Tribocorrosion Behavior Of Artificial Knee Joint Of CoCrMo Alloy With PEEK And Highly Crosslinked UHMWPE

After the artificial knee joint is implanted in the human body,it will form a new bio-friction pairs,and it is in the complex human joint operating environment.In vivo,the artificial joint implant needs to bear the comprehensive effects of the load,wear and corrosion.It also puts forward higher requirements for the design and material selection of artificial knee joint,therefore,the higher requirements for the design and selection of artificial knee joint material are also put forward.CoCrMo alloy and UHMWPE have been widely used as artificial joint material.After UHMWPE has been cross-linked by the irradiation,the wear resistance of highly cross-linked UHMWPE has been improved to some extent.As a new bone biomaterial,PEEK has gradually become a hotspot in bone and material science.In this paper,three typical joint materials of CoCrMo alloy,highly cross-linked UHMWPE and PEEK are selected to form the CoCrMo/highly cross-linked UHMWPE and CoCrMo/PEEK artificial knee joint combinations.Torsion and swing tribocorrosion behaviors of two types of joint combinations were studied.The main conclusions of this paper are as follows:In the form of torsional wear movement,the two kinds of joint combinations show a low friction coefficient at a large torsional angle.Under different normal loads,the friction coefficient increases with the large or too small normal load.The friction coefficient of CoCrMo/PEEK combination is lower than that of CoCrMo/ cross-linked UHMWPE combination.Under the form of swinging motion,the friction coefficient of the two types of joint combinations increases with the increase of the swing angle.With the increase of normal load,the friction coefficient of CoCrMo/high cross-linked UHMWPE increases,and the friction coefficient of CoCrMo/PEEK decreases slightly.The CoCrMo/PEEK friction coefficient is higher than that of CoCrMo/high cross-linked UHMWPE.The wear loss of the two kinds of joint combinations is influenced by the swing and torsion angle,and increases with the increase of angular displacement,normal load and cycle times.The wear loss of the two pairs of torsion movement is less than that of the swing movement.The wear loss of PEEK is higher than that of highly cross-linked UHMWPE under the torsion condition.Under the swing condition,the wear loss of PEEK was lower than that of the highly cross-linked UHMWPE only at the swing angle of 5°.The wear loss of PEEK was higher than that of the highly cross-linked UHMWPE in other conditions.With the increase of the torsional angle,the T-? curves of the CoCrMo/PEEK have three shapes,which changes from the linear to the elliptical and parallelogram,and the contact state at the contact interface is changed from the partial slip regime coordinated by the elasticity to the mixed slip regime and full slip regime of plastic deformation.The T-? curves of CoCrMo/high cross-linked UHMWPE combination only have the elliptic and parallelogram shapes.Under different normal load conditions,the contact state of the CoCrMo/highly cross-linked UHMWPE is in the full slip regime,and the CoCrMo/PEEK is changed from the full slip regime to the mixed slip regime.The torsional wear mechanism of high crosslinking UHMWPE is mainly the abrasive wear and fatigue wear.The damage of wear surface is serious under swinging condition,and the wear mechanism is still dominated by the abrasive wear and fatigue wear.The torsion wear mechanism of PEEK is mainly the plastic deformation in the central area,and the adhesive wear and abrasive wear are the main wear mechanisms in the outer area.An obvious transfer film can be observed on the worn surface of CoCrMo.The swing wear mechanism of PEEK is mainly dominated by the abrasive wear.When CoCrMo is paired with highly cross-linked UHMWPE,the corrosion rate rapidly increases after the start of the experiment,and then gradually stabilized.Under the torsional condition,the corrosion current of CoCrMo coupled with PEEK decreases at a later stage,and the corrosion rate gradually decreases.The surface wear increases the corrosion tendency of CoCrMo/ cross-linked UHMWPE,and has little effect on the corrosion tendency of CoCrMo/PEEK.The corrosion performance of CoCrMo and PEEK is better than that of highly crosslinked UHMWPE.