氯离子对9Cr马氏体钢静态腐蚀和应力腐蚀行为的影响

目的研究9Cr马氏体钢在非服役条件下的腐蚀行为。方法运用传统电化学测试和微区扫描振动电极(SVET)技术研究材料的静态腐蚀行为,采用慢应变速率动态拉伸腐蚀试验与传统电化学测试技术相结合的方法研究材料的应力腐蚀行为。结果获得常温下氯离子对马氏体钢静态腐蚀行为的影响规律,以及慢拉伸过程中材料表面钝化膜生成和破裂过程。结论马氏体钢在氯化钠溶液中的腐蚀为阳极溶解型,且随着氯离子浓度的上升,局部腐蚀电流密度增大。常温下材料在含氯离子环境中发生弹性变形时,表面生成的钝化膜使材料的抗腐蚀性能升高。当材料进入塑性变形阶段后,由于金属表面缺陷的增多、颈缩区体积的收缩,以及钝化膜与基体金属塑性变形能力的差异,钝化膜逐渐溶解并发生破裂。

Effects of Chloride Ions on Static and Stress Corrosion Behaviors of 9Cr Martensitic Steel

The paper aims to study the corrosion behaviors of 9Cr martensitic steel under non-service conditions. The static corrosion behavior of the steel was studied by the traditional electrochemical testing technique and scanning vibrating electrode technique (SVET). The slow strain rate test (SSRT) accompanied with electrochemical tests were used to research stress corrosion behavior of martensitic steel. The effect of chloride ion on the static corrosion behavior of martensitic steel at room temperature, and the formation and breakdown of passivation film on the surface of material during SSRT were obtained. The corrosion behavior of martensitic steel in chloride environment belongs to the anodic dissolution. The local corrosion current density increases with the increase of chloride content in the environment. The results of SSRT show that the corrosion resistance of material increases during the elastic stage of SSRT due to the formation of passive film on the surface of material at room temperature. When the material enters the plastic deformation stage, the passive film is broken down due to the increase of defects on the surface of metal, the occurrence of necking zone and the deformability difference between the metal and the passive film.