Cyclic oxidation behavior of co-rolled al-ferritic stainless steel

The lifetime of thin-walled catalyst-carrying foils Is directly linked to the overall amount of aluminum present in the base alloy. Ferritic stainless steel containing more than 7 wt. % of Al represents an interesting material for the production of substrates in catalytic converters because of its good corrosion resistance at high temperature. Despite that, the considerable brittleness of the alloy makes production by means of traditional metallurgical processes difficult. Enriching the steel surface with aluminum avoids these problems and due to the high superficial aluminum concentration, enhances the Al 2O 3 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 surfaces with aluminum without affecting the structural and mechanical properties of the substrate. This process involves cold rolling the annealed AISI 430 ferritic stainless steel together with aluminum foil to form an Al-steel-Al sandwich. After a preoxidation treatment the resultant assemblies were subjected to cyclic oxidation in air. Their oxidation behavior was then characterized by the weight gain versus the number of cycle curves. Oxides were examined by SEM and the phases were identified by X-ray diffraction (XRD). The results highlight that in the lower range of temperatures (T<900°C) the oxide layer appears to be very adherent, even after 1000 cycles. While at temperatures higher than 900°C, the scale is characterized by convolutions and spalls off after a few hundred cycles. Copyright © 2007 by ASTM International.