Superalloys and the development of advanced ultra-supercritical power plants

A 700 degrees C advanced ultra-supercritical (A-USC) power plant technology project was initiated in China in the year of 2011. The highest temperature components in A-USC boiler are superheater and reheater tubes. The fire-side metal temperature can reach 750 degrees C (even higher). Based on the very long time service(30-40 years) these important high temperature tubes require 10(5)h long time stress rupture strength higher than 100MPa and the corrosion/oxidation layer loss less than 2mm for 2x10(5)h. The highest temperature components in 700 degrees C steam turbine are the buckets of different stages and require very long service time. At this severe condition only superalloys can fulfill these unusual requirements. This paper reviewed Fe-Ni and Ni-base superalloys from the view point of structure stability and long term mechanical properties and corrosion/oxidation resistance for 700 degrees C A-USC power plant materials selection.