| With the prolongation of human lifespan,the aging of the population and the increase of sports injuries,more and more patients need artificial joint replacement surgery due to joint damage such as knee joints and hip joints.Because Ti6A14V alloy combines high strength,good toughness,low specific gravity,good corrosion resistance,excellent biological inertness,and low elastic modulus,it is often used as artificial joint replacement material.However,the wear resistance of Ti6A14V material itself is poor,and the wear particles generated during the joint grinding process can lead to osteolysis and implant rejection.The preparation of diamond-like carbon(DLC)coatings with low friction coefficient,excellent wear resistance and good biocompatibility on the surface of medical Ti6A14V metal materials can not only induce the formation of bone bonding between bone tissue and the coatings,but also help improve the anti-wear and anti-friction properties and adverse biological reactions to metal wear debris.However,the low bonding strength of DLC coatings to medical metal material substrates will affect the long-term stability of DLC coatings in biological environments.Aiming at the problem of bonding strength of DLC coatings film base,this project starts from improving the physical bonding and chemical bonding interface between coatings film bases and proposes the research idea of Ti6A14V material surface texturing/carburizing to enhance the bonding strength of DLC coatings.The interface strengthening mechanism of the substrate surface texturing/carburizing DLC coatings film was revealed,the effect of texturing/carburizing composite effect on the friction and wear properties of the Ti6A14V substrate surface was deeply explored,and the friction reduction mechanism was analyzed.The main research contents are as follows:Firstly,micro-pits arrays were fabricated on the surface of Ti6A14V substrate by nanosecond laser.To study the effect of micro-pits on the bonding strength of DLC coatings on Ti6Al4V substrate and the effect of micro-pits themselves on friction and wear properties,a woven fabric was prepared.Textured samples(named T)with texture densities of 10%,20%,30%,and 40%.respectively.In addition,when the surface of Ti6A14V substrate was carburized,the laser power had the most significant effect on the formation of TiC phase.The laser power was increased from 20%to 100%in 10%increments,and the prepared carburized sample was named C,In this paper,the process of texturing/carburizing composite treatment is to first texture and then carburize.Carburizing is carried out on the surface of the prepared micro-pits material to obtain a composite microtextured/carburized composite.sample(named TC).For comparison,only mechanical polished sample(named O)was prepared.The substrate surfaces of the above-prepared samples were tested and characterized as follows:substrate surface hardness,elastic modulus,roughness,and wettability.Secondly,all the samples with different surface pretreatments were coated with DLC coatings and subjected to scratch experiments.The experimental results show that in the DLC coatings deposited on textured surface(named TDLC),the bonding strength of the micro-pits at 30%density is 8.72 N;in the DLC coatings deposited on carburized surface(named CDLC),the carburized sample with a laser power of 50%has a bonding strength of 9.18N.The DLC coatings deposited on texturing/carburizing surface(named TCDLC)has the highest bonding strength of 12.25N,and the DLC coatings deposited on only mechanical polished surface(named ODLC)used for the comparative experiment has a bonding strength of 5.73N.This shows that both texturing and carburizing alone can improve the bonding strength between the DLC coatings and the Ti6A14V substrate,and the texturing/carburizing combined treatment can significantly improve the bonding strength between the DLC coatings and the substrate.The mechanism of texturing/carburizing improving the bonding strength between DLC coatings and Ti6A14V substrate was analyzed from three angles of intercalation force,residual stress,and nucleation density at the interface.Finally,to analyze the friction-reducing and anti-wear mechanism of the combined effect of texturing/carburizing,316L stainless steel balls were selected as the countergrinding balls to conduct friction and wear experiments with the above-prepared samples under the condition of bovine serum albumin solution lubrication.The results of friction and wear experiments show that the friction and wear coefficient of ODLC is 0.46.that of CDLC is 0.4,that of TDLC is 0.17.and that of TCDLC is 0.11.This means that the combined effect of texturing/carburizing is the most significant in improving the tribological properties of DLC coatings. |
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