Effect of Al on microstructure and oxidation resistance of Fe-20Cr-35Ni-0.6Nb alloy

doi:10.13251/j.issn.0254-6051.2022.12.024

Abstract

Abstract: Oxidation resistance behaviors of Fe-25Cr-35Ni-0.6Nb-xAl (x=0.5%, 1.5%, 2.5%, mass fraction) Nb-containing alloys at 1000 ℃ in air were investigated by mass gain method. The microstructure and oxide scales of the alloys were observed and analyzed by SEM, EDS, TEM and Raman spectroscopy. The results show that the microstructure of the three Nb-containing alloys is single-phase austenite, and a small amount of NbC precipitated phases are dispersed in the matrix. The content of precipitated phase and the grain size remain unchanged before and after oxidation. With the addition of 0.5% and 1.5% Al, a multilayer oxide film forms on the surface of the Nb-containing alloys, of which the first and third layers are Cr₂O₃, the subsurface layer is mainly composed of NiCr₂O₄, NiFe₂O₄ and Fe₂O₃, and the innermost layer is Al₂O₃ internal oxide. In addition, the porosity of the oxide film is aggravated by NbC precipitates in the matrix and a small amount of Nb oxides (Nb₂O₅) in the oxide film. When the Al content increases to 2.5%, a continuous and dense Al₂O₃ oxide film forms on the surface of Fe-25Cr-35Ni-0.6Nb alloy, which reduces the oxidation rate and improves the oxidation resistance of the alloy.

Key words: Fe-20Cr-35Ni-0.6Nb alloy, Al, NbC, Al₂O₃ oxide film, high-temperature oxidation resistance

CLC Number:

TG142.1

Xu Wanjian, Jia Guodong, Yang Chunli, Wang Zixie, Pan Jie, Xiao Xueshan. Effect of Al on microstructure and oxidation resistance of Fe-20Cr-35Ni-0.6Nb alloy[J]. Heat Treatment of Metals, 2022, 47(12): 138-145.

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