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<p>Hydrogen embrittlement (HE) remains an unavoidable challenge in pipeline safety applications, particularly regarding hydrogen-induced damage arising from microstructural heterogeneity in welded joints caused by the high heat input of fusion welding. In this work, friction stir welding (FSW) of X100 pipeline steel was conducted at rotation rates of 600, 400, and 300&#xa0;rpm with traverse speed of 100&#xa0;mm/min (600-100, 400-100, and 300-100), and the correlation between microstructural features and the HE behavior in the nugget zone (NZ) were investigated. The NZ at 600-100 had the lowest hydrogen storage capacity of 3.79&#xa0;ppm due to the lowest fraction of high angle grain boundaries (HAGBs). The hydrogen storage capacity increased with decreasing rotation rate because of the increase of fraction of HAGBs, and the highest hydrogen storage capacity of 4.51&#xa0;ppm was achieved in the NZ at 300-100. Hydrogen charging induced a reduction in tensile strength and elongation across all samples, with the elongation deteriorating severely. However, decreasing the rotation rate effectively mitigated the loss of uniform elongation (UE) and total elongation. Consequently, the sample at 300-100 exhibited excellent UE (12.1%) and the lowest total elongation loss (45.2%). The aforementioned superior HE resistance was ascribed to the fine ferrite/bainite microstructure, a high fraction of HAGBs, and strong {111}//ND texture, which effectively inhibited hydrogen-induced crack initiation and propagation.</p>

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Microstructural Evolution and Hydrogen Embrittlement Resistance in the Nugget Zone of Friction Stir Welded High Strength Pipeline Steel

  • 期刊论文

  • 发表日期：

    2026年5月3日

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  • Di Wang,
  • Changpei Shang,
  • Fan Yang,
  • Heng Wu

摘要

Hydrogen embrittlement (HE) remains an unavoidable challenge in pipeline safety applications, particularly regarding hydrogen-induced damage arising from microstructural heterogeneity in welded joints caused by the high heat input of fusion welding. In this work, friction stir welding (FSW) of X100 pipeline steel was conducted at rotation rates of 600, 400, and 300 rpm with traverse speed of 100 mm/min (600-100, 400-100, and 300-100), and the correlation between microstructural features and the HE behavior in the nugget zone (NZ) were investigated. The NZ at 600-100 had the lowest hydrogen storage capacity of 3.79 ppm due to the lowest fraction of high angle grain boundaries (HAGBs). The hydrogen storage capacity increased with decreasing rotation rate because of the increase of fraction of HAGBs, and the highest hydrogen storage capacity of 4.51 ppm was achieved in the NZ at 300-100. Hydrogen charging induced a reduction in tensile strength and elongation across all samples, with the elongation deteriorating severely. However, decreasing the rotation rate effectively mitigated the loss of uniform elongation (UE) and total elongation. Consequently, the sample at 300-100 exhibited excellent UE (12.1%) and the lowest total elongation loss (45.2%). The aforementioned superior HE resistance was ascribed to the fine ferrite/bainite microstructure, a high fraction of HAGBs, and strong {111}//ND texture, which effectively inhibited hydrogen-induced crack initiation and propagation.