In order to explore the effect of the addition of rare earth (RE) to a steel microstructure and the consequent performance of a nitrided layer, plasma nitriding was carried out on 38CrMoAl steel in an atmosphere of NH₃ at 550 °C for 4, 8, and 12 h. The modified layers were characterized using an optical microscope (OM), a microhardness tester, X-ray diffraction (XRD), a scanning electron microscope (SEM), a transmission electron microscope (TEM), and an electrochemical workstation. After 12 h of nitriding without RE, the modified layer thickness was 355.90 μm, the weight gain was 3.75 mg/cm², and the surface hardness was 882.5 HV_0.05. After 12 h of RE nitriding, the thickness of the modified layer was 390.8 μm, the weight gain was 3.87 mg/cm², and the surface hardness was 1027 HV_0.05. Compared with nitriding without RE, the ε-Fe_2-3N diffraction peak was enhanced in the RE nitriding layer. After 12 h of RE nitriding, La, LaFeO₃, and a trace amount of Fe₂O₃ appeared. The corrosion rate of the modified layer was at its lowest (15.089 × 10⁻² mm/a), as was the current density (1.282 × 10⁻⁵ A/cm²); therefore, the corrosion resistance improved.

中文翻译：

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38CrMoAl钢表面550℃稀土等离子氮化加速

为了探索稀土 (RE) 添加对钢显微组织的影响以及渗氮层的后续性能，在 NH ₃气氛中，在 550 °C下对 38CrMoAl 钢进行等离子渗氮处理4, 8和 12 小时。使用光学显微镜 (OM)、显微硬度计、X 射线衍射 (XRD)、扫描电子显微镜 (SEM)、透射电子显微镜 (TEM) 和电化学工作站对改性层进行了表征。无稀土渗氮12 h后，改性层厚度为355.90 μm，增重为3.75 mg/cm ²，表面硬度为882.5 HV _0.05。RE氮化12 h后，改性层厚度为390.8 μm，增重为3.87 mg/cm ²，表面硬度为1027 HV _0.05。与无稀土氮化相比，稀土氮化层的ε-Fe _2-3 N衍射峰增强。RE氮化12小时后，出现La、LaFeO ₃和微量Fe ₂ O ₃。改性层的腐蚀速率最低（15.089 × 10 ^-2 mm/a），电流密度（1.282 × 10 ^-5 A/cm ²）也是如此；因此，耐腐蚀性提高。