Production of aluminium coated ferritic stainless steel by co-rolling and annealing

Ferritic stainless steel enriched with aluminium (>7%) represents the best material for the production of substrates in catalytic converters because of its good corrosion resistance at high temperature (700-1000°C). Enriching steel surface with aluminium avoids brittleness problems related to the traditional metallurgical process and, due to the high superficial aluminium concentration, enhances the Al2O3, scale formation in the early stages of the oxidation process. Among several techniques, the co-rolling process appears to be a promising technology for enriching ferritic stainless steel surface with aluminium. That versatile technology produces, at room temperature, a very adherent aluminium coating without affecting the structural and mechanical properties of the substrate. In this work annealed AISI 430 ferritic stainless steel has been cold rolled together with aluminium foil to form an Al-steel-Al sandwich. The aim of the work was to enhance the oxidation resistance through a controlled oxidation of a thin aluminium layer. The diffusion bonding obtained via an annealing treatment was evaluated studying the concentration profiles as a function of process temperature. Intermetallics and/or solid solutions formed were characterized by X-Ray Diffraction (XRD).