Surface Modification Of Ti6Al4V Biomaterial By Hybrid Plasma Ion Implantation

Ti6Al4V alloy attracts much attention among the implant biomaterials due to its high specific strength, relatively low density and modulus, better mechanical and machining properties, favorable corrosion resistance and good biocompatibility. However, its low wear resistance and bioinertness of Ti6Al4V are major concerns in artificial applications. It is difficult for Ti6Al4V alloy to combine directly with bone tissue by chemical bonding.In this paper, acetylene, oxygen and nitrogen plasma immersion ion implantation (PIII) have been utilized to enhance the surface properties of Ti6Al4V for its unique advantage. The hardness, wear resistance, corrosion resistance and bioactivity of the samples treated by PIII have been investigated. Micro-hardness and nano-hardness of the implanted samples were measured. Wear resistance of samples was also studied systemically. The corrosion behaviour of surface has been investigated by the potentiodynamical polarization test. The specimens were incubated in simulated body fluids (SBF) at a pH of 7.42 and temperature of 37℃for 14 and 20 days respectively to evaluate the surface bioactivity. X-ray photoelectron spectroscopy (XPS) was performed to study the surface structure, such as the elemental states, etc. The morphology, structure and phase composition of the surface after incubated in SBF were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR).The results show that the micro-hardness of the Ti6Al4V surface has been significantly increased after PIII treatment. The nano-hardness at the depth of 400nm still maintains higher than that of the substrate. The results of dry ball-on-disk wear tests demonstrate that PIII can reduce friction coefficients, and there is a significant improvement of wear resistance. The improvement of wear resistance resulted from carbon, nitrogen PIII is higher than that by oxygen PIII. (C2H2+O2+N2) hybrid ion implantation also leads to the enhancement of wear resistance. However, wear resistance will be worse with increasing the RF power. In addition, too high bias voltage or long implantation time leads to negative effect. The wear resistance may be improved with increasing the gas pressure.