ISSN 2594-5327
59º Congresso anual — Vol. 59 , num. 1 (2004)
Título
Autoria
DOI
Downloads
Resumo
Generally, oxide scales formed on high Cr steels are multi-layered and the kinetics are strongly influenced by the alloy grain boundaries. In the present study, the oxidation behaviour of an austenitic steel TP347 with different grain sizes was studied to identify the role of grain-boundaries in the oxidation process. Heat treatment in an inert gas atmosphere at 1050ºC was applied to modify the grain size of the steel TP347. The mass gain during subsequent oxidation was measured using a microbalance with a resolution of 10⁻⁵ g. The scale morphology was examined using SEM in combination with energy-dispersive X-ray spectroscopy (EDS). Oxidation of TP347 with a grain size of 4 µm at 750ºC in air follows a parabolic rate law. For a larger grain size (65 µm), complex kinetics is observed with a fast initial oxidation followed by several different parabolic oxidation stages. SEM examinations indicated that the scale formed on specimens with smaller grain size was predominantly Cr₂O₃, with some FeCr₂O₄ at localized sites. For specimens with larger grain size the main oxide is iron oxide. It can be concluded that protective Cr₂O₃ formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.
Generally, oxide scales formed on high Cr steels are multi-layered and the kinetics are strongly influenced by the alloy grain boundaries. In the present study, the oxidation behaviour of an austenitic steel TP347 with different grain sizes was studied to identify the role of grain-boundaries in the oxidation process. Heat treatment in an inert gas atmosphere at 1050ºC was applied to modify the grain size of the steel TP347. The mass gain during subsequent oxidation was measured using a microbalance with a resolution of 10⁻⁵ g. The scale morphology was examined using SEM in combination with energy-dispersive X-ray spectroscopy (EDS). Oxidation of TP347 with a grain size of 4 µm at 750ºC in air follows a parabolic rate law. For a larger grain size (65 µm), complex kinetics is observed with a fast initial oxidation followed by several different parabolic oxidation stages. SEM examinations indicated that the scale formed on specimens with smaller grain size was predominantly Cr₂O₃, with some FeCr₂O₄ at localized sites. For specimens with larger grain size the main oxide is iron oxide. It can be concluded that protective Cr₂O₃ formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.
Palavras-chave
austenitic steel, Cr₂O₃ formation, grain boundary diffusion, high-temperature oxidation
austenitic steel, Cr₂O₃ formation, grain boundary diffusion, high-temperature oxidation
Como citar
Trindade, Vicente Braz; Krupp, Ulrich; Yang, Songlan; Christ, HansJürgen.
Effect of Alloy Grain Size on the High-Temperature Oxidation Behaviour of the Austenitic Steel TP 347,
p. 3112-3119.
In: 59º Congresso anual,
São Paulo, Brasil,
2004.
ISSN: 2594-5327, DOI 10.5151/2594-5327-4122
