2012 年 63 巻 2 号 p. 113-
Bright nitriding of SKD61 tool steel was conducted in electron-beam-excited plasma using neutral nitrogen species. In this study, particular attention was devoted to the effects of nitrogen species on the surface properties of treated samples. Interaction of the neutral species and the surface was obtained by repelling the positive ions. Thereby, the sample is controlled to have greater positive plasma potential. This paper describes nitriding with neutral nitrogen species and nitrogen ion, respectively designated as neutral and ion nitriding. The hardness, surface properties, and brilliance of the neutral nitrided samples were compared with those of samples treated by ion nitriding. The surface hardness of neutral and ion nitrided samples were more than twice those of the untreated samples. However, the ion-nitrided sample had markedly higher surface roughness with a thick compound layer. The surface of the neutral nitrided sample had a mirror finish resembling that of the untreated sample. These results show that neutral nitriding can be important for nitriding high-precision mechanical parts.