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<p>To satisfy the requirements for high-temperature and long-term service of carbide-strengthened 25Cr35NiNb alloys in the petrochemical industry, the effects of C addition (0.2 ~ 0.6 wt pct) on microstructural evolution and creep behavior were systematically investigated at 1173&#xa0;K (900&#xa0;°C) and 1323&#xa0;K (1050&#xa0;°C). Increasing C content significantly promoted the formation of Cr-rich carbides rather than Nb-rich carbides, while simultaneously suppressing the precipitation of the G phase. Multistep tensile creep tests revealed a pronounced enhancement in creep resistance with increasing C addition. The high apparent stress exponent and activation energy associated with power-law creep were rationalized by introducing a threshold stress, which originated from multiscale precipitation strengthening involving nanosized MC and sub-micron M<sub>23</sub>C<sub>6</sub> carbides. The increase in threshold stress with C addition was mainly attributed to secondary M<sub>23</sub>C<sub>6</sub> precipitates, which facilitated general dislocation climb and introduced additional back stress through sub-grain boundary impediment. Owing to the analogous creep-controlling mechanisms, the steady-state creep behavior can be reliably predicted over a wide range of C contents, applied stresses, and temperatures. This study provides fundamental insight into composition- and temperature-dependent microstructural evolution and offers guidance for the design of heat-resistant alloys operating above 1273&#xa0;K (1000&#xa0;°C).</p>

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Effect of Carbon Content on the Creep Threshold Stress and Deformation Mechanism of 25Cr35NiNb Alloys at Elevated Temperatures

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • Shulin Xiang,
  • Tengfei Cheng,
  • Xiaotian Fang,
  • Wensheng Zhu,
  • Jinghua Jiang,
  • Dan Song

摘要

To satisfy the requirements for high-temperature and long-term service of carbide-strengthened 25Cr35NiNb alloys in the petrochemical industry, the effects of C addition (0.2 ~ 0.6 wt pct) on microstructural evolution and creep behavior were systematically investigated at 1173 K (900 °C) and 1323 K (1050 °C). Increasing C content significantly promoted the formation of Cr-rich carbides rather than Nb-rich carbides, while simultaneously suppressing the precipitation of the G phase. Multistep tensile creep tests revealed a pronounced enhancement in creep resistance with increasing C addition. The high apparent stress exponent and activation energy associated with power-law creep were rationalized by introducing a threshold stress, which originated from multiscale precipitation strengthening involving nanosized MC and sub-micron M23C6 carbides. The increase in threshold stress with C addition was mainly attributed to secondary M23C6 precipitates, which facilitated general dislocation climb and introduced additional back stress through sub-grain boundary impediment. Owing to the analogous creep-controlling mechanisms, the steady-state creep behavior can be reliably predicted over a wide range of C contents, applied stresses, and temperatures. This study provides fundamental insight into composition- and temperature-dependent microstructural evolution and offers guidance for the design of heat-resistant alloys operating above 1273 K (1000 °C).