退火对钛合金钽涂层力学及生物性能的影响

Effect of Annealing on Mechanical and Biological Properties of Titanium Alloy Tantalum Coating

目的 针对钛合金(TC4)在骨植入、骨替换方面因受体液腐蚀及骨骼之间的相互摩擦使改性涂层容易遭受破坏导致有毒金属离子的释放,通过退火提高TC4表面钽涂层的力学性能和生物相容性能。方法 采用磁控溅射技术在TC4基体上沉积钽涂层,并在不同的热处理温度650、750、850℃下退火5 h,使用扫描电子显微镜、能谱仪、XRD、划痕仪、摩擦磨损试验机、电化学工作站和生物毒性实验对Ta涂层的组织形貌、力学性能及生物性能进行测试与表征。结果 所制备的Ta涂层组织较致密,在一定的退火温度下,组织结构变得更加致密。在退火温度650℃时的硬度值(16.68 GPa)和弹性模量值(208.90 GPa)最高,这是由于产生较强的β-Ta峰,使硬度值显著提高。经750℃退火后,涂层具有最大的结合强度(20.82N),优异的耐腐蚀性,摩擦曲线波动最小、最平稳且平均摩擦系数值(COF)最小。这是由于涂层与基体之间的元素相互扩散,降低了界面应力,促进了结合强度的提高。这有利于提高涂层的致密度,可降低涂层表面的微孔缺陷,阻碍腐蚀溶液通过涂层的路径作用,从而提高基体的耐腐蚀性。同时有效避免了涂层大面积脱落,减少了摩擦表面积,也提高了涂层的摩擦性能。在750℃和850℃退火温度下钽涂层的KRGR>80%,表现出良好的生物相容性。结论 经退火后的钽涂层组织更加致密,结合强度更高,耐磨性、耐腐蚀性、生物相容性更好。

The work aims to solve the problem that the modified coating of titanium alloy(TC4) is easily damaged due to the corrosion of body fluids and the friction between bones in bone implantation and replacement,which leads to the release of toxic metal ions,tissue and cell necrosis,thus causing the failure of implantation.The mechanical and biological properties of tantalum coating on the surface of TC4 can be improved by annealing process.In this study,TC4 titanium alloy with the size of ? 25 × 2 mm was selected as the matrix,which was ground to 2000# with sandpaper.Ta coating was deposited on the surface of TC4 matrix by magnetron sputtering technology,and annealed at different heat treatment temperature of 650,750 and 850 ℃ for 5 h.The cross section morphology,composition distribution,phase structure,bonding strength,wear resistance,corrosion resistance and biocompatibility of Ta coating were tested and characterized by scanning electron microscope(SEM),energy dispersive spectrometer(EDS),X-ray diffraction(XRD) scratch instrument,multi-functional high temperature friction and wear testing machine,electrochemical workstation and biotoxicity test.The microstructure of the prepared Ta coating was relatively dense,and became denser at a certain annealing temperature without obvious micropores.The hardness value(16.68 GPa) and elastic modulus value(208.90 GPa) at the annealing temperature of 650 ℃ showed the highest performance,which was due to the generation of strong β-Ta peak,improving the hardness value significantly.After annealing at 750 ℃,the coating had the maximum bond strength(20.82 N),the excellent corrosion resistance,the smallest fluctuation of the friction curve,the most stability and the lowest average coefficient of friction(COF) value.This was due to the mutual diffusion of elements between the coating and the matrix,which reduced the interfacial stress and promoted the increase of bond strength.This was beneficial to improving the density of the coating,reducing the microporous defects on the coating surface,hindering the corrosion solution through the coating path action,thus improving the corrosion resistance of the matrix.At the same time,it effectively prevented the large area of the coating from falling off,reduced the friction surface area,and improved the friction performance of the coating.The RGR of tantalum coating at 750 ℃and 850 ℃ a nnealing temperature was >80%,showing good biocompatibility.In conclusion,the annealing process significantly improves the mechanical and biological properties of the coating.After annealing at different temperature,the microstructure of the coating is more compact and uniform,the hardness value and bond strength are higher,and the wear resistance,corrosion resistance and biocompatibility are better.