超级13Cr油管表面全覆盖半导体预钝化膜制备及其对不锈钢点蚀坑生长行为影响机理研究

Super 13Cr tubing has being widely used in the harsh environment in oil and gas fields, and achieves good performance on corrosion resistance. However, stress corrosion cracking (SCC) induced by pitting corrosion still make super 13Cr tubing in dangerous during service. Therefore, further improving the SCC resistance of super 13Cr is great significance to the safe service of pipes and the development of oil and gas fields. It is also an urgent problem for the oil fields, such as Tarim oil field, that contain high-temperature and high-pressure wells and steel-pipe manufacturers. On the basis of the fact that pre-passivation can produce a thick corrosion-resistant film on surface of super 13Cr, this project plans to firstly set up a method to control the thickness, microstructure and semiconductor properties of pre-passive film, according to clarification of the evolution mechanism of the properties of passive film with the parameters of passivation process. Then the growth kinetics of pits on surface of pre-passivated super 13Cr in whole-life (contains four stages: acidification, residual acid, condensate water and formation water) is determined. Ultimately, based on the law of stress-level evolution at the bottoms of pits and the mechanical properties of 13Cr, a life-prediction model of pre-passivation super 13Cr will be established. In terms of all above results, the theoretical guidance for the preparation and safe service of 13Cr pipes with high corrosion resistance can be provided.

超级13Cr油管广泛应用于油气田苛刻环境中，并展现出良好的耐蚀效果。然而，点蚀诱发的应力腐蚀开裂问题仍然是超级13Cr油管安全服役的一大困扰。因此，进一步提升13Cr耐应力腐蚀开裂的能力对管材安全服役及油气田开发具有重要意义，也是目前塔里木等含有高温高压油气井的油田及钢管生产厂家亟需解决的问题。基于预钝化能够在超级13Cr表面制备一层耐蚀薄膜的事实，本项目在阐明预钝化膜性能随钝化工艺参数演变机理的基础上，建立可调控预钝化膜厚度、微观结构、半导体性质的方法；然后明确预钝化超级13Cr油管表面点蚀坑全生命周期（包括酸化、残酸、凝析水与地层水四个阶段）生长动力学行为；最后基于点蚀坑底部应力水平演变规律及管材力学性能建立预钝化超级13Cr油管全生命周期服役寿命预测模型，为高耐蚀性超级13Cr管材的制备及安全服役提供理论指导和依据。

超级13Cr油管广泛应用于油气田苛刻环境中，并展现出良好的耐蚀效果。然而，点蚀诱发的应力腐蚀开裂问题仍然是超级13Cr油管安全服役的一大困扰。本项目针对13Cr不锈钢点蚀造成的应力腐蚀开裂问题，开展了预钝化膜微观结构及半导体性质调控研究，预钝化膜对超级13Cr不锈钢耐蚀性能影响研究，预钝化超级13Cr在全生命周期内点蚀坑的生长动力学行为研究，以及预钝化超级13Cr全生命周期服役寿命预测模型研究。首先，研究了活化处理工艺参数对超级13Cr不锈钢表面缺陷及主要元素含量的影响，明确了活化处理工艺最优参数：浸泡时间50s、温度100℃、硫酸浓度26ml/L；建立了可调控预钝化膜厚度的预钝化方法。其次，从动力学和热力学角度，分析了不同预钝化工艺下试样的耐全面腐蚀及点蚀性能，明确20min为抵抗全面腐蚀的最佳预钝化时间，揭示了13Cr马氏体不锈钢点蚀电位随预钝化膜厚度增加呈指数增加的规律。随后，开展了不同预钝化时间下超级13Cr不锈钢在油井全生命周期工况下的点蚀行为研究，与自然钝化试样相比，预钝化试样点蚀坑生长速率明显降低。最后，通过有限元模拟开展了点蚀坑应力集中分析与点蚀坑生长动力学研究，结合实验室试验结果，明确了点蚀发生时不锈钢构件仅能承受其断裂强度30%~50%的拉伸载荷，为高耐蚀性超级13Cr管材的制备及安全服役提供理论指导和依据。