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<p>This study investigated the cracking failure of a 0Cr18Ni10Ti stainless steel nozzle flange located at the outlet pipeline of a hydrogenation reactor, which had been in service for 15&#xa0;years under a complex hydrogen-rich environment containing H<sub>2</sub>, H<sub>2</sub>S, NH<sub>3</sub>, and oil–gas mixtures at 440&#xa0;°C and 14.5&#xa0;MPa. Visual inspection, metallographic examination, electron backscatter diffraction, mechanical testing, scanning electron microscopy with energy-dispersive spectroscopy were conducted to characterize the flange. In addition, finite element analysis was carried out to evaluate the stress distribution and concentration at the groove. The crack was found to initiate at the inner edge of the trapezoidal sealing groove. Finite element analysis indicated that the maximum stress at this location was approximately 306.3&#xa0;MPa, close to the yield strength of the degraded material, confirming pronounced local stress concentration. Microstructural analysis further revealed a <i>δ</i>-ferrite content of about 14%, accompanied by intergranular carbide precipitates. These features provided pathways and trapping sites for hydrogen, thereby accelerating its ingress and promoting localized embrittlement. Fractographic analysis exhibited mixed transgranular and intergranular features, characteristic of high-temperature hydrogen embrittlement. The failure was therefore attributed primarily to hydrogen embrittlement under prolonged high-temperature and high-pressure conditions.</p>

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Failure Analysis of Cracking in the Sealing Groove of a Hydrogenation Reactor Flange

  • 期刊论文

  • 发表日期：

    2025年11月5日

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  • Shuang Hu,
  • Fenghua Su,
  • Kaisen Wang,
  • Weixiong Chen,
  • Yicheng Lu,
  • Jianfang Sun

摘要

This study investigated the cracking failure of a 0Cr18Ni10Ti stainless steel nozzle flange located at the outlet pipeline of a hydrogenation reactor, which had been in service for 15 years under a complex hydrogen-rich environment containing H2, H2S, NH3, and oil–gas mixtures at 440 °C and 14.5 MPa. Visual inspection, metallographic examination, electron backscatter diffraction, mechanical testing, scanning electron microscopy with energy-dispersive spectroscopy were conducted to characterize the flange. In addition, finite element analysis was carried out to evaluate the stress distribution and concentration at the groove. The crack was found to initiate at the inner edge of the trapezoidal sealing groove. Finite element analysis indicated that the maximum stress at this location was approximately 306.3 MPa, close to the yield strength of the degraded material, confirming pronounced local stress concentration. Microstructural analysis further revealed a δ-ferrite content of about 14%, accompanied by intergranular carbide precipitates. These features provided pathways and trapping sites for hydrogen, thereby accelerating its ingress and promoting localized embrittlement. Fractographic analysis exhibited mixed transgranular and intergranular features, characteristic of high-temperature hydrogen embrittlement. The failure was therefore attributed primarily to hydrogen embrittlement under prolonged high-temperature and high-pressure conditions.