中文摘要：

利用双层辉光等离子渗金属技术，在20号钢表面进行钨．钼一钇和钨．钼共渗，并获得合金渗层。利用扫描电镜（SEM）和能谱仪（EDS）进行微观组织分析和成分分布检测，用x射线衍射仪（XRD）进行结构分析，用Fick第二扩散定律分别计算上述二元共渗和三元共渗渗层的钨、钼扩散系数以及扩散激活能。研究表明：钨-钼-钇和钨-钼共渗渗层组织均为柱状晶，渗层与基体之间有一条分界线。稀土钇的加入细化了渗层的组织；钨．钼．钇共渗层物相主要为：Fe（W，Mo，Y），Fe3Mo，Fe17Y2，W，Y等；钨一钼共渗渗层物相主要为：Fe（w，Mo）；钇的加入使渗层中钼在距表面12～15，24～25，35～36μm处的扩散系数分别提高了1．72，1．85，2．10倍，平均增大1．89倍。而钨原子的扩散系数在加入稀土元素后减小了0．92，0．99，0．76，平均降低了0．89倍；稀土钇的加入降低了钼原子的扩散激活能，说明了稀土钇对钼具有催渗作用，但对钨没有催渗作用。

英文摘要：

W-Mo-Y and W-Mo co-diffusion alloying were carried out on the 20 steel surfaces by double glow plasma surface alloying process. The microstructure, component distribution and phase structure were investigated using scanning electron microscope, energy disperse spectroscopy（EDS） and X-ray diffraction（XRD） ; the diffusion coefficient and activation energy of diffusion of W, Mo were cal- culated using Fick＇s second law in W-Mo co-diffusion layer and W-Mo-Y co-diffusion layer. The result showed that the microstructure of co-diffusion layer was columnar crystal. There was a reaction-diffusion line between the diffusion layer and the substrate. Yttrium added in the layer could benefit to structure refining; W-Mo-Y co-diffusion layer was mainly composed of Fe （W, Mo, Y）, Fe3Mo, FeI7Y2, W, Y, while W-Mo co-diffusion layer was mainly composed of Fe （W, Mo） ; Y additive could increase the diffusion coefficient of Mo by 1.72, 1.82 and 2.10 times in the diffusion layer from the surface of 12 - 15, 24 -25, 35 -36 μm, that was increased by 1.89 times av- eragely. Yttrium led the diffusion coefficient of W to decrease by 0.92, 0.99 and 0.76 times in the diffusion layer from the surface of 12 - 15, 24 - 25, 35 -36 μm, that was decreased by 0.89 times averagely. Y additive could decrease the diffusion activation energy of Mo element. So yttrium could accelerate the diffusion process of Mo, but could not accelerate the diffusion process of W.