Surface characteristics of Ti6Al4V alloy treated by arc plasma nitriding under different nitrogen‑hydrogen ratios

The arc plasma nitriding technology has been widely applied in the field of surface engineering due to its advantages such as high production efficiency, process flexibility, and environmental friendliness. To address the issues of insufficient wear resistance and corrosion resistance of Ti6Al4V (TC4) alloy surfaces, this study employs an arc discharge-assisted ion etching (IET) device for the plasma nitriding treatment of TC4 alloy, aiming to enhance its performance. The processing conditions were set at a temperature of 500 °C, a bias voltage of 400 V, and a pressure of 1.5 Pa. Four different gas mixtures were introduced: pure nitrogen, a nitrogen‑hydrogen ratio of 2:1, a nitrogen‑hydrogen ratio of 1:1, and a nitrogen‑hydrogen ratio of 1:2. The duration of the process was maintained for 2 h. Test results indicate that the introduction of hydrogen can enhance the diffusion capability of nitrogen elements in the TC4 alloy matrix, thereby improving the nitriding effect and forming dense layers of TiN and Ti₂N. Nitriding significantly enhances the microhardness, wear resistance, and corrosion resistance of TC4 alloys. Moreover, the optimal performance is achieved when the ratio of nitrogen to hydrogen is 2:1. Therefore, the ratio of nitrogen to hydrogen in the arc plasma nitriding process significantly affects the surface properties of titanium alloys, which may contribute to enhancing the long-term service performance of TC4 alloys in the field of biomedical implants.