Investigation of Developed Ferritic and Martensitic Stainless Steels for Nuclear Power Reactors

Abstract

Aluminium, tungsten and aluminium – tungsten ferritic stainless-steel alloys were developed and produced using a 30 kg pilot plant induction furnace of medium frequency at the same conditions to be applied in nuclear reactor shielding material. Precipitation hardening strengthening technique with two different mechanisms M7C3, and Fe2W laves was studied in ferritic stainless steel. The investigation was achieved by using optical and scanning electron microscope observations to monitor either the chemical composition or the morphology of the secondary phases. In addition, XRD was used to identify the change in constituent phases, accompanying the heat treatment process. Mechanical properties and strain hardening character of the steel were determined. It was found that morphology of W-base laves is coarse, and nucleated at the high ferrite angle boundary. This provides much stability for ferrite boundaries, enhancing the strength of the matrix with free effect on ductility. On contrary, M7C3 secondary phase has a significant deterioration effect on the ductility of ferrite stainless steel, in opposite to its effect on enhancing yield and ultimate strength. Higher hardness, ultimate strength, and ultimate tensile strength appeared in the developed alloys. Aluminium stainless-steel elongation had lower values. The results of corrosion test showed that modified stainless steel with aluminium and tungsten (FS11) has the highest corrosion resistance among all investigated steels. Finally, total slow neutrons, neutrons > 10 keV, and slow neutrons of aluminium-tungsten based ferritic stainless-steel alloys which carried out using 241Am-Be neutron source as well as a wide range up to 1400 keV energies of gamma rays, which emitted from Co-60, Cs-137 and Eu-152, were used by means of NaI (Tl) detector and studied using the XCOM program. Results showed that all studied stainless-steel alloys own a converge values of neutron macroscopic cross sections (Σ, cm-1). Moreover, there is no significant variation of the value of mass attenuation coefficients (σ, cm2/g) for the studied alloys. Good agreement between both experimental and calculated results of mass attenuation coefficients was achieved. A new composition for several nuclear applications such as, nuclear shielding applications were achieved.