Microstructure and mechanical properties of newly developed low activation martensitic steels

The reference ferritic-martensitic steel of the European Fusion Technology Program, the 10CrMoNbV MANET cast, has been modified by replacing the elements that result in long term residual radioactivity when irradiated under a fusion neutron spectra by others which have shorter activation periods. A base composition of a 9CrWVTa steel has been so defined. Two different compositions of the base alloy have been cast from high purity components, in which the Mn and N contents have been varied. The extracted carbide types and their size distribution have been studied under the electron microscope. The mechanical properties of both compositions have been determined. Both steel compositions have a ductile-brittle transition temperature (DBTT) well below room temperature while their tensile properties are comparable to those of the parent (MANET) steel.