Advanced materials for structural components of Indian sodium-cooled fast reactors

Creep strength enhancement of modified 9Cr-1Mo steel and its fusion welded joint has been addressed through microalloying the steel with boron along with the restriction on nitrogen content. The microalloying not only improves the creep strength of the steel also reduces the type IV cracking susceptibility of the fusion welded joint of the steel. The optimum contents of boron and nitrogen in the steel have been identified as around 60 ppm boron and 100 ppm nitrogen for better creep strength and type IV cracking resistance. The paper describes the challenges in developing the materials.