Composite Texturing Substrate Surface And Ternary Nanoparticle-doped Hydroxyapatite Coating Properties

Research on artificial implant materials and preparation methods has been driven by the progress of society and the increasing demand for high-quality hard tissue replacement materials.Hydroxyapatite(HA)ceramics resemble the inorganic material of human bone very closely and have been frequently used in medical applications such as artificial joints,dental implants,and bone repair in the form of coatings.The plasma spraying(PS)process allows the exceptional mechanical properties of the metal matrix to be exploited with the good biocompatibility of HA.However,HA coatings still suffer from poor mechanical properties,insufficient bonding strength,and osteoinductive ability,which have limited their application in the field of biomedical materials.To address the aforementioned issues,the paper researches the aspects of coating preparation,coating-substrate bonding interface design,and composite modification of micro-nano particles.The main research content is as follows.(1)The pretreatment method of composite texturing surface that induces strong bonding of the coating on the substrate surface is proposed.This study focuses on the selection of plasma spraying process parameters and the design of the bonding interface.The impact of the spraying process on the interface characteristics of HA coatings was investigated.The composite texturing substrate surface was designed by combining conventional blasting,ultraviolet laser texturing,and ultrasonic acid etching processes.The interaction law of each processing step and the characteristics of the pretreated surface during the preparation of the composite texturing surface were analyzed.The results show that the increase in spraying power facilitates the effective deposition of molten droplets,the tight bonding of the coating-substrate interface.and the formation of a uniform flat structure of molten droplet units.The optimal spraying process parameter scheme obtained is:spraying voltage 65 V,spraying current 550 A,and spraying distance 120 mm.In the preparation of composite texturing surfaces,the texture width is positively correlated with the number of laser processing passes and offsets,and negatively correlated with the number of scans.The increase in blasting pressure aggravates the substrate damage and affects the morphology of subsequent laser-processing textures.Laser texturing and ultrasonic etching processes can remove contaminants from the substrate and optimize the roughened surface of the substrate.The final selection of laser processing offset is 5 μm,blasting pressure is 0.2 MPa.Within the prepared composite texturing pre-treated surface,the boundary between the blasting and texturing parts is well-defined and a work-hardened area of about 150 μm in-depth exists.As the number of laser scans increases,the microgroove depth and surface roughness of the substrate shows an upward trend overall,and the sectional morphology of the micro texturing changes from a disc shape to a cone shape,and then to a columnar and column-like shape.(2)The bonding mechanism and failure behavior of HA coatings on grooved composite texturing substrate surfaces with different parameters were investigated.The bonding form of the coating on the composite texturing surface is dominated by stronger embedded and occluded bonds,which enhances the anchoring of the HA coating.Meanwhile,the microgroove morphology increases the substrate surface roughness,interfacial contact area,and adhesion sites,which weakens the stress concentration effect to facilitate the stacking deposition of molten droplets and reduce the coating porosity.As a result,the bonding strength of the coating on the composite texturing surface is significantly stronger than that of the blasting and texturing single-treated surfaces.The average tensile strength increased by 29.5%and the shear strength increased by 26.6%compared to the grit blasting surface.The average tensile strength of the coatings on the composite texturing surface increased by 67.7%and the average shear strength increased by 160.7%compared to the only texturing surface.The tensile strength of the coating and the degree of damage showed a tight relationship,and the coating on the conical texture surface exhibited the highest tensile strength of about 45.94 MPa in this experiment.In particular,the microgroove texture surface with a depth-to-width ratio near 0.65 facilitates the improvement of the tensile properties of the coating.The coatings exhibit cohesive failure by shear,and the importance of the factors affecting shear strength is ranked as follows:bonding form>interface morphology>coating porosity,where the columnar texture interface is beneficial to enhance the shear resistance of the coatings.(3)HA coatings doped with SiO2,Gd2O3 and CeO2 ternary nanoparticles were developed to improve the service performance.In each powder formulation,nanoparticles uniformly adhere to the surface of HA powder.Each doping component is uniformly distributed in the prepared spray coating,and the original material characteristics are well preserved.With the progressive addition of each nanoparticle,the surface of the composite coating becomes rougher,and the bonding performance is enhanced.Among them,the ternary-doped HASiGdCe coating increased the bonding strength by 55.16%compared with the HA coating,and its surface was able to induce the formation of a bone-like apatite layer with good in vitro biological activity.Meanwhile,the presence of multiple nanoparticles promoted MC3T3-E1 cell proliferation,enhanced alkaline phosphatase activity,type I collagen secretion,and extracellular matrix mineralization levels.The results demonstrated that the ternary-doped HASiGdCe coating exhibited good mechanical properties,bioactivity,cytocompatibility,and the ability to promote osteogenic differentiation.