Wear Resistance Of Amorphous Carbon-based Nano-multilayer Films Deposited On Metal Surface For Artificial Joints

Metal materials are widely used in artificial joint prostheses due to their excellent mechanical properties and machinability.However,the joint interface often suffers from wear and tear in the complicated service environment of human body.The metal ions and particles produced by the wear of metal materials can induce adverse biological reactions,and eventually lead to osteolysis around the prosthesis and aseptic loosening.Surface film coating modification can improve the wear and corrosion resistance of metal joint surface,and effectively prevent the release of metal ions.However,the poor adhesion strength and long-term wear resistance of the surface film coating are still the bottlenecks restricting its clinical applications.In this thesis,the wear resistance of amorphous carbon-based nano-multilayer film deposited on the surface of artificial joint metal materials was studied.The stress distribution of the film/substrate system under different parameters was studied by finite element analysis method and the initial position of the yield of the system is predicted;Meanwhile,The effects of the physical and chemical properties of the substrate on the surface properties,atomic bonding structure,mechanical properties and wear resistance of amorphous carbon-based nano-multilayer films were studied by means of optical 3D profiler,Raman spectrometer,nanoindentation instrument,coating adhesion strength scratch instrument and multidirectional motion implant material wear machine.The results in this thesis can not only provide theoretical guidance for the optimization design of film parameterization,but also provide technical support for the optimization of surface modification and tribological improvement of artificial joint metal materials.The research work of the thesis mainly includes:（1）Research on stress distribution and yield position prediction of film/substrate system based on finite element method:In the soft film system,when the friction coefficient is small,the Mises stress on the inner of the substrate and the film,the interface is relatively large,and an increase in the friction coefficient is the main factor that causes the maximum Mises stress position to move upward.The initial yield position of the system is also basically located on the interface and the surface of the film.Compared with the soft film system,the hard film system has higher Mises stress on the film surface and interface at higher friction coefficient,and the initial yield position is more likely to occur on the film surface.（2）The effect of surface roughness of titanium alloy substrate on the comprehensive properties of amorphous carbon-based nano-multilayer films was studied.The amorphous carbon-based nano-multilayer films were deposited on four different surface roughness surfaces of titanium alloy（Sa values of 4nm,60nm,110nm and 150 nm,respectively）in the same furnace.The influence of surface roughness on the comprehensive properties of the films was studied.The results show that the surface roughness of the film is higher than that of the corresponding substrate,and the surface roughness of the film has the same variation trend with the substrate.The hardness and modulus of elasticity of the films（approximately7.1 GPa and 121.1 GPa,respectively）were not affected by the surface roughness of the substrate.The scratch test shows that the increase of the surface roughness of the smooth substrate in a small range can improve the adhesion strength of the films,but it decreases rapidly with the further increase in the roughness.The indentation results indicate that adhesion strength decreases as the substrate roughness increases.The film deposited on the extreme smooth substrate surface（Sa is about 4 nm）shows the best wear resistance,and its wear factor is only about 2.55×10^-1717 m³ N^-11 m^-1.While the wear resistance of the films on the surface of the larger roughness substrate（Sa is about 150 nm）decreases sharply,wear factor reaching 1.11×10^-1515 m³ N^-11 m^-1,and the wear of counterpart is more obvious.（3）The effects of different substrate materials on the comprehensive properties of amorphous carbon-based nano-multilayer films:The mechanical properties of the substrate have an obvious effect on the atomic bonding structure of the films.The film deposited on the surface of titanium alloy substrate forms strong chemical bonds and demonstrates excellent mechanical performance,which improving the interface state and adhesion strength of the film,and eventually exhibits relatively excellent wear resistance,the wear factor is about 2.79×10^-1717 m³ N^-11 m^-1.The atomic bonding structure and mechanical properties of the films on 316L stainless steel and Co-Cr-Mo alloy are more like to diamond.The films exhibit lower adhesion strength and wear resistance.The wear factors of the films are about 7.13×10^-1717 m³ N^-11 m^-1 and 1.25×10^-1616 m³ N^-11 m^-1,respectively.In particular,the film deposited on the Co-Cr-Mo alloy has a low adhesion strength and exhibits poor wear resistance and wear life.