The effect of the addition of Nb, N, and Mo to 17-4 precipitate hardening stainless steel (17-4 PH steel) on its pitting behavior in a simulated geothermal environment was investigated using a cyclic polarization test, and the pitting potentials and the repassivation potentials of the materials were acquired to evaluate their pitting resistance. Nb and N were found to lower the pitting potential of 17-4 PH steel, while Mo increased it. In the case of repassivation potential, the addition of all these elements seemed to have a slightly negative impact. Cr-rich oxide, Nb carbonitride (Nb (C, N)), and reversed austenite were found in the materials. The element distribution of/around the Cr-rich oxide inclusion and the Nb (C, N) precipitate of the material were studied. A Cr-depleted zone was found around the inclusion/precipitate, which rendered the surrounding area to be more susceptible to pitting corrosion. Pit embryos and well-developed pits were observed after the cyclic polarization tests. Pits tended to initiate in the vicinity of the inclusion/precipitate, and the dissolution of the oxide around the pit embryo was seen, which was believed to cause the local deterioration of the electrochemical environment. Lacy cover with narrow strip-shaped holes was found above the well-developed pit, and the forming mechanism of these holes was believed to be the dissolution of martensitic.

使用循环极化试验研究了在模拟地热环境中向17-4沉淀硬化不锈钢（17-4 PH钢）中添加Nb，N和Mo对其点蚀行为的影响，并研究了点蚀电位和获得材料的再钝化电位以评估其耐点蚀性。发现Nb和N降低17-4 PH钢的点蚀电位，而Mo增加。在具有重新钝化能力的情况下，所有这些元素的添加似乎都具有轻微的负面影响。在材料中发现了富铬氧化物，Nb碳氮化物（Nb（C，N））和反向奥氏体。研究了富铬氧化物夹杂物周围元素的分布以及材料的Nb（C，N）析出物。在包裹体/沉淀物中发现了一个贫铬区，这使得周围区域更容易发生点蚀。周期性极化试验后观察到了坑胚和发育良好的凹坑。凹坑倾向于在夹杂物/沉淀物附近引发，并且观察到凹坑胚周围的氧化物溶解，这被认为引起电化学环境的局部恶化。在发达的矿坑上方发现了带有窄条形孔的花边覆盖层，这些孔的形成机理被认为是马氏体的溶解。据信这会导致电化学环境的局部恶化。在发达的矿坑上方发现了带有窄条形孔的花边覆盖层，这些孔的形成机理被认为是马氏体的溶解。据信这会导致电化学环境的局部恶化。在发达的矿坑上方发现了带有窄条形孔的花边覆盖层，这些孔的形成机理被认为是马氏体的溶解。