TC4表面沉积Nb涂层在模拟体液环境下的电化学性能研究

Electrochemical Properties of Nb Coating on TC4 Substrate in Simulated Body Solution

利用双阴极等离子溅射技术在Ti-6Al-4V(TC4)合金表面沉积Nb涂层,采用XRD、XPS和SEM研究涂层的组成及横截面形貌,并采用电化学工作站对涂层与基体的电化学性能及其钝化膜半导体特性进行研究。电化学测试均在模拟人体体液环境的Ringer's溶液中37℃下进行。结果表明,Nb涂层厚度约为18μm,无孔洞、裂纹等缺陷,在(200)晶面呈现择优取向。涂层表面钝化膜成分主要为Nb_(2)O_(5)。相比TC4基体,涂层具有更高的开路电位EOCP、腐蚀电位Ecorr和更低的腐蚀电流密度Icorr;涂层与基体合金试样均表现出单一容抗弧,但涂层具有更高的阻抗和较低的有效电容值;两种试样的钝化膜均表现出n型半导体特性,在不同的成膜电位Ef下,Nb涂层的钝化膜具有更低的平带电位Efb,施主密度Nd和扩散系数D0。

To improve the corrosion resistance of Ti-alloy applied to human implants,Nb coating was deposited on the surface of Ti-6Al-4V(TC4)alloy by double cathode plasma sputtering technique.The composition and the cross-sectional morphology of the coating were characterized by XRD,XPS and SEM.The electrochemical properties of the coating and the semiconductor properties of the passivation film for the coating and the substrate were studied in Ringer's simulated body solution at 37℃by electrochemical workstation.The results show that the Nb coating exhibits a preferred orientation on the(200)crystal plane,and the coating thickness is about 18μm without defects such as holes and cracks.The passive film on the Nb coating is mainly Nb_(2)O_(5).Comparing with the TC4 substrate,the coating has higher open circuit potential(EOCP),corrosion potential(Ecorr)and lower corrosion current density(Icorr).Both of the TC4 alloys with and without Nb coating exhibit a single capacitance loop,however,the coated alloy exhibits higher impedance and lower effective capacitance rather than the substrate.The passivation films of two samples exhibit n-type semiconductor characteristics.By different formation potential(Ef),the flat band potential(Efb),the donor density(Nd)and diffusion coefficient(D0)of the passivation film on the coating are always lower than that on the bare TC4 alloy.