A potential new ferritic/martensitic steel for fusion applications

The A-21 steel is an Fe–Cr–Co–Ni–Mo–Ti–C steel that is strengthened by a fine distribution of titanium carbide (TiC) precipitates formed by thermomechanical treatment. Transmission electron microscopy of the A-21 reveals a high number density of small TiC particles uniformly distributed in the matrix. Below ≈600∘C, the strength of A-21 is less than the average value for conventional Cr–Mo or reduced-activation ferritic/martensitic steels. However, the strength is greater above 600°C. The Charpy impact properties of A-21 are comparable to those of the conventional and reduced-activation steels. Due to the fine TiC particles in the matrix, the creep-rupture properties of A-21 are superior to those of conventional Cr–Mo or reduced-activation Cr–W steels. Although the composition of the A-21 is not applicable for fusion because of the cobalt, the innovative production process may offer a route to an improved steel for fusion.