相变组织对奥氏体合金焊件环境氢脆的作用机制研究

The premature failure of austenitic alloy weldment in high-pressure hydrogen environment is caused mainly by hydrogen environment embrittlement(HEE), which seriously endangers the safety and reliability of the high-pressure hydrogen system. Our previous study shows that it can retard hydrogen embrittlement by a reasonable control on the microstructure after phase transformation(MPH) change induced by the couple effect of high-pressure hydrogen, weldment residual effects and structural load. However the effect of MPH on HEE is still unclear. In this project the effect of MPH on hydrogen accumulation, hydrogen induced crack and mechanical property of austenitic alloy weldment in high-pressure hydrogen environment will be studied based on our previous research. A coupled hydrogen diffusion- structure stress simulation model will be established, and the mechanism of the effect of MPH on hydrogen accumulation will be explored. The nucleation and coalescence feature of hydrogen induced crack will be analysed, in order to reveal the influence of MPH on hydrogen induced crack. Then a correlation of welding process, MPH, hydrogen accumulation and hydrogen damage will be investigated. The evolution mechanism of hydrogen damage of austenitic alloy weldment in high-pressure hydrogen environment is also studied. Finally, a control method of adjusting MPH change can be proposed via welding procedure optimization, in order to avoid HEE. The research results can provide new ideas and theoretical basis for the performance prediction and control of the weldments used in high-pressure hydrogen system.

环境氢脆是导致高压氢环境中奥氏体合金焊件过早失效的主要原因，严重危及高压氢系统的安全可靠性。前期研究发现，合理控制高压环境氢、焊接残余影响与结构载荷耦合驱动下的相变组织的形成可提高奥氏体合金焊件的抗氢脆能力。针对相变组织对环境氢脆的作用机制尚不明确的现状，本项目在前期研究的基础上通过研究高压氢环境中奥氏体合金焊件的氢富集特征、氢致裂纹行为以及氢脆性能，结合氢浓度场—结构应力场耦合的数值模型，探究相变组织对氢富集的作用机制，探讨氢致微裂纹的形成特征、聚合机制。研究从氢致微裂纹萌生、聚合到宏观主裂纹扩展的演化规律；揭示相变组织对氢致裂纹行为的影响机理。构建焊接工艺-相变组织-氢富集-氢致损伤的关联机制，解明相变组织对高压氢环境中奥氏体合金焊件氢致损伤演化的作用机理。进而通过焊接工艺的优化实现相变组织的合理调控从而有效预防氢致损伤，为高压氢系统焊接承载件性能预测与调控提供新思路和理论依据。

氢脆是导致高压氢系统奥氏体合金焊件过早失效的主要原因，严重危及高压氢系统的安全可靠性。本项目以奥氏体合金焊件为研究对象，开展相变组织对奥氏体合金焊件氢富集特性和氢脆性能影响的研究，探讨相变组织对奥氏体合金焊件氢致损伤的作用机制。通过研究，得到以下主要结论：①阐明了焊接热输入对相变组织的数量、大小及形态的影响，探明了奥氏体合金焊件相变组织的演化特性，发现氢富集在铁素体-奥氏体相界处。②解明了焊接工艺-相变组织-氢富集-氢致损伤四者关联机制。焊接影响相变组织（铁素体、马氏体、晶格取向、孪晶等）的形成，进而促进氢在相界处的偏聚和富集，氢富集区域诱发氢致微裂纹萌生，继而演化为焊件的氢致损伤。③获得了抗氢脆性能高于母材的奥氏体合金焊件，提出了基于热输入调控相变组织进而提升奥氏体合金焊件抗氢脆性能的焊接工艺优化方法，建立了基于石墨烯阻氢涂层的奥氏体合金焊件抗氢脆技术。本项目的研究成果为奥氏体合金焊件氢致损伤的防控提供了理论依据和技术支撑，有力保障加氢站用高压氢系统焊接承载件的安全可靠运行。