Tribology Desgin And Wear Resistance Research Of Magnesium Artificial Hip

The traditional materials which were used for artificial hip joint affect its performancecharacteristics in biological compatibility, wear resistance, corrosion resistance, etc.Developing newly artificial hip joint materials to improve its performance characteristics andservice life is becoming an important method in the present research. Magnesium alloys exhibita series of advantages such as rich resources, outstanding biocompatibility and biodegradabilityin physiological environment, which make them become an ideal biomedical materials forimplant applications. But poor wear resistance and fast corrosion limit their medical application.Micro-arc oxidation technology which preparing a coating on the raw material surface, canimprove the performance in wear and corrosion resistance of the raw material.In this work, magnesium alloy hip joint tribology design was carried out. The magnesiumalloy artificial hip stem was prepared by the investment casting method, and it shows that thiskind of hip joint stem can bear a maximum force of3271N. The contact pressure of thisartificial hip joint which use ultra high molecular weight polyethylene (UHMWPE) asacetabular material in static and gait loads were also analyzed by ABAQUS software. In staticload, magnesium alloy artificial femoral head bearing the maximum contact stress was9.125MPa, but UHMWPE artificial acetabulum got high strain values; during the gait loads,UHMWPE artificial acetabulum was always under the maximum contact stress. It can bededuced that an alternation between the joint pairs to bear maximum stress between dynamicand static load, maybe this is helpful to improve the service life of the joint, but the advantageis not significantly.In order to improve the tribological properties and corrosion resistance of the magnesiumalloy artificial hip joints, micro-arc oxidation technology was used for preparing surfacecoating. The effect of Micro-arc oxidation time on coating was analyzed by metallographicmicroscope and scanning electron microscope. The growth of the time has little effect on thecoating composition, but the thickness of the coating was increasing and the surfacemicro-roughness was also increased.15min was chosen as the reaction time. After immersionin the simulation body fluid (SBF) which was used as lubrication in this research, theperformance of corrosion resistance of the micro-arc magnesium alloy WE43was the optimum, followed by untreated WE43magnesium alloy and magnesium alloy AZ41was worst.Microstructure analysis shows that corrosion cracks which on the surface of untreatedmagnesium alloy, was the incentive leading to the alloy corrosion. Micro-arc oxidation coatingcut off the contact of the magnesium alloy substrate and SBF, improving its corrosionresistance.Magnesium alloy hip joint friction and wear test was conducted by ring-block friction pairwith MMG-10atmosphere protective tester. The result shows that the friction coefficients ofartificial hip joint magnesium alloys WE43and micro-arc oxidation magnesium alloy coatingunder dry friction condition were stability, but both friction coefficients were higher; though acertain amplitude fluctuation in both friction coefficients under the condition of simulated bodyfluid lubricating was got, the friction coefficient is low; the friction coefficients of micro-arcoxidation magnesium alloy coating under both conditions were even lower, it can deduce thatthe micro-arc oxidation coating have anti-friction effects. SBF were involved in the friction andwear process in the lubrication condition, SBF corrosion accelerated the wear process of thematrix; micro-arc oxidation coating protected the substrate material and cut off from itsreaction with lubricant, the wear loss were less than that of untreated magnesium alloy WE43,the anti-wear effect of micro-arc oxidation coating was worked. Under the condition of SBFlubrication, the wear mechanism of magnesium alloys WE43was given priority to abrasivewear, corrosion wear was the complementary form during the whole wear process; the wearmechanism of micro-arc oxidation coating was only abrasive wear under the condition of lowload, but spalling wear coexist with abrasive wear under high loads.