The Properties Of The Industrial Pure Iron Modified By Nitrogen High Frequence And Low Voltage Plasma Immersion Ion Implantation (HLPⅢ) And Nitriding

Uranium is a kind of important nuclear material, whose corrosion resistance is weak, and thus the protection of uranium against corrosion is an important subject in nuclear technology, especially for long term storage of non-irradiated components. Plasma immersion ion implantation is a well-known method for protection of metals against wear, fatigue and corrosion. So high frequency and low voltage plasma immersion ion implantation (HLPIII) nitriding technology at different RF power and O2 partial pressure has been applied to improve the industrial pure iron (simulation material of uranium) properties in this paper. Then the nitriding layer prepared by high frequency and low voltage plasma immersion ion implantation (HLPIII) nitriding technology with different pulse frequency on the ball was synthesized.After the HLPIII treatment, mechanical property and corrosion resistance of samples were evaluated and compared with the virgin Fe. The microstructure of the nitriding layer was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy(XPS). The thickness of nitriding layer was evaluated by scanning electron microscopy (SEM). The microhardness was analyzed by HXD1000 microhardness meter, the wear resistance was analyzed by CSEM pin-on-disk wear testing machine, and the corrosion resistance was measured in a 0.9% NaCl solution at room temperature. The porosity ratio was calculated using coulometric method based on the polarization curves.The result indicated that the nitriding layer was synthesized on industrial pure iron using high frequency and low voltage plasma immersion ion implantation (HLPIII) and nitriding technology. The RF power influenced the phase structure and the depth of the nitriding layer of industry pure iron. With the RF power increased, the depth of the nitriding layers was increased to 3μm from 1μm, the hardness, wear resistance and corrosion resistance were raised. The O2 partial pressure influenced the formation of iron nitride. When the O2 partial pressure was less than 6.5×10-3Pa, the existence of residual oxygen didn't influence the structure and properties of the nitriding layer. And the Fe2N and Fe3N coexisted in the nitriding layer, the nitriding layer had higher hardness, wear resistance and corrosion resistance. However, with the O2 partial pressure increased (>9.4×10-3Pa), the phase structure Fe3N and Fe3O4 was formed in nitriding layer, and the hardness, wear resistance and corrosion resistance decreased with the increasing of O2 partial pressure. The hardness, wear resistance and corrosion resistance of the ball were significantly increased after the treatment of HLPIII, and had better uniformity. Pulse frequency had no significant imfluence on hardness, wear resistance and corrosion resistance of the ball treated by HLPIII.