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Samples of AISI 304 and AISI 430 steels with dimensions of approximately 1.0 x 2.0 x 0.3 cm (width, length and thickness, respectively) were carefully polished to remove the original scale which was formed during the rolling process. The scales formed in a tubular furnace under dynamic synthetic air atmosphere with 3 ppm of humidity were analyzed by x ray diffraction and Mössbauer spectroscopy. In this work, the high temperature oxidation behavior of an austenitic stainless steel AISI 304 type is compared to the behavior of a ferritic stainless steel AISI 430. Knowledge of the initial oxidation behavior, hardness and adherence of the oxide formed on Fe-Cr alloys and stainless steels at higher temperatures at atmospheric pressure is important in processes such as annealing, acid pickling and cold working. They have advantage of lower costs than austenitic grades due to the absence of nickel, and also present lower expansion coefficient than austenitic steels, which is a great advantage when temperature cycling resistance is needed 1,2.Ī number of studies have been made on the initial oxidation of Fe-Cr alloys and the effect of oxygen partial pressure and of different atmospheres on the properties of the oxides, since the high-temperature oxidation resistance of these alloys depends on the oxide properties 2,7. Recently, ferritic stainless steels have been developed to substitute austenitic stainless steels in some applications, as automotive exhaust components, specially the upstream part of the exhaust line (manifold, down-pipe, converter shell), where temperatures can reach 1100 ☌. The AISI 304 austenitic steels are widely used in chemical, petrochemical and pharmaceutical industries. Keywords: AISI 304 and AISI 430 stainless steel, oxidation, Mössbauer spectroscopyĪustenitic stainless steels are very corrosion resistant in a wide range of corrosive media and they can be used in a wide range of temperatures, from cryogenic conditions up to about 1150 ☌. The activation energy for oxidation is smaller for AISI 430 steel in relation to AISI 304 steel in the range of studied temperatures, and therefore the AISI 430 steel is less resistant towards oxidation at high temperatures. Hematite was found to be the dominant oxide at lower temperatures, whereas magnetite preferentially forms at higher temperatures. The main crystalline phases found in the oxidized materials at temperatures above 1100 ☌ were hematite and magnetite for AISI 430 steel, and hematite and a spinel-like phase for AISI 304 steel. Mössbauer spectroscopy and x ray diffraction were used to access the phase composition of the formed scales. The oxidation behavior of AISI 304 and AISI 430 stainless steels was investigated from 1100 ☌ up to 1200 ☌. IIIACESITA S.A., 35180-018 Timóteo - MG, Brazil
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IIDepartamento de Física, Redemat, Universidade Federal de Ouro Preto, 35400 Ouro Preto - MG, Brazil
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IDepartamento de Química, Universidade Federal de Ouro Preto, Campus Universitário - Morro do Cruzeiro, 35400 Ouro Preto - MG, Brazil High temperature oxidation behavior of AISI 304 and AISI 430 stainless steelsĬarlos Eduardo Reis de Carvalho I Geraldo Magela da CostaI, * André Barros Cota II Edson Hugo Rossi III