Alsit Abdullah, Hamdan Hasan, Al Tahhan Aghyad B, Alkhedher Mohammad
Mechanical Engineering Department, College of Engineering, Abu Dhabi University, Abu Dhabi 59911, United Arab Emirates.
Heliyon. 2023 Jul 21;9(8):e18544. doi: 10.1016/j.heliyon.2023.e18544. eCollection 2023 Aug.
Stress Corrosion Cracking (SCC) is a failure mechanism that occurs when certain materials are subjected to both external or residual stresses and corrosion. This combined effect leads to the development of cracks in the susceptible materials. Submerged steel pipelines in the petroleum sector are built of low-alloy steels having a ferrite-cementite composition, including API 5L X70. Such materials are sensitive to SCC damage in aqueous systems. The film rupture dissolution repassivation (FRDR) process is used in this study to evaluate the cracks and pits growth in oil and gas pipelines in the Gulf area under diverse SCC environmental conditions. The SCC crack propagation and pit growth under near-neutral environmental conditions were analyzed using phase field modelling. X70 steel under NS4 the solution was used for the analysis to represent the anodic dissolution film rupture mechanism. A parametric study was done to study the impact of different electrochemistry and phase field parameters on crack growth behaviour. The study assess the susceptibility to SCC caused by an pit by employing diverse settings to evaluate the impact of corrosion parameters and the interaction among the FRDR mechanism. The corrosion rates are influenced by the interface kinetics coefficient (L), which exhibits an accelerated effect as L increases. This transition from fracture-controlled to dissolution-controlled SCC growth occurs until the system reaches the diffusion limit, beyond which further increases in L do not significantly impact corrosion rates. Moreover, higher values of the kinetic coefficient (k) advance the creation of SCC cracks at the crack front, resulting from corrosion originating from pitting at the crack mouth. This process leads to the refinement of the pit and its transformation into a crack. A comparison analysis was utilized to validate our simulation under a near-neutral NS4 solution for X70 steel by correlating the findings with other numerical methods for crack growth utilizing the same material and environmental parameters. The results show decent agreement with the comparative study.
应力腐蚀开裂（SCC）是一种失效机制，当某些材料同时受到外部应力或残余应力以及腐蚀作用时就会发生。这种综合作用会导致敏感材料中出现裂纹。石油行业中的水下钢质管道由具有铁素体 - 渗碳体成分的低合金钢制成，包括API 5L X70。这类材料在水系统中对SCC损伤敏感。本研究采用膜破裂溶解再钝化（FRDR）过程来评估海湾地区油气管道在不同SCC环境条件下裂纹和点蚀的扩展。利用相场模型分析了近中性环境条件下的SCC裂纹扩展和点蚀生长。使用NS4溶液中的X70钢进行分析，以代表阳极溶解膜破裂机制。进行了参数研究，以研究不同电化学和相场参数对裂纹扩展行为的影响。该研究通过采用不同设置来评估腐蚀参数的影响以及FRDR机制之间的相互作用，从而评估点蚀引起的SCC敏感性。腐蚀速率受界面动力学系数（L）的影响，随着L的增加呈现加速效应。这种从断裂控制到溶解控制的SCC生长转变一直持续到系统达到扩散极限，超过该极限后L的进一步增加对腐蚀速率没有显著影响。此外，较高的动力学系数（k）值会促进裂纹前沿SCC裂纹的产生，这是由裂纹口处点蚀引起的腐蚀导致的。这个过程会导致点蚀细化并转化为裂纹。通过将结果与使用相同材料和环境参数的其他裂纹扩展数值方法相关联，利用对比分析来验证我们在近中性NS4溶液中对X70钢的模拟。结果与对比研究显示出良好的一致性。
