Researches On Biotribology Properties Of Carbon-based Composite Films Prepared By Vacuum Plasma

Diamond-Like Carbon(DLC)films are a type of carbon-based hard films with extremely high hardness and elastic modulus,excellent wear resistance,low friction coefficient and good biocompatibility.In order to solve the problems such as large internal stress and low adhesion of DLC films,composite structures such intermediate and gradient layers are designed,which effectively improved the comprehensive performance.In recent years,DLC films have shown broad application potentials in biotribology.They can effectively prevent the exudation of metal ions and improve the wear resistance of joint prostheses.However,there is not enough research on DLC films using joint simulation testing machines,and the theory of in vitro evaluation experiments is incomplete.In this paper,Ti N films and Ti N/Ti/DLC multilayer composite films were prepared by the dual excitation source system consisting of DC cathodic arc and pulse cathodic plasma arc.The composition and structural characterization and the measurements of the tribological properties on different joint simulation test machines were conducted.The main contents of the work are as follows:(1)Ti N films and Ti N/Ti/DLC multilayer composite films were prepared.It is found that the roughness(Ra)of Ti N/Ti/DLC multilayer films is 27.6% lower than that of Ti N films,and the adhesion of Ti N/Ti/DLC films is also better obviously.The results of tribological measurements showed that the friction coefficients of Ti N/Ti/DLC films in different liquid media are all around 0.1 and for the ones of Ti N films in calf serum solution,they reach 0.2,which are maintained between 0.6 and 0.7 in other conditions.(2)The tribological behavior of the friction pairs including Ti N/Ti/DLC multilayer films and ultra high molecular weight polyethylene(UHMWPE)is studied using a pendulum friction tester in the joint swing motion mode.The effects of different liquid media(calf serum,sodium hyaluronate,chondroitin sulfate,artificial lubricating fluid containing cholesterol liquid crystal)on the tribological properties of friction pairs were studied.The friction pairs in the artificial lubricating fluid containing cholesterol liquid crystal show the best lubricating performance and the friction coefficient is 0.085.According to the tribological measurements in sodium hyaluronate solutions with different concentrations,the higher the concentration,the higher the friction coefficient of the films.(3)Applying UHMWPE as sockets,the Co Cr Mo alloy joint balls modified by Ti N/Ti/DLC multilayer films were subjected to 5 million cycles of friction test in a hip joint friction simulation test machine.The wear debris morphology,p H value of the media and release amount of harmful metal ions after different cycles were analyzed.The morphology of most wear debris is spherical.The Ti N/Ti/DLC multilayer films can effectively reduce the amount of wear debris,and the wear amounts of the UHMWPE sockets represent a decrease between 340 mg and 360 mg.Besides,the exudation of harmful metal elements(Co and Cr ions)is only 25.4%?50.6% of that of the untreated ball head.