The Design Of Carbon-based Composite Film On Artificial Joint Surface And The Studies On Their Vacuum Plasma Preparation Process

Diamond-like carbon(DLC)film is a new type of carbon material,which has extremely high hardness and elastic modulus,ultra-low friction coefficient,and excellent wear resistance.However,the DLC film also has some problems that limit its practical application,such as poor toughness and large internal stress.Researchers have discovered that through the gradient superposition of films with different compositions and structures,such as metals,metal nitrides and DLC with higher sp² hybrid carbon,it can effectively reduce internal stress,improve the film-based bonding force of DLC films and Toughness,etc.Aiming at the shortcomings of the above DLC films,this paper prepares single-layer DLC films,double-layer DLC films,and Ti N/DLC multilayer films by using DC cathode arc and pulse cathode plasma arc dual excitation source vacuum evaporation technology and studys its composition,structure and mechanical properties,explore the effect of composite film modification the surface of artificial joints.The main contents of the research work are as follows:(1)Eight kinds of single-layer DLC films with different pulse frequencies(3Hz,10Hz)and pulse number(500?6000)were prepared.It is found that the increase of pulse frequency is accompanied by the decrease of sp²/sp³ ratio and the increase of surface roughness,which affected the mechanical properties of the film.At the same pulse frequency,the number of pulses also affects the surface morphology of the DLC film.As the number of pulses increases,the surface roughness of the film decreases first and then rises,which is related to the amount of particles evaporated during the deposition process and its diffusion,migration and growth.(2)Five kinds of double-layer DLC films were prepared(500_3Hz/3000_10Hz,10003Hz/300010Hz,30003Hz/300010Hz,40003Hz/300010Hz,60003Hz/300010Hz)by changing the pulse frequency and pulse number to design the film layer.The analysis found that with the same outer layer process,as the bottom 3Hz film pulse number increased,the change trend of the sp^2/sp³ ratio of the double-layer film was the same as that of the single-layer 3Hz film,which shows that the change of the pulse number of the 3Hz thin film at the bottom will affect the structure of the double-layer thin film.The film(1000_3Hz/3000_10Hz)showed the best comprehensive mechanical properties among the five samples,and was used as the superposition unit of the multilayer DLC film studied below.(3)The Ti N/DLC multilayer film was designed with Ti N as the bottom layer and DLC film as the outer layer.With the increase of the number of DLC superimposed units in the outer layer,the sp²/sp³ ratio of the film gradually decreases,while the Ra gradually increases.After reaching 3 superimposed units,the sp²/sp³ ratio and Ra of the multilayer film are stable,indicating that the structure of DLC film tends to be stable.In the hip joint simulation test,it was found that the wear loss of UHMWPE which rubbing with coated ball joint decreased by 30?33 mg when UHMWPE acetabulum rubs against uncoated Co Cr Mo alloy ball joint and ball joints with Ti N/DLC multilayer film.In addition,the multilayer film also effectively prevents the heavy metals Co and Cr from exuding in the ball,and the amount of exudation is only 1/3 of the uncoated sample.