Investigation of Microstructure and Mechanical Properties of Ferritic/Martensitic Steels Used in Fission and Fusion Reactors

A dramatic increase in the world-wide demand for energy requires to design nuclear reactors with high efficiency. The requirement for a high efficiency reactor necessitates using high pressure and high temperature designs. Because of the high temperature operation in the new generation of nuclear power reactors, ferritic/martensitic steel is unanimously considered to be the most suitable metal for the reactor design. In this research, by melting in a induced furnace, ferritic/martensitic steel was produced and then the micro-structures of the sed were investigated by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical properties of these types of steel at different temperatures were investigated with the tensile and impact tests. The fractography investigation has also been conducted with the SEM. The results showed that in the As-cast form, the structure involves binate ferrites that after the heat treatment change to the martensitic structure. The maximum hardness was obtained in the quenched and normalized conditions. The mechanical properties in the NT form are better than the QT form. The ductility in these types of steel reduces by increasing temperature up to 400˚C, and then it improves by increasing the temperature.