LaFeO3钙钛矿氧化物加速AISI 4140钢的低温气体氮化,Applied Surface Science

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LaFeO3钙钛矿氧化物加速AISI 4140钢的低温气体氮化
Applied Surface Science ( IF 6.3 ) Pub Date : 2019-02-01 , DOI: 10.1016/j.apsusc.2018.10.111
Xing Chen , Xiangyun Bao , Yang Xiao , Chengsong Zhang , Lina Tang , Lei Yao , Guodong Cui , Yang Yang

摘要稀土渗氮被认为是提高渗氮效率的有效方法。然而，由于氮化过程中稀土（RE）元素存在的不确定性，催化机制尚不清楚。在目前的工作中，首次尝试将 LaFeO3 钙钛矿氧化物用作气体氮化的催化剂。研究了渗氮温度对稀土渗氮层组织和性能的影响，探讨了稀土的催化机理。分别采用光学显微镜、X射线衍射仪和显微硬度计对渗氮层的显微组织、相组成和显微硬度分布进行了表征。通过动电位极化技术测试氮化层的耐腐蚀性。应用销盘式摩擦计来评估磨损性能。X射线光电子能谱和配备能量色散X射线光谱的扫描电子显微镜通过分析氮化表面的化学状态和元素分布来确定稀土的催化机理。结果表明，气体氮化后会形成钙钛矿型氧化物LaFeO3，具有明显的催化活性并增加氮化层的厚度。此外，添加稀土元素渗氮后，机械性能和腐蚀性能也得到改善。LaFeO3 钙钛矿氧化物可以通过调节吸附氮 (N) 和溶解 N 的比例来加快氮化速度。另一方面，

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Low-temperature gas nitriding of AISI 4140 steel accelerated by LaFeO3 perovskite oxide

Abstract Rare earth nitriding was considered as an effective method to accelerate the nitriding efficiency. However the catalytic mechanism was not clear due to the uncertainty of rare earth (RE) elements’ existence during nitriding. In the present work, the LaFeO3 perovskite oxide was attempted to use as a catalyst in the gas nitriding for the first time. The effect of nitriding temperature on the microstructure and properties of the RE nitrided layer was investigated and the catalytic mechanism of the RE was discussed. The microstructure, phase composition and microhardness profiles of nitrided layers were characterized by the optical microscope, X-ray diffraction and micro-hardness tester, respectively. The corrosion resistance of nitrided layers was tested by the potentiodynamic polarization technique. Pin-on-disc tribometer were applied to evaluate the wear property. The X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy dispersive X-ray spectroscopy were used to identify the catalytic mechanism of the RE by analyzing the chemical state and elemental distribution on the nitrided surface. The results show that a perovskite-type oxide, LaFeO3, would form after the gas nitriding, which presents an obvious catalytic activity and increases the thickness of nitrided layers. In addition, the mechanical and corrosion properties could also be improved after nitriding with RE addition. The LaFeO3 perovskite oxide could accelerate the nitriding rate by adjusting the ratio of the adsorbed nitrogen (N) and dissolved N. On the other hand, the sufficient oxygen vacancies in the LaFeO3 oxide could provide more diffusion routes for N atoms.

更新日期：2019-02-01

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