Microstructure Regulation And Performance Characterization Of Carbon Films On Micro-arc Oxide Coated Titanium

As hard tissue implant materials,medical titanium and its alloys have attracted more and more attention in the field of medical devices due to their biocompatibility,corrosion resistance and excellent comprehensive properties.In order to synchronously improve the protective and biological properties of titanium implants,a MAO/DLC coating consisting of micro-arc oxidation(MAO)inner layer and diamond-like carbon(DLC)outer layer was designed on the titanium substrates.Microstructure regulation,bonding strength evaluation and performance characterization of the coatings were studied,which provided experimental support for further improving the preparation process of bio-active coatings on the titanium substrates.The results are as follows:(1)DLC-1,DLC-2 and DLC-3 films were deposited on the MAO coted pure titanium substrates using linear ion beam deposition,magnetron sputtering and plasma enhanced chemical vapor deposition,respectively.All the three coatings have a sealing effect.Especially,the MAO/DLC-3 coating has the most remarkable sealing effect.The MAO/DLC-1 coating has the highest adhesion(33.29N),the hardness value reaches 16.7GPa,the wear rate in SBF solution is 6.76×10-15m3/Nm and the corrosion current density is 3.37×10-10A/cm2,which is an order of magnitude lower than the MAO/DLC-2 and MAO/DLC-3 coatings.(2)The adhesion of MAO/DLC coating prepared by linear ion beam deposition is better than the traditional Ti/DLC coating.The MAO/DLC coating exhibits low friction coefficient(0.07)and low wear rate(7.01×10-15m3/Nm)in SBF solution,and the wear rate is an order of magnitude lower than MAO coating,which is three orders of magnitude lower than the uncoated Ti substrate.Meanwhile,the corrosion resistance of MAO/DLC coating is also improved.It has excellent cell adhesion and biological activity,but a poor bactericidal property.(3)In order to further improve the bactericidal property of the MAO/DLC coating,MAO/Ag-DLC,MAO/N-DLC and MAO/(Ag:N)-DLC coatings were prepared by doping the Ag and N elements into the DLC films.The results shows that both MAO/Ag-DLC and MAO/(Ag:N)-DLC coatings exhibits excellent bactericidal property,and the bactericidal rate is close to 100%after 12 hours.The wear rate of the MAO/(Ag:N)-DLC coating is an order of magnitude lower than other coatings due to Ag element existing in the DLC film in the form of Ag and Ag2O,which plays an effective role in friction reduction and lubrication.Compared with the MAO/Ag-DLC and MAO/N-DLC coatings,the corrosion resistance of the MAO/(Ag:N)-DLC coating is also improved.