【摘要】 研究了在脉冲等离子体稀土渗氮过程中稀土元素Ｌａ对氮浓度分布和相结构的影响，揭示了Ｌａ在化合物层中的扩散规律．结果表明：与常规离子渗氮相比，稀土元素的添加，提高了表面氮浓度，随处理时间的延长而增加；当渗氮时间从２ｈ增加至２４ｈ时，化合物层由单相ε－Ｆｅ２－３Ｎ（ε）转化为ε－Ｆｅ２－３Ｎ和γ－Ｆｅ４Ｎ（γ’）双相．此外，Ｌａ可以扩散进入ε和γ’相中．Ｌａ的扩散规律受制于化合物层中γ’－Ｆｅ４Ｎ的比例．随时间延长，化合物层中γ－Ｆｅ４Ｎ的比例增加，Ｌａ的扩散加快，且在２—２４ｈ范围内其扩散遵循指数规律。更多还原

【Abstract】 The effects of rare earth (RE) on the nitrogen concentration and phase structures of the surface of steel En40B plasma RE ion nitrided at 520℃ for 2-24 h in a 75H-25N(volume fraction,%) mixed atmosphere with the flow rate 12 L/min were measured and the diffusion law of La in compound layer was revealed. The experimental results show that the surface nitrogen concentration is increased due to the addition of RE with increasing nitriding time. When the time exceeds 4 h the thickness of the compound layer is remarkably increased by the addition of RE. The surface phases constitution is changed from mono phase ε-Fe2-3N for 2 h to dual phase ε-Fe２-3N and γ’-Fe4N for 24 h RE ion nitriding. The La can diffuse into (ε+γ’) phase range, and the surface concentration and the depth (corresponding to La concentration 0.05%) of La in compound layer increase with increasing nitriding time. The kinetics of La diffusion follows an exponential law during 2-24 h RE ion nitriding.更多还原