片状氮化铁材料制备与分析

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Abstract：Itis focused on the study of traditional gasnitriding treatment forpure iron （400μm） ）.Threedifferent nitriding methods have been applied which include nitriding by constant temperature cycle，nitriding by highlow temperature cycle and nitriding by intermediate annealing cycle.These methods were employed to reveal the evolution ofFe-N phase microstructure and the grain boundary diffusion mechanism.By compared with the changes of compound layer in composition， microstructure and thickness，the gas nitriding process was further optimized. As the nitriding progresses，acicular γ′ phase precipitates preferentially in the surface compound layer and the vicinity of the grain boundary，exhibiting a clear preferred orientation. Annealing after nitriding helps nitrogen atoms to permeate more uniformly into the substrate，reducing the precipitation of acicular γ′ phase and facilitating theformation ofεphase which is thicker and more stable.Theε phase acts asa difusion path，forming a diffusion networkwiththe grain boundaries.

Keywords：gasnitriding;grain boundary;annealing;thecompound layer

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在纯铁气体渗氮过程中，N原子优先沿纯铁的表面扩散，当N含量超过基体α-Fe中的溶解度极限时，首先形成N浓度较低的 γ′-Fe4N 相，随着渗氮时间的增加， γ 相开始形成连续的薄层；当γ'相外侧N浓度达到饱和浓度时，即产生 .c.Fe2-3N 相[1，2]；若渗氮时间再延长，γ相薄层逐渐向内推移，ε相逐渐长大相互连成一片并继续向内生长。（剩余5316字）