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<p>The cyclic creep and oxidation behavior of 9Cr3W3Co steel were investigated in air and supercritical water (SCW) at 650&#xa0;°C under peak stresses of 185 ~ 215&#xa0;MPa. The results indicated that the lower the peak stress, the longer the oxidation time prior to fracture, and the thicker the oxide scale formed in SCW, leading to a more significant reduction in cyclic life and elongation of 9Cr3W3Co steel compared with those in air. As opposed to the thin, dense Cr-rich oxide layer that rapidly formed and suppressed further oxidation in air, oxygen rapidly diffused deep into the matrix along martensite block boundaries in SCW. Coupled with stress assistance, preferential oxidation along martensite block boundaries induced the formation of microcracks and voids. These defects aggravated surface oxidation and promoted crack propagation into the matrix, especially when martensite block boundaries were nearly perpendicular to the tensile stress direction, ultimately accelerating cyclic creep fracture and deteriorating ductility.</p>

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Cyclic creep degradation of 9Cr3W3Co martensitic steel associated with oxide scale cracking in supercritical water

  • 期刊论文

  • 发表日期：

    2026年6月3日

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  • H. G. Han,
  • Y. M. Han,
  • M. L. Wang,
  • Y. H. Lu,
  • C. G. Shang,
  • Z. Z. Chen

摘要

The cyclic creep and oxidation behavior of 9Cr3W3Co steel were investigated in air and supercritical water (SCW) at 650 °C under peak stresses of 185 ~ 215 MPa. The results indicated that the lower the peak stress, the longer the oxidation time prior to fracture, and the thicker the oxide scale formed in SCW, leading to a more significant reduction in cyclic life and elongation of 9Cr3W3Co steel compared with those in air. As opposed to the thin, dense Cr-rich oxide layer that rapidly formed and suppressed further oxidation in air, oxygen rapidly diffused deep into the matrix along martensite block boundaries in SCW. Coupled with stress assistance, preferential oxidation along martensite block boundaries induced the formation of microcracks and voids. These defects aggravated surface oxidation and promoted crack propagation into the matrix, especially when martensite block boundaries were nearly perpendicular to the tensile stress direction, ultimately accelerating cyclic creep fracture and deteriorating ductility.