Design of alumina-forming austenitic stainless steel using genetic algorithms

Alumina-forming austenitic stainless steels (AFA-SSs) are candidates for high temperature applications to replace conventional stainless steels that form unstable chromium-oxide. In this work, a new AFA-SS composition was designed, through thermodynamic considerations, oxidation model calculations, and Genetic Algorithm-based optimization, which is expected to form alumina scale with only few number of alloying additions. The model incorporates thermodynamic stability of alumina with the kinetics of diffusion of aluminum and oxygen, and then considers the role of chromium as the third element, to predict alumina scale formability. In the present study, this model was utilized to design a new AFA-SS with minimum number of alloying additions. In addition, the oxidation behavior of the designed alloy was investigated at 800 °C to demonstrate its alumina forming capability and compared with a well-known alumina-forming steel. The cross-sections of the scales were studied using scanning electron microscopy and energy dispersive spectroscopy. The results confirmed the formation of the alumina layer in the designed alloy and validated the utility of the model and Genetic Algorithm-based optimization.