The Evolution of Precipitates in a Novel Heat-Resistant Martensitic Steel During Creep

In the past decades, several 9-12 wt% Cr-containing martensitic steels have been researched for the application in ultra-supercritical power plants at 650 degrees C, which is still a worldwide challenge. Among them, G115 martensitic steel, which was developed in China, is one of promising candidates. It has the basic composition of 9% Cr-3% W-3% Co and contains 1% Cu (all in wt%) and the optimized contents of B and N, leading to much better creep strength and creep ductility than P92 steel. Both M23C6 carbides and e-Cu particles were found during the tempering of G115 steel, and the former have finer size than those in P92 steel, which results in Laves phase to form with the refined size too during the latter creep stage. All these formed precipitates shall contribute to improved creep rupture strength of G115 steel.