电解质等离子体抛光316LVM表面形貌及电化学特性

Surface Morphology and Electrochemical Characteristics of 316LVM Polished by Electrolytic Plasma

目的研究电解质等离子体抛光对316LVM植入物不锈钢表面形貌及其在磷酸缓冲盐溶液中的电化学特性的影响,解决复杂形状植入物表面抛光难题。方法原材料经线切割及表面预处理,制成20 mm×15 mm×3 mm的试验样件。对试样分别进行机械抛光及电解质等离子体抛光。机械抛光在砂带抛光机上进行,使用600、800、1200、2000、5000目的砂带逐级磨抛。电解质等离子体抛光中,电压为300 V,电解液为3%(质量分数)(NH4)2SO4水溶液,温度为85~90℃,抛光时间为15 min。通过粗糙度仪、扫描电镜,对试样表面粗糙度、微观形貌进行测试表征。通过能谱仪、X射线衍射仪,对试样表面元素含量、物相组成进行测试表征。通过电化学工作站,对磷酸缓冲盐溶液中的试样,进行电化学测试。结果电解质等离子体抛光后,试样表面粗糙度由初始的0.5μm降至0.089μm,试样表面机械加工痕迹被去除,平整光亮。机械抛光后,试样表面化学元素未发生明显变化,而电解质等离子体抛光后,试样表面的Fe、Cr含量升高。机械抛光表面的X射线衍射峰位置和强度未发生明显变化,电解质等离子体抛光后,在衍射角为43.5°处,衍射峰强度明显降低,在74.5°处,衍射峰强度明显升高,同时各峰的半高宽明显减小。在磷酸缓冲盐溶液中,机械抛光试样的自腐蚀电位由-0.252 V升高至-0.232 V,腐蚀电流密度由1.611μA/cm^(2)降低至0.5867μA/cm^(2),极化电阻由28.876 kΩ升高至64.682 kΩ。电解质等离子抛光试样的自腐蚀电位由-0.252 V升高至-0.214 V,腐蚀电流密度由1.611μA/cm^(2)降低至0.1582μA/cm^(2),极化电阻由28.876 kΩ升高到251.262 kΩ。结论电解质等离子体抛光可有效降低316LVM表面的粗糙度,提高表面平整度。电解质等离子体抛光后,表面Fe、Cr元素的含量升高,晶粒尺寸增大,呈(220)晶面择优取向。电解质等离子体抛光可提高316LVM在磷酸缓冲盐溶液中的耐腐蚀性能。

The aims of this study is to obtain the influence of electrolytic plasma polishing on the surface morphology of 316LVM implant stainless steel and its electrochemical characteristics in phosphate buffer solution and solve the surface polishing problem of complex shaped implants.After wire cutting and surface preprocessing,the raw materials were made into 20 mm×15 mm×3 mm test samples.The samples were polished by mechanical polishing and electrolytic plasma polishing respectively.Mechanical polishing was carried out on an abrasive belt polishing machine by using 600 mesh,800 mesh,1200 mesh,2000 mesh,and 5000 mesh abrasive belts and polished step by step.In the electrolytic plasma polishing,the voltage was 300 V,the electrolyte was 3wt.%(NH4)2SO4 aqueous solution,the temperature was 85~90℃,and the polishing time was 15 min.The surface roughness and micro morphology of the samples were tested by roughness meter and scanning electron microscope,the element composition and phase of samples were tested by energy dispersive spectrometer and X-ray diffractometer,and the electrochemical test in phosphate buffer solution was carried out by electrochemical workstation.The results showed that electrolytic plasma polishing reduced the surface roughness of the sample from 0.5μm to 0.089μm,the mechanical processing traces of the sample was removed,and the sample was smooth and bright.After mechanical polished,the chemical elements of the sample did not changed significantly,and the contents of Fe and Cr of the sample polished by electrolytic plasma polishing increased.The position and intensity of the X-ray diffraction peaks of mechanical polished samples did not changed significantly.After electrolytic plasma polishing,the intensity of the diffraction peak at the diffraction angle of 43.5°was significantly reduced and at the diffraction angle of 74.5°was significantly increased.At the same time,the FWHM of each peak was significantly reduced.The self-corrosion potential of mechanically polished and electrolytic plasma polished samples in phosphate buffer solution increased from-0.252 V to-0.232 V and-0.214 V,and the corrosion current density decreased from 1.611μA/cm^(2) to 0.5867μA/cm^(2) and 0.1582μA/cm^(2),the polarization resistance increased from 28.876 kΩto 64.682 kΩand 251.262 kΩ.It can be concluded that electrolytic plasma polishing can effectively reduce the surface roughness of 316LVM and improve the surface flatness.After electrolytic plasma polishing,the Fe and Cr element content increases,the grain size increases,and manifests the(220)crystal plane preferential orientation.Electrolytic plasma polishing can improve the corrosion resistance of 316LVM in PBS.