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纯铁的莱勒图被广泛用于选择合金钢的渗氮工艺。本文首次采用计算热力学来确定AISI 4140钢的莱勒图。研究表明，AISI 4140钢的莱勒图与纯铁的存在明显差异。对AISI 4140钢进行了渗氮试验，目的是验证计算热力学的预测结果。扫描电镜结果显示化合物层中存在两种相，利用透射电镜对化合物层与扩散层界面的研究结果证实了γ′-Fe4N和ε-Fe2－3（C，N）相的共存。这些试验结果与用计算热力学建立的AISI 4140钢莱勒图高度吻合。“,”The Lehrer diagram of pure iron is widely used to select the nitriding process of alloy steels.In the present work,the Lehrer diagram of AISI 4140 was determined for the first time by computational thermodynamics. It is demonstrated that the Lehrer diagram of AISI 4140 differs from that of pure iron significantly.Nitriding experiments for AISI 4140 were also carried out to verify the predictions from computational thermodynamics.The scanning electron microscopy results show the existence of two phases in the compound layer and the transmission electron microscopy results at the interface between the compound layer and the diffusion zone verified the coexistence of γ′-Fe4 N and ε-Fe2-3 (C,N ) phases.These experimental results agree well to the customised Lehrerdiagram of AISI 4140 constructed from computational thermodynamics.