抄録
High-density RF induction plasma having a density of 1013cm-3 was generated using 13.56MHz 350W RF power Anticipating the effect of high-density ions, we applied the high-density nitrogen plasma to surface nitriding of iron A nitrided layer consisting of Fe3N and Fe4N was obtained at 550°C without applying a bias voltage When -200V of bias voltage was applied to the iron substrate, the main product at the surface was Fe3N having a higher nitrogen content than Fe3N obtained without bias voltage This bias voltage enabled us to nitride the iron surface even at 350°C The Vickers hardness of the surface obtained by conventional low-density plasma at 550°C was 360Hv Using high-density plasma, we obtained 980Hv Vickers hardness increased to 1390Hv when we applied a bias voltage of -100V The maximum hardness, 1410Hv, was obtained at 550°C by applying -200V The Vickers hardness of the surface prepared at 350°C with -200V bias voltage was 970Hv, comparable to that prepared at 550°C with no bias voltage The thickness of the nitriding layer obtained at 550°C with a bias voltage of -200V was 1.9μm, thinner than that obtained by conventional plasma under the same nitriding conditions We concluded that a large amount of nitrogen ion species in the high-density plasma significantly affects iron nitriding, especially surface hardness
