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<p>To clarify the effect of post-heat treatment on the stress corrosion cracking (SCC) behavior of spring-grade Inconel 718 in reactor environments, two Alloy 718 conditions with the same nominal chemical composition and sampled from the same location of the same plate were compared under simulated PWR primary-water conditions. 718#1 was used as the blank control, while 718#2 was produced from the control material by stress-relief annealing at 900&#xa0;°C for 1&#xa0;h followed by air cooling and a subsequent re-aging treatment at 720&#xa0;°C for 8&#xa0;h, furnace cooled to 620&#xa0;°C and held such that the total aging time was 18&#xa0;h, followed by air cooling. Miniature compact-tension specimens were tested at 360&#xa0;°C and 19.6&#xa0;MPa in 1000 ppm B + 3.5 ppm Li water using constant-K loading, and crack growth was monitored in situ by the direct current potential drop method. The crack path and crack-tip region were characterized by SEM/BSE, EBSD, TEM-EDS, and TKD. At K = 38.5 MPa&#xa0;m<sup>1/2</sup>, the heat-treated 718#2 exhibited a lower steady crack growth rate (4.3 × 10<sup>−7</sup> mm s<sup>−1</sup>) than the control 718#1 (6.6 × 10<sup>−7</sup> mm s<sup>−1</sup>). Both materials changed from transgranular cracking during pre-cracking/transition to intergranular propagation under sustained loading, accompanied by secondary intergranular cracks. The improved SCC resistance of 718#2 is attributed primarily to the reduction in continuous grain-boundary δ-phase precipitation and residual strain, together with a finer and more homogeneous grain structure, which collectively suppress local strain concentration and intergranular crack advance.</p>

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Effect of Heat Treatment on Stress Corrosion Crack Growth of Inconel 718 in Simulated PWR Primary Water

  • 期刊论文

  • 发表日期：

    2026年6月25日

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  • Lu Chen,
  • Fuliang Chen,
  • Xiaoqiang Chen,
  • Yahua Qiao,
  • Man Zhang,
  • Hanfang Xie,
  • Xiangyang Chen,
  • Linyue Pan,
  • Xintao Zhang,
  • Chen Wang,
  • Yanguang Cui,
  • Junqiang Lu,
  • You Wang,
  • Jiamei Wang,
  • Liang Wang

摘要

To clarify the effect of post-heat treatment on the stress corrosion cracking (SCC) behavior of spring-grade Inconel 718 in reactor environments, two Alloy 718 conditions with the same nominal chemical composition and sampled from the same location of the same plate were compared under simulated PWR primary-water conditions. 718#1 was used as the blank control, while 718#2 was produced from the control material by stress-relief annealing at 900 °C for 1 h followed by air cooling and a subsequent re-aging treatment at 720 °C for 8 h, furnace cooled to 620 °C and held such that the total aging time was 18 h, followed by air cooling. Miniature compact-tension specimens were tested at 360 °C and 19.6 MPa in 1000 ppm B + 3.5 ppm Li water using constant-K loading, and crack growth was monitored in situ by the direct current potential drop method. The crack path and crack-tip region were characterized by SEM/BSE, EBSD, TEM-EDS, and TKD. At K = 38.5 MPa m1/2, the heat-treated 718#2 exhibited a lower steady crack growth rate (4.3 × 10−7 mm s−1) than the control 718#1 (6.6 × 10−7 mm s−1). Both materials changed from transgranular cracking during pre-cracking/transition to intergranular propagation under sustained loading, accompanied by secondary intergranular cracks. The improved SCC resistance of 718#2 is attributed primarily to the reduction in continuous grain-boundary δ-phase precipitation and residual strain, together with a finer and more homogeneous grain structure, which collectively suppress local strain concentration and intergranular crack advance.