Ball-disk Fretting Corrosion Test Study Of Typical Head-neck Materials Of Artificial Hip Joint

With the development of modern medicine,artificial hip arthroplasty has become the main method to treat joint failure.The modular hip joint design provides doctors with the flexibility to adjust eccentricity,combination and other parameters.However,the complex physiological environment and the periodic physiological load make the head-neck interface prone to fretting corrosion,which leads to problems such as osteolysis and adverse tissue reactions.Therefore,studying the fretting corrosion mechanism of the head-neck interface of artificial joints has important clinical significance.In this study,four typical head-neck combination interface materials of Ti6Al4V,316L,CoCrMo,and Al₂O₃ ceramics were used as research objects,and 10%bovine serum physiological saline was used as the research medium.The galvanic corrosion behavior of different metal combinations,the fretting corrosion behavior of three metal materials at the head-neck positions,and the fretting corrosion behavior of typical head-neck material combinations were studied.Combining different analysis methods,the fretting corrosion damage mechanism of the hip joint interface was revealed.The following conclusions were reached:1.In the galvanic corrosion test,Ti6Al4V alloy served as the anode,and 316L stainless steel and CoCrMo alloy served as the cathode.With the increase of coupling time,the galvanic current between 316L stainless steel and Ti6Al4V alloy,CoCrMo alloy and Ti6Al4V alloy decreased.The galvanic current between 316L stainless steel and Ti6Al4V alloy was lower than the galvanic current between CoCrMo alloy and Ti6Al4V alloy.316L stainless steel and CoCrMo alloy were subjected to cathodic protection,the resistance value increased after the end of the coupling,and the corrosion kinetics weakened,while the Ti6Al4V alloy acted as the anode,the resistance value decreased and the corrosion kinetics increased after the coupling end.2.In the fretting corrosion test of three head-neck metal materials,316L stainless steel was located in the slip zone at the anode potential of 0.5V and 0V,and the mixed zone and slip zone coexisted at the cathode potential of-0.6V.CoCrMo alloy was located in the mixed region and the slip region at the anode potential of 0.5V and 0V,respectively,while the mixed region and the slip region coexisted at the cathode potential of-0.6V.The Ti6Al4V alloy was in the slip region at the anode potential of0.5V and the cathode potential of-0.6V,while at 0V,the mixed region and the slip region coexisted.At the same anode potential of three metal materials,the friction coefficient of 316L was the largest,and the friction coefficient of CoCrMo alloy was the lowest.At the same cathode potential,the friction coefficient of Ti6Al4V alloy was the largest,and CoCrMo alloy was still the smallest.The polarization curve and impedance spectrum results show that the three metal materials exhibited different corrosion characteristics under anodic polarization and cathodic polarization.At the anode potential,the repassivation speed of 316L stainless steel was the slowest after the fretting was completed.The film integrity was the worst,and the corrosion tendency was large.The repassivation speed of Ti6Al4V alloy was the fastest,the passivation film was the most complete,and the corrosion tendency was small.At the cathode potential,the integrity of the passive film of Ti6Al4V alloy was the worst,and the tendency of corrosion was large.The integrity of the passive film of 316L stainless steel was the best,the thickness of the passive film was the thickest,and the corrosion tendency was small.3.In the fretting corrosion test of three typical head-neck material pairings,Al₂O₃ceramic paired with Ti6Al4V alloy and 316L paired with Ti6Al4V alloy,as the load increased,the fretting area gradually changed from the slip zone to the mixing zone,but the CoCrMo alloy paired with Ti6Al4V alloy was always in the slip zone.Among the three types of pairings,the friction coefficient of CoCrMo alloy and Ti6Al4V alloy pair was the lowest under the same load,and the friction coefficient of Al₂O₃ ceramic and Ti6Al4V alloy pair was the highest under the same load.With the combination of316L stainless steel and Ti6Al4V alloy,the corrosion current density was the smallest,the resistance value was the largest,the substrate had the strongest repassivation ability after the fretting,and the substrate had the lowest tendency to corrode.The Al₂O₃ceramics and Ti6Al4V alloy had the highest corrosion current density,the smallest resistance value,the weakest repassivation ability,and the largest substrate corrosion tendency.Based on the above experimental research,the galvanic corrosion tendency of the combination of 316L stainless steel and Ti6Al4V alloy was the lowest,and due to the good corrosion resistance of 316L at the cathode potential,it can be speculated that the combination of 316L stainless steel and Ti6Al4V alloy had good repassivation performance due to 316L stainless steel material transferred to the matrix material,so that it corrosion tendency was low,indicating that the selection of the head and neck pair under the 316L and Ti6Al4V alloy can reduce the risk of fretting corrosion.The key to affecting the fretting corrosion of artificial joints lies in the competitive mechanism of the formation and destruction of passive films.Therefore,when designing artificial hip joints,attention should be paid to the rational selection of materials and material pairs to reduce galvanic corrosion and fretting corrosion risk.