Effects of metallurgical chemistry and service conditions on the oxidation limited life time of FeCrAl-based components
FeCrAl alloys are high temperature structural materials with ever increasing technological importance, because in the temperature range of 900-1300°C their resistance against environmental attack exceeds that of other metallic materials. This is due to the formation of a protective alumina scale on the surface of FeCrAl-alloys during high temperature service. During exposure at elevated temperatures, the major life limiting factor for FeCrAl alloys is the depletion of the alloy Al-content. In the present work a number of commercial and model alloys have been studied with respect to the lifetime oxidation behaviour. The experimentally determined lifetimes were compared with those calculated based on the available lifetime prediction model. Analytical studies were performed on oxidised alloys using a range of surface analysis techniques to elucidate the oxidation mechanisms as a function of exposure time and temperature. The results demonstrate the importance of the minor alloying chemistry for scale growth rate and adherence and consequently for the service life of FeCrAl-based components. The observed differences in oxidation rates between the studied commercial materials and even between different batches of one commercial alloy have been found to originate from the interaction of typical minor alloying additions of the reactive elements, such as Y, La, Ti, Zr and Hf with typical alloy impurities of carbon and nitrogen. A major finding was that for this reason, the optimum oxidation resistance can not be achieved by one reactive element addition, but rather by a combination of the latter. The exact amounts, type and distribution of the reactive elements must be carefully selected depending on the particular alloy application.
info:eu-repo/classification/ddc/660, Technische Chemie, Eisenlegierung, Chromlegierung, Aluminiumlegierung, Korrosionsbeständigkeit, Hochtemperaturkorrosion, Oxidation, Lebensdauer, Legierungselement
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