目的 研究电磁感应加热、等离子轰击以及电阻热效应在氮化过程中对氮化层组织性能的影响规律。方法 通过电磁感应真空脉冲氮化、等离子氮化以及真空氮化技术，对38CrMoAl钢进行氮化处理，并利用光学显微镜、SEM、X射线衍射仪、电子背散射衍射、自动显微硬度仪等仪器，对氮化层的微观形貌、相成分、晶体形态、硬度梯度等进行测试分析。结果 38CrMoAl钢经三种方式分别氮化后，氮化层主要为Fe2N、Fe3N相结构，晶粒以0.5~2.5 μm的小尺寸晶粒为主，取向差以小于5°的取向差为主。电磁感应加热容易导致氮化层中白亮层较厚，ε相含氮量高，表面硬度达到1200HV0.5，但过渡层的界面不平整。等离子轰击下的氮离子扩散能力相对较强，致使38CrMoAl钢氮化层厚度高达240 μm，0.5~2.5 μm的小晶粒和小于5°的取向差分布分别为81%、73%。电阻加热的真空氮化，氮化层厚度仅为90 μm，氮化层小尺寸晶粒和小角度取向差的分布分别为76.4%和71.9%。结论 在氮化过程中，电磁感应加热集肤效应有助于氮化层获得高氮含量和较高表面硬度。等离子轰击能加强氮原子扩散和细化晶粒组织，获得优良的组织及性能。而电阻加热方式不能提供能量集中的反应环境，氮化效率和氮化层性能均弱于前两者。

The work aims to study the influence rules of the heating mechanism of electromagnetic induction, plasma bom-bardment and resistance heat on the microstructure of nitriding layer in nitriding process. 38CrMoAl steel was treated by elec-tromagnetic induction vacuum pulse, plasma and vacuum nitriding technology. OM, SEM, XRD, EBSD and automatic micro-hardness tester were carried out to detect and analyze the microstructures, phase composition, crystal phase and hardness gradient of these nitriding layers. After 38CrMoAl steel were nitrided by three methods respectively, the nitriding layers were mainly Fe2N and Fe3N phase structure, and small-sized crystal grains of 0.5~2.5 μm and misorientation of less than 5° were distributed. The electromagnetic induction heating facilitated the nitriding layer to obtain a higher content of ε phase and a thicker white bright layer, resulting in a surface hardness of 1200HV0.5 and uneven transition layer. Under the plasma bombardment, the nitrogen ion diffusion ability was relatively strong, resulting in the thickness of the nitriding layer of 38CrMoAl steel up to 240 μm and the distribution of small grain size of 0.5~2.5 μm and the misorientation of less than 5° were 81% and 73% respectively. However, after the vacuum nitridation of 38CrMoAl steel by resistance heating, the thickness of the nitriding layer was only 90 μm, and the distribution of the small-sized grain and the small angle misorientation in the nitriding layer were 76.4% and 71.9%. The skin effect of electromagnetic induction heating helps the nitriding layer to obtain high nitrogen content and high surface hardness. Plasma bombardment enhances the diffusion of nitrogen atoms and refines the microstructure of the grains, and obtains excellent microstructure and performance. The resistance heating method cannot provide a concentrated reaction environment, so the nitriding efficiency and the nitride layer performance are weaker than the former two.