中文摘要：

研究了稀土对42CrMo钢等离子体渗氮表面相结构、渗层增厚动力学及渗层显微硬度分布的影响；基于密度泛函理论，采用第一性原理赝势平面波方法计算了化合物层ε-Fe2.3N相的电子结构。XRD结果表明，稀土添加并未改变表面相结构；显微硬度结果表明，稀土添加使试样表面硬度和层渗均有所增加；态密度计算结果表明，稀土添加降低了晶胞中Fe、N的稳定性，提高了原子间的交互作用，起到了催化和强化的双重作用。

英文摘要：

The effect of rare earth （RE） on the surface phase structure, the kinetics of layer growth and the microhardness profile in surface layer during plasma nitriding of 42CrMo steel were studied. The electron structure of ε-Fe3 N phase was calculated using the plane-wave pseudo-potential method of density functional theory. The experimental results show that the addition of RE doesn＇ t change the surface phase structure of 42CrMo steel nitrided but enhances the microhardness of the surface layer and the thickness of nitrided layer. The calculated results from first-principle indicate that the RE addition reduces the stability of atoms Fe and N in lattice, at the same time enhances the bonding strength among atoms in unit cell.