| Ti6Al4V alloy has been widely applied for orthopaedic implants because of its excellent biocompatibility,good anti-corrosion property and outstanding fatigue resistance.In addition,its elastic modulus is close to that of human cortical bone.However,Ti6Al4 V alloy can release Aluminum ions and Vanadium ions into human’s body,which would affect body adversely.Consequently,it can result in a series of malignant tissue reaction.Besides,as Ti6Al4 V alloy has no biological activity,it just mechanically combined with bone organization.To some extent,the combination will become loose after a surgery.On the other hand,hydroxyapatite(HA),with its excellent bioactivity and biocompatibility,can effectively improve the mechanical properties and biological activity of Ti6Al4 V alloy when using it on Ti6Al4 V alloy surface.However,it is worth noting that HA coating always has some big pores.It is unable to effectively restrain the overflow of Al,V elements and the erosion of body fluids on substrate.This paper adopts the concept of “biological inert material + bioactive material” to deposit coating,which makes it has both excellent biological activity and ion shielding property.The inert diamond-like carbon(DLC)coating is prepared as a transition layer between HA coating and Ti6Al4 V substrate with its pyknotic structure and good corrosion resistance,which can significantly improve the application reliability of Ti6Al4 V alloy.In this paper,HA coatings under different technological parameter were deposited on the Ti6Al4 V alloy surface by using the RF magnetron sputtering technology.The influence of sputtering conditions,annealing,HA structure,composition and microscopic morphology were studied by using FTIR,XRD,SEM and AFM etc.Then,the results were used to analyses the influence of sputtering conditions and annealing on the nano-mechanical properties,bonding strength,wettability and corrosion resistance and biodegradability on HA coating.Thus,optimal process parameter of HA coating can be obtained after comprehensive analyses.Under this condition,the HA/DLC biological composite coating is prepared.Raman spectroscopy was used to analyze the structure of DLC transitional layer,in order to figure out the difference of nano-mechanical properties,bonding strength,wettability,corrosion resistance and biodegradability between a single HA coating and HA/DLC composite coating.The results revealed that the HA coating,which is deposited by using RF-MS technology,has compact structure and excellent surface quality.The influence of annealing treatment on HA coating including: restoration of the missing hydroxyl,significantly increased crystallinity,decreased defects and increased grain size and roughness,which improve the nano-mechanical property and biodegradability of HA coating.In addition,the value of HA coating’s contact angle decreased,which is much more close to that of the cell adhesion angle.HA coating’s crystallinity is obviously improved with the improvement of negative bias.What’s more,the surface and interface defects of HA coating reduced,the bonding strength between HA coating and substrate became strong and HA coating’s grain size decreased.Therefore,the mechanical properties increased.The roughness of HA coating surface decreased,which is not conducive to induce bone growth.Although biodegradability of HA coating decreased,the value of contact angle was improved to that of cell adhesion.The increase of HA coating’s density can prevent fluid from infiltrating to substrate,thus to improve the corrosion resistance of HA coating.Besides,the variation of power has a little effect on HA coating’s crystallinity.When power is 250 W,the structure and property of HA coating is optimal,which means its particle size distribution is most uniform and it has the least defects in surface and interface.Meanwhile,it has the maximal bonding strength,most excellent nano-mechanical property,good corrosion resistance and biodegradability.HA coating’s contact angle value is close to that of cell adhesion angle under annealing treatment.It is found that HA coating’s optimum preparation process parameter is the power with 250 W and negative bias with-100 V,and we use this process conditions to deposit DLC/HA composite coating on Ti6Al4 V alloy surface.Raman spectra shows that the ratio of sp~3 bond and sp~2 bond in DLC transition layer is 0.88.Hence,DLC transition layer shows high hardness as well as good lubrication property.DLC has uniform particles and compact structure from AFM figure,so it has good ion shielding property.DLC/HA composite coating has more excellent properties than HA coating,including mechanical properties,bonding strength,wear resistance,corrosion resistance and ion shielding property. |
PDF Full Text Request