Research progress on high temperature materials for 700°C ultra-supercritical coal-fired units

Abstract

Nowadays, material research worldwide for 700°C ultra-supercritical firepower generator units (USC-FPGUs) is focus on the evolution of microstructures and mechanical properties as well as the research progress of high-temperature materials, which are used for fabricating water-cooled wall, superheater/reheater tube, main steam pipe and high-temperature steam header. HCM12 steel and Inconel 617 alloy are suited for high-temperature segment of water-cooled wall. Inconel 740H alloy developed from Inconel 740 alloy after modification is the preferred material for superheater/reheater, main steam pipe and high-temperature steam header due to its excellent persistent creep strength and welding performance. In future research, it is necessary to further verify the high-temperature persistent strength and creep strength of the aforementioned materials through practice. Meanwhile, the optimum hot working process should be exploited to improve the hot-workability and welding performance as well as reduce the cost of materials.