Study On Wear And Corrosion Behaviors Of Contact Interface Between Metallic Materials Of Artificial Hip Joint

Bio-tribology and corrosion have become key technical problems affecting the service life and reliability of artificial joint implants.Metallic materials of artificial joint mainly include CoCrMo alloy,Ti6Al4 V alloy,316 L stainless steel and other medical metals.There are wear losses of metal joint materials in human bodies,accompanied by corrosion loss and the release of metal ions.In this study,three kinds of artificial hip prosthesis materials,the friction and corrosion mechanisms of different artificial joints and the performance of ion release were studied,which provides some basic theories for artificial joints.The results are as follows:316L stainless steel has the lowest impedance value in static corrosion,indicating the thinnest inner layer of oxide film.Its Nyquist diagram transforms from linear to semi-circular and its controlling electrode process transforms from diffusion to electrochemical reaction.CoCrMo alloy's Nyquist diagram is near semi-circular,showing that the electrode process is controlled by electrochemical reaction and the diffusion is not obvious.Ti6Al4 V has the lowest impedance value in static corrosion.Its Nyquist plot is linear,representing that there isn't obvious electrochemical reaction in bovine serum and the electrode process is controlled by diffusion.The impedance values of 316 L stainless steel and CoCrMo alloy decrease greatly with time,which shows that their surface passivation films are dissolved and the film thickness is reduced.Nevertheless,the impedance values of Ti6Al4 V alloy don't decrease obviously,indicating that the dissolution of surface passive films is not obvious.Under the sliding friction test,the friction coefficient of Ti6Al4 V alloy is the highest and the wear resistance is the worst.But its corrosion tendency is the lowest,the ion concentration after wear is the lowest and the corrosion resistance is the strongest.Its wear forms are mainly abrasive and fatigue wear.The re-passivating capability of 316 L stainless steel's passivation film is the worst.Its releasing ion concentration after wear is the highest.And the corrosion resistance is the worst and the main wear forms are abrasive wear,fatigue wear and corrosion wear.Forging CoCrMo alloy has the lowest friction coefficient,the best wear resistance,the best re-passivating capability of passivation films and the best corrosion resistance.The wear mechanism of CoCrMo alloy is mainly abrasive wear.When the load is small,the electrode process of Ti6Al4 V alloy and 316 L stainless steel is basically dominated by diffusion.But the effect of charge transfer is intensified and the electrode process is still controlled by diffusion after increasing the load.The electrode reaction of CoCrMo alloy is controlled by charge transfer and diffusion.The electrochemical polarization and concentration l polarization are present at the same time.Under the torsional fretting test,the T-? curves of three metals are parallelogram,the micromovement is in the complete slip zone and there is only plastic deformation on the surface when the load is small.When the load is large,the T-? curve of CoCrMo is elliptical,the micro-motion is in the mixed slip zone and there are plastic and elastic deformations on the surface.The T-? curve of 316 L stainless steel is parallelogram,its micro-movement is in the complete slip area and there is serious plastic deformation.The T-? curve of Ti6Al4 V alloy is elliptical,the micromotion is in the mixed slip zone and there are mainly elastic deformations and less plastic deformations.Under the same load,the friction torque of CoCrMo alloy is the smallest and the friction torque of Ti6Al4 V alloy is the largest.Under the torsional fretting test,the peak value of 316 L stainless steel's phase angle is the smallest,the frequency corresponding to the peak is the maximum and its Nyquist plot is semicircular.These indicate that its passive film is the most incomplete,the corrosion damage is serious,its electrochemical reaction is the fastest,the diffusion can be ignored and the ions release of 316 L stainless steel is the largest.The peak value of forged CoCrMo alloy's phase angle is the largest and its Nyquist plot is semi-circular and linear,showing that its passive film is the most complete,the corrosion damage is slight and the electrode reaction is controlled by charge transfer and diffusion.The frequency corresponding to the peak value of Ti6Al4 V alloy's phase angle is the smallest and its Nyquist plot is almost the linear arc.These show that there aren't obvious electrochemical reactions on the surface,the electrode process is basically controlled by diffusion,the iron release rate is the lowest and its corrosion resistance is the strongest.Under the same load of the torsional fretting test,the wear of CoCrMo alloy is the lightest and the wear scar is U-shaped.There is a small amount of debris accumulated near the groove.There are furrows and fatigue peeling in the groove and none obvious corrosion is observed.The wear scar of Ti6Al4 V alloy is the deepest,the surface roughness is the highest,the wear scar is W-shaped and the wear resistance of titanium alloy is the worst.The wear scar of 316 L stainless steel is W-shaped and there are many furrows,fatigue peeling,plastic deformation and corrosion pits on the surface,indicating that the wear mechanisms are mainly abrasive wear,fatigue wear,corrosion wear and so on.