Precipitation of different types of chromium nitrides may occur during processing of super duplex stainless steels, affecting the properties of the material. In this study the influence of quenched-in (size range ca. 50-100 nm) and isothermal (size range ca. 80-250 nm) types of nitrides on the corrosion behavior of a 2507 super duplex stainless steel has been investigated at room temperature and at 90 degrees C (above the critical pitting temperature) in 1 M NaCl solution. The microstructure has been characterized by scanning electron microscopy and magnetic force microscopy. The isothermal nitrides exhibit a higher Volta potential compared to the matrix, but such difference could not be observed for the quenched-in nitrides. In-situ electrochemical AFM measurements at room temperature show stable surfaces for a wide range of applied potentials despite the presence of either type of nitrides. In the transpassive region isothermal nitrides appear to be slightly more deleterious than quenched-in nitrides. At 90 degrees C isothermal nitrides largely reduce the corrosion resistance of the austenite phase, while the quenched-in nitrides reduce the corrosion resistance of the material to a much lesser extent. The size difference between isothermal and quenched-in chromium nitrides may be crucial, in particular above the critical pitting temperature.
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机译：在超级双相不锈钢的加工过程中，可能会发生不同类型的氮化铬沉淀，从而影响材料的性能。在这项研究中，已在室温下研究了淬火（尺寸范围约50-100 nm）和等温（尺寸范围约80-250 nm）氮化物对2507超级双相不锈钢腐蚀行为的影响。 1 M NaCl溶液中的最高温度和90摄氏度（高于临界点蚀温度）。通过扫描电子显微镜和磁力显微镜表征了微观结构。与基体相比，等温氮化物显示出更高的伏特电势，但是对于淬火氮化物则无法观察到这种差异。尽管存在两种类型的氮化物，但在室温下原位电化学AFM测量显示在各种施加电势下均具有稳定的表面。在穿透区中，等温氮化物似乎比淬火的氮化物更具有害性。在90摄氏度时，等温氮化物会大大降低奥氏体相的耐蚀性，而淬火的氮化物则将材料的耐蚀性降低的程度要小得多。等温和淬火铬氮化物之间的尺寸差异可能很关键，特别是高于临界点蚀温度时。
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