joints were discussed. The results show that sensibility index of SCC in the air is not obvious, the fracture is dimple, and the mode of fracture is ductile fracture. The sensibility index of SCC in NACE solution （no H2S） is 13.21%, the stress corrosion is not obvious. The sample fracture shows quasi cleavage＋dimple, and the fracture mode is toughness＋brittle rupture. The sensibility index of SCC in NACE solution （saturated H2S） is 56.94%, the plastic loss is the most serious, appearing an obvious stress corrosion tendency, and there is no obvious necking phenomenon. The fracture mode is brittle fracture, and the sample fracture has a high sulfur concentration, prompting S to a aliquation of crisp crystal in the welded zone, and making its mechanical properties worsen.展开更多
文摘Materials-development projects for advanced ultra-supercritical(A-USC) power plants with steam temperatures of 700℃ and above have been performed in order to achieve high efficiency and low CO_2 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℃ 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℃. 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.
基金Item Sponsored by Natural Science Foundation of Jiangsu Province of China(BK2009104)Innovation Program of Graduated Student of Jiangsu Province China(CXZZ12-731,CXLX11-0388)
文摘The X80 pipeline steel was welded with the way of submerged arc welding. The SST （slow strain test） of the welded joint samples in the air, NACE （National Association of Corrosion Engineers） solution （no H2S）, NACE solution （saturated H2S） was performed to research the sensibility index of SCC （stress corrosion cracking） Iscc. The morphologies of the welded joint fractures and the fracture modes were observed with SEM （scanning electron microscope）, and the fracture chemical compositions were analyzed with EDS （energy dispersive spectrometer）, respectively. The fracture mechanisms of the welded joints were discussed. The results show that sensibility index of SCC in the air is not obvious, the fracture is dimple, and the mode of fracture is ductile fracture. The sensibility index of SCC in NACE solution （no H2S） is 13.21%, the stress corrosion is not obvious. The sample fracture shows quasi cleavage＋dimple, and the fracture mode is toughness＋brittle rupture. The sensibility index of SCC in NACE solution （saturated H2S） is 56.94%, the plastic loss is the most serious, appearing an obvious stress corrosion tendency, and there is no obvious necking phenomenon. The fracture mode is brittle fracture, and the sample fracture has a high sulfur concentration, prompting S to a aliquation of crisp crystal in the welded zone, and making its mechanical properties worsen.
