Fatigue life tests and fatigue crack growth rate (FCGR) tests in the air and water environment were conducted on X80 pipeline steel welded joints (welded by CO₂ arc welding). Scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) were utilized to investigate the internal influential mechanisms of the water environment during fatigue crack initiation and propagation stages, respectively. Results show that a great many oxide particles induced by the water environment gradually formed the fatigue crack initiation site and decreased fatigue life of welded joints. Meanwhile, the preferred grain orientation of <001>//ND and CSL boundaries of Σ3, Σ11, Σ13c, Σ17b, Σ25a, and Σ25b are both prone to fatigue propagation when loading in the water environment. In addition, a coalescence of the stress intensity factor (SIF) range and water environment accelerated FCGR by motivating secondary slip systems of {112}<111> and {123}<111> in bcc crystalline structures.

中文翻译：

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水环境对X80高强度钢CO2弧焊接头疲劳性能的影响

在X80管线钢焊接接头（CO ₂焊接）上进行了空气和水环境下的疲劳寿命测试和疲劳裂纹扩展率（FCGR）测试。电弧焊）。利用扫描电子显微镜（SEM）和电子背散射衍射（EBSD）分别研究了疲劳裂纹萌生和扩展过程中水环境的内部影响机理。结果表明，水环境引起的大量氧化物颗粒逐渐形成了疲劳裂纹萌生点，降低了焊接接头的疲劳寿命。同时，当在水环境中加载时，<001> // ND的优选晶粒取向和Σ3，Σ11，Σ13c，Σ17b，Σ25a和Σ25b的CSL边界都易于疲劳传播。另外，应力强度因子（SIF）范围与水环境的合并通过激发bcc晶体结构中的{112} <111>和{123} <111>的次生滑动体系而促进了FCGR。