Microstructure And Properties Of Metal Oxide Coating By Magnetron Sputtering

Recently,metal oxide ceramic coatings have become the hot materials for modifying medical implants because of their excellent anti-corrosion,anti-wear,and biocompatible performance.In this thesis,four metal oxide coatings of Ta₂O₅,Nb₂O₅,Zr O₂,and Ti O₂and three Ta₂O₅based coatings of a monolayer,composite,and gradient structure were prepared on medical TC4 titanium alloy by magnetron sputtering.The preparation,microstructure,and properties of the layers were systematically studied.The finite element method was employed to analyze the residual thermal stresses of four oxide coatings and three Ta₂O₅based coatings on the TC4 surface.The outcomes reveal that the order of the maximum residual stress in the four oxide coatings is Ti O₂（1.03 MPa）<Zr O₂（10.2MPa）<Nb₂O₅（19.7 MPa）<Ta₂O₅（32.2 MPa）.With the increase in coating thickness,the Nb₂O₅layer shows an enhanced maximum stress,whereas the one for the Ta₂O₅,Ti O₂,and Zr O₂coatings reduce first and then augment.When the total thickness of the coating was 4μm,the maximum residual thermal stress of Ta₂O₅gradient coating is 27.5 MPa,which is 15.4%and 8.9%lower than that of monolithic and composite coating,respectively.The microstructure and properties of the four kinds of oxide coatings were investigated on the TC4 surface by magnetron sputtering.The outcomes show they exhibit columnar growth mode,in which Ta₂O₅,Nb₂O₅,and Ti O₂coatings have an amorphous structure,and Zr O₂layers have a tetragonal phase.The order of adhesion of the coating from large to small is Ti O₂（over 50 N）>Zr O₂（20.32 N）>Nb₂O₅（3.442 N）>Ta₂O₅（1.91 N）.Ti O₂coating has a wear rate of 16.45×10^-5mm³N^-1M^-1,21%,25.6%,and 31.8%lower than Ta₂O₅,Nb₂O₅,and Zr O₂coatings,respectively.In contrast,Zr O₂coating shows the best anti-corrosion performance,followed by the Ta₂O₅and Nb₂O₅coating,and Ti O₂coating has the worst corrosion resistance.The microstructure and performances of the three Ta₂O₅based coatings were evaluated on the TC4 surface via magnetron sputtering.The results show that the layers have the columnar growth mode with an amorphous structure.Gradient coating exhibits the slightest surface roughness and the best hydrophilicity,followed by composite and single-layer coating.Gradient coating has an adhesion of 25.81 N,which is 21 times and 0.64 times higher than monolayer and composite coating,respectively.Gradient coating has the highest H and H³/E²values,32.9%and 72.1%higher than the monolayer coating.The wear rate of the gradient coating is 3.57×10^-5mm³N^-1M^-1,which is 78%and 34.3%lower than the single-layer and composite coatings,respectively.With a thicker Ta₂O₅layer and a lower Ti content on the surface,the coating shows a better corrosion resistance.The corrosion protective effects of monolithic,composite,and graded coating on TC4 were 99.5%,68.6%,and 53.4%,respectively.