模拟体液中医用钛合金阳极氧化膜的摩擦行为

Tribological Behavior of Anodic Oxide Film on Titanium Alloy in Simulated Body Fluid

目的 在TC4钛合金表面获得阳极氧化膜,分析阳极氧化膜膜厚随电压变化的规律,探讨阳极氧化膜在模拟体液中的摩擦性能。方法 用强硫酸型溶液作为电解液,利用氧化还原反应,用自制的设备在TC4钛合金表面以不同的电压进行阳极氧化,在试样表面制得颜色各异的氧化膜。使用多功能材料CFT–1型表面综合性能测试仪,对阳极氧化膜在模拟体液中进行摩擦性能测试。结果 阳极电压从15 V增大到100 V,氧化膜厚度从6.2μm增大到28.4μm,平均摩擦因数先增大后减小。电压升高,Rutile TiO在阳极氧化膜的含量不断提高。氧化膜在模拟体液中的摩擦行为分为3个过程,第一阶段,各种电压的TC4合金氧化膜均在前5 min完成短时跑和;第二阶段,摩擦因数震荡上升,随着电压的升高,氧化膜磨粒磨损加剧,局部出现剥落,75 V的剥落最大,100 V的磨痕比较平整;第三阶段,摩擦因数再次爬升,15、35、60 V出现在36 min时,75 V出现在40 min时,100 V在48 min时,阳极氧化膜被磨穿。结论 氧化膜的颜色、耐磨性、物相及表面形貌受电压影响。钛合金阳极氧化膜在模拟体液中耐磨性良好,磨损类型为磨粒磨损。

Titanium alloy has been widely used in aerospace, weapon equipment, medical and other fields because of its good corrosion resistance, light weight and high specific strength. TC4 titanium alloy has good biocompatibility and unique shape memory and hyperelasticity. Its elastic modulus is closest to the elastic modulus of human bone among the existing biological alloy materials. It has been widely used in human hard tissue repair operations such as artificial joint, bone repair, broken bone joint and so on. The main research content of this experiment is to obtain anodic oxide film on the surface of TC4 titanium alloy,analyze the variation law of anodic oxide film thickness with voltage, and explore the friction performance of anodic oxide film in simulated body fluid.The anodizing experiment adopts a self-made oxidation device, which is mainly composed of constant voltage and constant current MP2002D power supply, electrolytic cell, stirring system and cooling system. The self-made electrolyte consists of sulfuric acid, phosphoric acid, hydrofluoric acid and deionized water in a specific proportion. The anodic oxidation is carried out in the self-made electrolytic solution. The anode is made of TC4 medical titanium alloy, and the cathode is made of stainless steel plate. The distance between the two poles is maintained at more than 5 cm. The pulse voltage is applied with 15 V, 35 V, 60 V, 75V and 100 V respectively, and the pulse frequency is 550 Hz. The temperature of the electrolytic solution is maintained at 20 ℃through the cooling device for 3 min. The oxide films of different colors are obtained by sampling. XRD and SEM experiments were used to analyze the phase structure, film thickness and microstructure of the anodic oxide film. The friction properties of the anodic oxide film in simulated body fluid were tested by CFT-1 surface comprehensive performance tester.The experimental results show that the thickening rate of anodic oxide film of titanium alloy is gradually uneven with the increase of voltage, β Phase titanium gradually becomes bald and fades, α The pit becomes more and more obvious, resulting in βPhase harmony α The pore size of the oxide film increases with the change of phase concavity and convexity;When the anode voltage increases from 15 V to 100 V, the oxide film thickness increases from 6.2 μm increased to 28.4 μm. At the same time,through the phase analysis experiment, it is found that the content of rutile TiOin the anodic oxide film increases continuously with the increase of voltage, which shows excellent properties in hardness, density and dielectric constant;Therefore, with the increase of voltage, the anodic oxide film will have better surface properties. Through the friction experiment, it is found that the friction behavior of oxide film in simulated body fluid is divided into three processes. In the first stage, TC4 alloy oxide film with various voltages completed short-time running and running in the first 5 minutes. In the second stage, the friction coefficient fluctuates and rises. With the increase of voltage, the wear of oxide film abrasive particles intensifies, and local spalling occurs.The spalling of 75 V is the largest, and the wear mark of 100 V is relatively flat. In the third stage, the oxide film friction coefficient of each voltage climbs again at different times, 15 V, 35 V and 60 V at 36 min, 75 V at 40 min and 100 V at 48 min. At this time, the anodic oxide film is worn through.The anode voltage will affect the color, thickness, surface morphology, phase and wear resistance of the oxide film. The higher the voltage, the darker the color, the higher the thickness and the stronger the wear resistance of the oxide film. The results of friction in simulated body fluid show that with the increase of anode voltage, the friction coefficient of oxide film first increases and then decreases;The anodic oxide film of titanium alloy has good wear resistance in simulated body fluid, and the wear type is abrasive wear.