Design and high temperature behavior of novel heat resistant steels strengthened by high density of stable nanoprecipitates

Abstract

International efforts have been focused on the development of new 9Cr Ferritic/Martensitic steels capable of operating at temperatures above 700 °C to improve thermal efficiency of new power plants. The distribution and size of the MX nanoprecipitates present in these steels have been reported to be the key factor for improving the thermal stability of the microstructure during creep. Bearing in mind these findings, three different heat resistant steels were designed to have a higher number density of MX nanoprecipitates than commercial 9Cr Ferritic/Martensitic steels. The manufacturing and subsequent microstructural characterization carried out showed that this goal was achieved. Preliminary high temperature strength results performed by means of Small Punch Creep Tests (SPCT) demonstrated that these new steels improve significantly the high temperature strength without an important loss of ductility as compared to a current commercial 9Cr Ferritic/Martensitic steel.