Alumina-forming austenitic stainless steels (AFA)  are designed for applications where corrosion and creep resistance are of paramount importance. However, they suffer from stress corrosion cracking and, due to their FCC crystalline structure, show poor resistance to volume swelling under irradiation. The motivation of our work is to take advantage of the knowledge acquired in the last 40 years of service of heat-resistance ferritic-martensitic steels , combined with the exceptional corrosion resistance properties offered by a protective layer of alumina. For this reason, in this research, alumina-forming martensitic steels have been designed. Extensive thermodynamic calculations have been performed under the approach proposed by Olson and Cohen where the stacking fault energy is estimated in order to optimize the martensitic transformation, coupled with the precipitation of strengthening MX precipitates. A compositional window with enough content of Cr and Al in order to obtain protective layers, but yet allowing the martensite formation, has been defined. The approach considers a single thermal treatment step (austenization + alumina forming) in order to make these alloys commercially viable.

Several alloys have been produced and characterized. The transformation from austenite to martensite has been evaluated using high resolution dilatometry, while the obtained microstructures and the capacity to form an alumina layer have been characterised using X-ray diffraction, optical and scanning electron microscopy. For a deeper characterisation of the alumina layer, scanning transmission electron microscopy, two-dimensional EDS maps (elemental mapping) as well as point and linear EDS were carried out to evaluate the distribution and proportion of elements in the alumina layer. The results presented pave the way to develop alumina forming martensitic steels for energy applications.