EFFECTS OF ALLOYING ELEMENTS AND FOIL DIMENSIONS ON THE LIFE TIME OF THIN FE-CR-AL FOILS IN CATALYTIC CONVERTERS

摘要

Several parameters influencing the life cycle of Fe-20Cr-Al were investigated. For industrially used chemical compositions, the foil thickness of 50 microns is critical for applications in catalytic converters, since exponential scale growth due to surface aluminium depletion has to be considered. Oxidation resistance can also be increased by alloying with yttrium and hafnium as reactive elements. These are superior to those of cerium mischmetal or yttrium by alone. Overdoping can cause very high oxidation rates and severe internal oxidation and has to be avoided. Furthermore increasing the aluminium content is helpful as well. Since this may lead to embrittlement of conventionally produced materials, a new production technique was developed, which is based on aluminising of Fe-Cr at lower thickness. This techniques results in higher aluminium contents in near surface regions which are quite sufficient for increasing oxidation resistance.