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<p>The microstructural evolution and carbon diffusion behavior of 25Cr35NiNb alloy under various creep stresses and carburization conditions were systematically investigated. The results indicate that creep triggers the transformation of M<sub>7</sub>C<sub>3</sub> and NbC into M<sub>23</sub>C<sub>6</sub> and G phase, respectively, accompanied by secondary carbide precipitation. Both extended creep duration and elevated stress levels facilitate precipitate coarsening. Continuous creep exposure gives rise to the stabilization of M<sub>23</sub>C<sub>6</sub> content at 7% but accelerates G phase accumulation, though growth rates of both phases progressively decrease over time. Cavity evolution exhibits contrasting trends, with the area fraction increasing continuously while cavity density declines significantly with prolonged creep. Carburization induces three notable effects: regeneration of initial M<sub>7</sub>C<sub>3</sub> and NbC, accelerated precipitate coarsening, and graphite formation. Depth-dependent carbon profiles consistently show an initial peak followed by gradual decay, with surface carbon concentration decreasing and carburization depth increasing to exceed 600&#xa0;μm as the creep strain accumulates. Notably, the protective Cr<sub>2</sub>O<sub>3</sub> scale demonstrates partial effectiveness in hindering carbon ingress.</p>

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Evolution of Creep Damage and its Effect on the Carburization Behavior of Centrifugally Cast 25Cr35NiNb Alloy

  • 期刊论文

  • 发表日期：

    2025年3月27日

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  • Chengming Fuyang,
  • Jianming Gong,
  • Heng Li,
  • Jinduo Liu,
  • Wei Yan,
  • Jiabao Pan,
  • Xiaofeng Guo

摘要

The microstructural evolution and carbon diffusion behavior of 25Cr35NiNb alloy under various creep stresses and carburization conditions were systematically investigated. The results indicate that creep triggers the transformation of M7C3 and NbC into M23C6 and G phase, respectively, accompanied by secondary carbide precipitation. Both extended creep duration and elevated stress levels facilitate precipitate coarsening. Continuous creep exposure gives rise to the stabilization of M23C6 content at 7% but accelerates G phase accumulation, though growth rates of both phases progressively decrease over time. Cavity evolution exhibits contrasting trends, with the area fraction increasing continuously while cavity density declines significantly with prolonged creep. Carburization induces three notable effects: regeneration of initial M7C3 and NbC, accelerated precipitate coarsening, and graphite formation. Depth-dependent carbon profiles consistently show an initial peak followed by gradual decay, with surface carbon concentration decreasing and carburization depth increasing to exceed 600 μm as the creep strain accumulates. Notably, the protective Cr2O3 scale demonstrates partial effectiveness in hindering carbon ingress.