The properties of the “nitrogen expanded ferrite” or α_N phase have been scarcely studied to date. This phase was obtained here on a super ferritic stainless steel (SFSS) by plasma immersion ion implantation (PIII), which is a suitable technique to produce near to surface modifications on the FeCr alloys due to the control of energy delivered to the surface. The UNS S44400 SFSS, a special alloy developed for extreme corrosion environments, was nitrided by PIII at temperatures from 300 °C to 400 °C resulting in the α_N phase as the main product of nitriding on the modified layer. The surface hardness measured by nanoindentation was investigated in the modified layers, reaching up to 3.5 times (the 400 °C condition) the hardness value presented by the untreated sample. The nitrided surfaces also presented improved corrosion resistance in comparison to the untreated sample, inferred by potentiodynamic polarization tests in NaCl electrolyte. This was evidenced by increased corrosion and pitting potentials (E_corr and E_p, respectively) and decreased corrosion and passive current densities (i_corr and i_p, respectively). Moreover, through of the analysis in the polarization curves of the nitrided samples, a greater stability of the passive layer and repassivation processes were identified. The best corrosion resistance was obtained for the sample nitrided at 300 °C, which presented the greatest reduction in i_corr and i_p (6.6 μA/cm² and 43 μA/cm², respectively) and increase in E_corr and E_p (108 mV and 214 mV, respectively), when compared to the untreated sample. In both untreated and nitrided samples, the addition of Nb and Ti in this alloy to prevent intergranular corrosion led to the formation of N- Ti-Nb-Mo precipitates that acted as initiators of pitting corrosion.

的“氮膨胀的铁素体”的或α属性_Ñ相位已几乎没有迄今研究。此相是通过等离子浸入离子注入（PIII）在超级铁素体不锈钢（SFSS）上获得的，由于控制传递到表面的能量，这是一种在Fe Cr合金上产生近乎表面改性的合适技术。在UNS S44400 SFSS，对于极端腐蚀环境开发了一种特殊合金，通过在PIII从300℃至400℃，得到的α温度氮化_Ñ相作为在改性层上氮化的主要产物。在改性层中研究了通过纳米压痕测得的表面硬度，该硬度达到未处理样品呈现的硬度值的3.5倍（在400°C条件下）。与未处理的样品相比，氮化的表面还具有更好的耐腐蚀性，这是通过在NaCl电解液中进行的电位动力学极化试验得出的。腐蚀和点蚀电位（分别为E _corr和E _p）增加以及腐蚀和无源电流密度（i _corr和i _p）降低证明了这一点。， 分别）。此外，通过对氮化样品的极化曲线的分析，确定了钝化层和再钝化过程的更大稳定性。对于300°C氮化的样品，获得了最佳的耐腐蚀性，这表明i _corr和i _p降低幅度最大（分别为6.6μA/ cm ²和43μA/ cm ²），E _corr和E _p升高（与未处理的样品相比）（分别为108 mV和214 mV）。在未处理和氮化样品中，为了防止晶间腐蚀而在该合金中添加Nb和Ti导致形成N- Ti-Nb-Mo沉淀物，该沉淀物起点蚀的作用。