Development of low-activation martensitic stainless steels

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 0.25% V, which gave 0.1% proof strengths of 800 MPa and 490 MPa at room temperature and 5500C. In all the steels studied the principal precipitate at 6750C was M23C6 carbide. The Laves phase M2W was formed in the 3% W steels overaged at 6750C 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. (orig.)