ラジカル窒化における基板加熱法の影響

抄録

Industrial processes for plasma nitriding, such as ion nitriding and radical nitriding, are used extensively, but their daily production is severely limited by the duration of their associated heating and cooling times. Considering ecologically friendly processes and processing time reduction, near-infrared radiant（NIR）heating is a better heating method. Because NIR wavelengths are shorter than far-infrared radiation wavelengths, NIR gives higher energy input: it is better suited for heating metal. This paper presents a novel approach to reduce radical nitriding processing times. We prepared a new apparatus: an NIR heater mounted on a radical nitriding apparatus（IR-RN）.

Results demonstrated that IR-RN can reduce overall processing times from 900 to 380 min because IR-RN can increase the surface temperature immediately and cool it much faster than radical nitriding（RN）. Moreover, a sample treated using IR-RN showed the same surface hardness and roughness as the radical nitrided sample. No compound layer was observed in a surface layer with the sample treated using IR-RN.

The hardening depth of a layer treated using IR-RN for 60 min was half that of a layer treated using RN because of the temperature gradient, whereas a sample treated using IR-RN（513 K bottom temperature）for 300 min and IR-RN（573 K bottom temperature）for 180 min and 300 min were the same depth as the RN sample layer.