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<p>The high-temperature oxidation behavior and mechanisms of as-cast and cold-rolled (20%CR and 60%CR) alumina-forming austenitic (AFA) steels were investigated in dry air at 800&#xa0;°C. The phase composition, morphology, microstructure, element distribution, and oxidation kinetics of the oxidized steels were systematically characterized. The results indicate that the mass gains of both as-cast and cold-rolled samples increase rapidly during the first 100&#xa0;h of exposure. During prolonged oxidation, the mass gains of as-cast and 60%CR samples increase gradually, while the mass gain of 20%CR AFA steel fluctuates significantly. The oxide layer comprises an outer oxide layer rich in (Fe,Cr) oxides and an inner Al<sub>2</sub>O<sub>3</sub>-dominated layer. The reduced oxidation resistance of the 20%CR sample is attributed to lower dislocation density, which cannot provide sufficient nucleation sites for the B2-NiAl phase, resulting in a lack of a continuous supply of Al for the formation of a dense and continuous Al<sub>2</sub>O<sub>3</sub> protective film. Conversely, the improved oxidation resistance of the 60%CR sample arises from the formation of δ-ferrite and precipitated B2-NiAl phases, facilitating the rapid development of a continuous Al<sub>2</sub>O<sub>3</sub> film on the surface. Overall, both as-cast and cold-rolled AFA steels demonstrate excellent oxidation resistance at 800&#xa0;°C.</p>

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High-Temperature Oxidation Behavior of the As-Cast and Cold-Rolled Alumina-Forming Austenitic Steels at 800 °C

  • 期刊论文

  • 发表日期：

    2025年9月9日

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  • Ke Zhu,
  • Fujian Zhang,
  • Shixin Xu,
  • Zhimin Zhang,
  • Ke Feng,
  • Ning Guo

摘要

The high-temperature oxidation behavior and mechanisms of as-cast and cold-rolled (20%CR and 60%CR) alumina-forming austenitic (AFA) steels were investigated in dry air at 800 °C. The phase composition, morphology, microstructure, element distribution, and oxidation kinetics of the oxidized steels were systematically characterized. The results indicate that the mass gains of both as-cast and cold-rolled samples increase rapidly during the first 100 h of exposure. During prolonged oxidation, the mass gains of as-cast and 60%CR samples increase gradually, while the mass gain of 20%CR AFA steel fluctuates significantly. The oxide layer comprises an outer oxide layer rich in (Fe,Cr) oxides and an inner Al2O3-dominated layer. The reduced oxidation resistance of the 20%CR sample is attributed to lower dislocation density, which cannot provide sufficient nucleation sites for the B2-NiAl phase, resulting in a lack of a continuous supply of Al for the formation of a dense and continuous Al2O3 protective film. Conversely, the improved oxidation resistance of the 60%CR sample arises from the formation of δ-ferrite and precipitated B2-NiAl phases, facilitating the rapid development of a continuous Al2O3 film on the surface. Overall, both as-cast and cold-rolled AFA steels demonstrate excellent oxidation resistance at 800 °C.