Surface Modification Of Titanium Alloy And Perparation Of Biomimetic Bioactive Coating

In order to improve wear resistance and corrosion resistance of Ti6Al4V alloy, reduce the side effect resulted from Al and V ion releasing, a TiN dendritic layer was prepared on Ti6Al4V alloy substrate by using laser gas nitriding (LGN) technique, and a bioactive hydroxyapatite (HA) coating was deposited on the modified substrate by chemical biomimetic method as well. The surface morphology, film composition and phase of the coating were investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The main conclusions are as follows:A TiN dendritic layer could be prepared on Ti6Al4V alloy substrate by LGN technique. Compared with the Ti6Al4V alloy substrate, under the same experimental conditions, the laser gas nitrided Ti6Al4V alloy surface layer had better wear resistance. The electrochemical corrosion test showed that the LGN specimen had a higher corrosion potential and less corrosion current compared with the substrate, furthermore, polarization resistance was four times higher than that of the substrate, which meant that corrosion resistance of LGN specimens was obviously better than that of the substrate.The bioactivity of Ti6Al4V alloy could be improved by alkali treatment combined with heat treatment, which could be attributed to formation of Ti-OH groups on the surface of Ti6Al4V Alloy. The experimental results showed that a HA coating could be formed on the modified Ti6Al4V alloy substrate after dipping in the simulated body fluid (SBF) for five days, and with the culture time increased, the deposit layer on substrate gradually thickened. The amount of Ca, P ions increased day by day, and the Ca/P ratio also changed with increase of the dipping time.The bioactivity of laser gas nitrided Ti6Al4V alloy could be modified by alkali treatment and heat treatment as well and a HA bioactive coating could be prepared successfully on the surface of the laser gas nitrided Ti6Al4V alloy. However, compared with the Ti6Al4V alloy, a longer culture time was needed. Owing to the three-dimensional dendritic TiN fabric existed on the surface of laser gas nitrided specimens, the reliable mechanical lock could be formed between the coating and the substrate, which would ensure a higher bonding strength at interface of the coating and substrate and a longer service life of the implant in human body.Ca, P ions could be introduced on the surface of Ti6Al4V alloy by pre-calcification processing, however, it seemed that there was no important role of pre-calcification processing on HA nucleation as expected, the reason still needed to be investigated further.