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<p>NiCo-based alloys are widely recognized as superior high-temperature self-lubricating materials. Nevertheless, they are prone to failure due to severe oxidation, and the research on solving this issue remains insufficient. In the present work, simple model Ni20Cr–xCo–3Al (wt%) alloys were fabricated by using mechanical alloying (MA) and spark plasma sintering (SPS), and their isothermal and cyclic oxidation behavior at 800&#xa0;°C in air for 100&#xa0;h was investigated. Results show that, as the Co content increases, the alloys presented a microstructural change from coarse grain to heterogeneous structure with ultrafine grains surrounding the coarse ones. The alloy containing 30&#xa0;wt% of Co successfully formed a thinner, flatter, denser and more intact external α-Al<sub>2</sub>O<sub>3</sub> scale in both isothermal and cyclic oxidation, exhibiting remarkable oxidation resistance compared with the other alloys. This arises from the favorable balance between elemental diffusion and oxidation, attributed to its heterogeneous structure.</p>

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Effect of Co Content on Microstructure and Oxidation Behavior of Ni20Cr–xCo–3Al Alloys Prepared by Spark Plasma Sintering

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Chengji Liu,
  • Minghui Chen,
  • Shasha Yang,
  • Fuhui Wang

摘要

NiCo-based alloys are widely recognized as superior high-temperature self-lubricating materials. Nevertheless, they are prone to failure due to severe oxidation, and the research on solving this issue remains insufficient. In the present work, simple model Ni20Cr–xCo–3Al (wt%) alloys were fabricated by using mechanical alloying (MA) and spark plasma sintering (SPS), and their isothermal and cyclic oxidation behavior at 800 °C in air for 100 h was investigated. Results show that, as the Co content increases, the alloys presented a microstructural change from coarse grain to heterogeneous structure with ultrafine grains surrounding the coarse ones. The alloy containing 30 wt% of Co successfully formed a thinner, flatter, denser and more intact external α-Al2O3 scale in both isothermal and cyclic oxidation, exhibiting remarkable oxidation resistance compared with the other alloys. This arises from the favorable balance between elemental diffusion and oxidation, attributed to its heterogeneous structure.