Development of low-activation martensitic stainless steels

Abstract

An evaluation has been made of the properties obtainable from elementally-substituted martensitic stainless steels, the objective being to achieve properties comparable with those of an established 12% CrMoVNb steel in a composition that would allow hands-on recycling after 100 y storage. Tungsten and increased contents of vanadium have been identified as alternative strengthening additions and their effects on the structure and properties of 0.15% C, 9 and 11% Cr steels have been studied. The closest approach to the reference steel was obtained with a composition of 11% Cr, 3% W and 0.24% V, which gave 0.1% proof strengths of 800 MPa and 490 MPa at room temperature and 550°C. In all the steels studied the principal precipitate at 675°C was M 23C 6 carbide. The Laves phase M 2W was formed in the 3% W steels overaged at 675°C and this, together with the relatively coarse prior austenite grain size, probably accounts for the comparatively low toughness in the overaged condition. It is concluded that 9 and 11% Cr, 1–3.0% W, 0.25–0.5% V steels form the basis for further development of low activity martensitic alloys.