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<p>Austempered ductile iron (ADI) is a widely used material, and many fields of the automotive industry benefit from its superior mechanical properties. Nevertheless, its application can be largely expanded if improvements in corrosion and high-temperature resistance are achieved. This study investigates the high-temperature oxidation behavior of ADI substrates aluminized with pure Al and aluminum-chromium (AlCr) slurry coatings. The specimens were subjected to oxidation at 650 and 700&#xa0;°C for up to 2000 h in air, with periodic weight change measurements and microstructural analyses conducted to evaluate their performance. The results demonstrate that surface aluminization significantly improves the oxidation resistance of ADI, with mass change reductions by factors of 13.7 and 3.4 for pure Al slurry-coated specimens and 4.7 and 2.6 for AlCr-coated specimens at 650 and 700&#xa0;°C, respectively. The localized Fe<sub>2</sub>O<sub>3</sub> growth was observed through microdefects and uncoated regions within the IDZ right above the graphite inclusions. The slurry coatings of AlCr formed thinner IDZ and exhibited good adherence to the substrate, suppressing the material’s oxidation more effectively. At 700&#xa0;°C, increased mobility of iron and oxygen ions facilitated the growth of Fe<sub>2</sub>O<sub>3</sub> mounds that incorporated chromium oxide particles from the overlay slurry coating, thereby enhancing its adhesion.</p>

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Oxide Scale Evolution on Al- and AlCr- Slurry-Coated Deformable Austempered Ductile Iron After Long-Term Exposure at 650 and 700 °C

  • 期刊论文

  • 发表日期：

    2025年9月24日

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  • Olga Tsurtsumia,
  • Lili Nadaraia,
  • Levan Khundadze,
  • Elguja Kutelia,
  • Tengiz Kukava

摘要

Austempered ductile iron (ADI) is a widely used material, and many fields of the automotive industry benefit from its superior mechanical properties. Nevertheless, its application can be largely expanded if improvements in corrosion and high-temperature resistance are achieved. This study investigates the high-temperature oxidation behavior of ADI substrates aluminized with pure Al and aluminum-chromium (AlCr) slurry coatings. The specimens were subjected to oxidation at 650 and 700 °C for up to 2000 h in air, with periodic weight change measurements and microstructural analyses conducted to evaluate their performance. The results demonstrate that surface aluminization significantly improves the oxidation resistance of ADI, with mass change reductions by factors of 13.7 and 3.4 for pure Al slurry-coated specimens and 4.7 and 2.6 for AlCr-coated specimens at 650 and 700 °C, respectively. The localized Fe2O3 growth was observed through microdefects and uncoated regions within the IDZ right above the graphite inclusions. The slurry coatings of AlCr formed thinner IDZ and exhibited good adherence to the substrate, suppressing the material’s oxidation more effectively. At 700 °C, increased mobility of iron and oxygen ions facilitated the growth of Fe2O3 mounds that incorporated chromium oxide particles from the overlay slurry coating, thereby enhancing its adhesion.