高氮不锈钢（HNSSs）具有优异的力学性能和良好的耐腐蚀性能，作为工程结构材料具有广阔的发展和应用前景。氮合金化显著提高了不锈钢在含氯离子溶液中的耐点蚀性能，不锈钢中以氮替代镍具有重要的理论和实际意义。本文采用电化学测试、表面化学分析、腐蚀浸泡和显微分析等方法研究了含氮量、冷变形和敏化处理对无镍奥氏体HNSSs在含氯离子溶液中的抗蚀性能和再钝化性能的影响。结果表明：1)固溶氮改进了HNSSs在0.5 M H2SO4溶液中钝化膜的保护性能，提高了HNSSs在3.5% NaCl溶液中的抗点蚀性能，在0.5 M H2SO4+0.5 M NaCl溶液中，氮影响整个阳极极化区间：不仅提高了阳极溶解阻力，而且促进了吸附和钝化过程的发生，提高了钝化膜的保护性，抑制了点蚀发生。2)在3.5% NaCl溶液中冷变形降低了HNSSs的抗蚀性，随冷变形量增加点蚀电位降低。电化学阻抗谱、Mott-Schottky曲线和X射线光电子谱分析表明，HNSSs抗蚀性下降是钝化膜的保护性能弱化造成的，而冷变形引入的变形带和高密度缺陷是导致钝化膜性质变差的原因。极化测量后样品表面点蚀坑的大小和分布不随冷变形量发生明显变化，而浸泡实验的结果却表明冷变形影响点蚀坑的大小和密度，这可能是实验方法的差别造成的。3)在0.5 M H2SO4+0.5 M NaCl溶液中，冷变形对HNSSs抗蚀性的影响并不明显，可能与强酸性溶液中钝化膜的保护性变弱和钝化膜中合金元素扩散过程有关。敏化处理后的HNSSs在3.5% NaCl和0.5 M H2SO4+0.5 M NaCl 溶液中的抗蚀性随冷变形量增加明显下降，原因是冷变形加速了敏化过程中抗蚀性元素在基体中的贫化。0.5 M NaOH+0.5 M NaCl碱性溶液中，尽管钝化膜的保护性也发生变化，但冷变形和敏化处理对HNSSs的抗蚀性能几乎没有影响。4)循环极化测量结果表明，增加含氮量明显提高了HNSSs的再钝化能力，而敏化处理对其再钝化能力有所削弱，冷变形虽然降低了HNSSs的点蚀电位，但提高了其再钝化能力，HNSSs在碱性溶液中的再钝化性能较好。
其他摘要
High nitrogen stainless steels (HNSSs) have excellent mechanic and anti-corrosion properties as a new class of engineering materials, which make them attractive for various applications and extensive development. Nitrogen alloying significantly enhances the pitting corrosion resistance of stainless steels in chloride-containing solutions. The substitution of nickel by nitrogen in stainless steels has both theoretical and practical meanings. The effects of nitrogen, cold work and sensitization treatment on the corrosion resistance and repassivation ability of nickel-free HNSSs in chloride-containing solutions have been investigated by electrochemical tests, surface chemical analysis, immersion tests and microscopic observations. The following results were obtained: 1) the passive film stability was enhanced in 0.5 M H2SO4 and the pitting resistance was improved in 3.5% NaCl solution by more nitrogen solution in the HNSSs. The influence of nitrogen extended the whole anodic polarization region in 0.5 M H2SO4 + 0.5 M NaCl solution, as demonstrated by the enhanced dissolution resistance, promoted adsorption and passivation process, improved film protection and pitting resistance with increasing nitrogen content. 2) Potentiodynamic polarization revealed that pitting resistance of the HNSSs was degraded by cold work as convinced by the decreased critical pitting potential. This could be due to a less compact and protective anodic passive film based on the results of electrochemical impedance spectroscopy, Mott-Schottky measurement, X-ray photoelectron spectroscopy analysis. The growth of such an imperfect passive film could be attributed to a high density of deformation bands and other defects introduced by cold work. The pitted specimens after polarization tests showed no obvious change in size and density of corrosion pits with increasing cold work level, whereas immersion tests showed varied pit density with cold work level. This discrepancy may be resulted from the different test methods. 3) No obvious degradation on corrosion resistance took place in 0.5 M H2SO4+0.5 M NaCl solution, possibly related to the lower stability of passive film in acidic solutions as well as the diffusion process of alloying elements in passive films. Sensitized HNSSs showed degraded corrosion resistance with increasing cold work level in both 3.5% NaCl and 0.5 M H2SO4+0.5 M NaCl solutions due to the reduction of anti-corrosion elements in the matrix during cold work accelerated precipitation process. The cold work and sensitization treatment showed no influence on corrosion resistance of the HNSSs in 0.5 M NaOH+0.5 M NaCl solution even though the property of passive films was changed. 4) The cyclic polarization results in chloride solutions with different pH level showed the increasing nitrogen content improved the repassivation ability of the HNSSs, which, however, was degraded after sensitization treatment. Cold work though decreased its pitting potential, enhanced the repassivation ability. The HNSSs exhibited better repassivation ability in alkaline solutions.
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