EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Heat resistant steels demand microstructures that remain stable under high-temperature conditions. Security and thermal efficiency are key factors for future nuclear reactors, for this reason, improved materials have to be researched and developed. ODS ferritic alloys exhibit an excellent mechanical behavior under strong irradiation and high working temperatures, making them suitable for applications in the nuclear industry. However, existing ODS steels need a good balance between their UTS and toughness, so new strategies to solve this requirement have to be investigated. The first step in microstructural design is to understand the reinforcement mechanisms and identify those that play a major role. Thus, the composition of different ferritic steels has been modified by conditioning the dispersion of nano-oxides depending on the forming elements present (Zr, Ti, Y) or by conditioning grain growth using the incorporation of boron. Two of the most determinant contributions to the material's mechanical behavior are associated with the precipitate density and the dislocation density. Thanks to TEM and X-ray diffraction observations, it has been possible to measure them to define the key features in the response of the ferritic stainless steels developed in this work. The creep resistance has been studied by means of the small punch creep test (SPCT) at a constant temperature, modifying the load from 250 to 300 N to obtain the power law that could explain its behavior. To know the influence of the alloy systems, the response of 4 different compositions has been considered. Thus, a complete characterization of the microstructures achieved before and after SPCT has been carried out, including SEM, TEM, or EBSD among other tests.