Tc4 Titanium Alloy Surface Deposition Of Diamond Film Studies

With the advantages of low density, high strength-to-weight ratio, superior corrosion resistance, high temperature mechanical property, fatigue resistance, titanium alloy is widely used in aerospace, navigation, chemical industry, automobile and biomedicine area. But the practical use of titanium alloy and its service life is not satisfied because of its poor friction property, low wear resistance and low thermal conductivity. Diamond films have a series of excellent physical and chemical properties, such as high hardness, low friction coefficient, high wear resistance, high thermal conductivity and good biocompatibility, and so on. A well-adhesion diamond films on titanium alloy can improve its property greatly and more and more research have been taken in this field.Diamond films were deposited on Ti6A14V alloy substrates with the mixture gas of methane and hydrogen by hot filaments chemical vapor deposition (HFCVD), and a TiC interlayer was deposited on the Ti6A14V substrates using reactive magnetron sputtering. The surface and cross-section morphology of diamond films were observed by Scanning electron microscopy (SEM) and Atomic force microscope (AFM), the structure of films was investigated using X-ray diffraction (XRD) and Laser Raman spectrum, and the adhesion of diamond film was characterized by Rockwell hardness tester. The effects of process parameters such as substrate temperature, gas composition, filament-substrate distance and TiC interlayer was studied, and a method by decreasing substrate temperature gradually during the CVD diamond growth was taken to improve adhesion performance of the diamond films.Conclusion can be drawn as following:1. Diamond films can be deposited on Ti6A14V at550～750℃when the methane concentration is2～3%, air pressure2-3kPa; at lower temperature(500℃), it’s very hard to get continuation films, and high temperature(650～750℃) can cause film collapse.2. The TiC interlayer by reactive magnetron sputtering is shown to play an important role in improving the nucleation and quality and decrease the residual stress of the diamond films. But it didn’t solve the poor adhesion problem of the diamond films.3. Temperature is significant to the diamond nucleation on Ti6A14V alloy. A higher temperature can promote carbon diffusion and H atoms etching graphite, and get high quality diamond films. Simultaneously it will promote the formation of TiC interlayer. Suitable temperature is significant to the nucleation density.4. Gradient substrate temperature can increase the nucleation density and decrease the residual stress of the diamond films. A strong interface bonding between diamond and Ti6A14V can be obtained by gradient substrate temperature method at the following condition:nucleation temperature gradually reduced within30min from800℃to550℃～600℃, and grown at this temperature for7h, the methane concentration2%, air pressure3kPa.