Influence of tantalum and nitrogen contents, normalizing condition and TMCP process on the mechanical properties of low-activation 9Cr–2W–0.2V–Ta steels for fusion application

Abstract

For clarifying the reason of good creep and mechanical properties and improving the mechanical properties of the low-activation 9Cr–2W–0.2V–Ta steels (JLF-1 steels), the influence of Ta, N contents, normalizing condition and thermo-mechanical controlled processes (TMCP) on the mechanical properties of the 9Cr–2W–0.2V–Ta steels was investigated in contrast with conventional 9Cr–1Mo–0.2V–Nb steels. The creep strength of the 9Cr–2W–0.2V–Ta steels increases with increasing amount of Ta and N contents irrespective of the manufacturing processes. An increase in the normalizing temperature or the application of TMCP processes can also improve creep strength. It is hypothesized that the increase in creep strength due to an increase in normalizing temperature or the application of TMCP processes is attributed to the uniform distribution of fine (Ta,V)(C,N) precipitates. Furthermore, the 9Cr–2W–0.2V–Ta steels demonstrate good toughness mainly due to a fine austenite grain size. The 9Cr–2W–0.2V–Ta steels have equivalent or better creep strength and better toughness compared with 9Cr–1Mo–0.2V–Nb steels.