A Study Of Preparation And Properties Of NbC And NbC_xN_1-x Coatings On TC4 Titanium Alloy Surface

Medical titanium alloys are widely used in the medical field because of their good properties,but harmful ions precipitated in the body due to friction and corrosion produce undesirable physiological responses to the body.Therefore,in this thesis,NbC and NbC_xN_1-x-x coatings were deposited on the surface of TC4 titanium alloy by RF magnetron sputtering to improve its mechanical properties,corrosion resistance and blood compatibility.In this thesis,we investigate the composition,cross-sectional morphology,and microstructure of the coatings by X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,multi-functional X-ray diffractometer?XRD?and transmission electron microscopy?TEM?.The mechanical properties of the coatings were characterized by the nanoindentation,scratch and friction test.The corrosion resistance of the coatings was characterized by electrochemical experiments,and the blood compatibility of the coatings was evaluated by the platelet adhesion test.Studies optimizes the preparation process of NbC coating by adjusting the substrate bias voltage.The SEM test results show that the thickness of the NbC coating decreases with increasing substrate bias.From the AFM test results,the surface roughness of the NbC coating decreases first and then increases with the increase of the substrate bias voltage.According to the results of XPS,it can be seen that the NbC coating is mainly composed of Nb-C bonds.According to the XRD and TEM results,it can be seen that the NbC coating prepared at-150V is composed of spherulites of about 7¹0nm,and the NbC coatings prepared under different substrate biases are face-centered cubic structures,and the coating exhibits a preferred orientation of?111?when the substrate bias is-150V and-200V,and the grain size of the coating reaches a maximum of 9.6 nm when the substrate bias is-150V.The results of the mechanical properties test show that the hardness,elastic modulus,friction wear resistance and film-based bond strength of the coating are all in the best state when the substrate bias is raised to-150V.The results of electrochemical experiments show that the NbC coating prepared with a substrate bias of-150V exhibits the best corrosion resistance.According to the blood compatibility experiment,when the substrate bias is-150V,the ratio of?_s^d/?_s^p is the smallest,the amount of platelet adhesion on the coating is the smallest,and the shape of platelets is regular.This studies through the adjustment of nitrogen and argon ratio to achieve NbC_xN_1-x-x coating preparation process optimization.SEM results show that the deposition thickness of the coating decreases with the increase of nitrogen-argon ratio,and the morphology of the coating is uniform and dense.AFM results show that the surface roughness of the coating is minimal at a nitrogen to argon ratio of 30:7.5.XPS experimental results show that the NbC_xN_1-x coating mainly exists as Nb-C bonded Nb-N bonds,and the content of N in the coating increases with the increase of nitrogen-argon ratio.XRD and TEM results show that when the nitrogen to argon ratio reaches 30:7.5,the face centered cubic Nb2CN phase is formed in the coating.When the ratio of nitrogen to argon reaches 30:7.5,a face-centered cubic Nb2CN phase is formed.Optimizing the nitrogen-argon ratio can significantly improve the mechanical properties of the coating,the nanohardness of the NbCxN1-x coating prepared at 30:7.5 nitrogen-argon ratio reaches 31.54GPa,and the NbC_xN_1-x coating exhibits higher wear resistance and bonding strength under this condition.Electrochemical experiments showed that the corrosion resistance of the coating was significantly improved when the ratio of nitrogen to argon was 30:7.5.