TC4钛合金微弧氧化膜层制备及性能研究

发布时间：2018-02-04 07:07

本文关键词： TC4钛合金微弧氧化 C_3H_8O_3 结构耐蚀性　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：钛合金以其比强度高、生物相容性好等优点被广泛应用于航空、航天、医疗等领域,但耐磨性差、硬度低限制了钛合金的应用。微弧氧化技术为解决这些问题提供了一个很好的思路。本文选用应用最广泛的TC4钛合金为基体材料,研究工艺参数对TC4钛合金微弧氧化膜结构和性能的影响,为钛合金氧化膜投入产业应用提供一定的理论依据,拓宽钛合金的应用范围。本文采用恒定电流模式在Na2SiO3和Na3PO4为主盐的电解液中对TC4钛合金进行微弧氧化,研究了电流密度、氧化时间和Na2SiO3浓度对膜层结构和性能的影响。利用涡流膜层测厚仪、显微维氏硬度计分别研究了膜层的厚度和硬度,利用SEM、XRD、EDS研究了膜层的微观形貌、相组成、化学组成,利用电化学工作站研究了膜层的耐蚀性,利用球-盘摩擦磨损试验机和EDS研究了膜层的耐磨性能。在优选工艺参数的基础上添加C3H8O3,并利用上述设备研究了C3H8O3对膜层硬度、厚度、相结构、表面形貌和耐蚀性的影响。最后,本文结合试验结果对微弧氧化膜层形成过程进行了初步的探讨。实验结果表明:随着氧化时间增加,膜层的厚度不断增大,最大达到25.0μm,膜层表面粗糙度不断增大。随着电流密度和Na2SiO3浓度的增加,膜层都呈先变致密后变粗糙的趋势。厚度随电流密度的增大而增大,而随Na2SiO3浓度的增加呈先增大后减小的趋势。XRD图谱分析表明,增大电流密度和氧化时间使膜层中的金红石型TiO2含量增加,相比改变Na2SiO3浓度,能更明显地改变相组成。氧化时间由30min增加到40min,金红石型TiO2含量增加,硬度提高;氧化时间由40min增加到50min,膜层致密性降低,硬度降低。增大Na2SiO3浓度,硬度的趋势和增大氧化时间的相同。随着电流密度的增加,膜层硬度不断增大。随着氧化时间的增加,膜层硬度提高使耐磨性增强,当氧化时间为50min,膜层硬度降低、表面粗糙程度增加使耐磨性降低。增加电流密度,膜层的硬度和致密度增大,耐磨性提高,当电流密度增加到14A/dm2,膜层疏松层增加,耐磨性降低。增加Na2SiO3浓度,膜层表面的粗糙程度降低,耐磨性提高,当Na2SiO3浓度增加到6g/L时,膜层中的Na2SiO3含量升高,使粘着磨损加剧,耐磨性降低。膜层极化曲线分析结果表明,增大氧化时间,膜层的自腐蚀电流密度由7.62×10-7A/cm2减小到3.91×10-7A/cm2,后增大到6.82×10-7A/cm2,耐蚀性先增大后减小,增大电流密度表现出相同的规律。而随着Na2Si03浓度的提高,膜层自腐蚀电流密度由9.16×10-8A/cm2增大到1.72×10-7A/cm2,耐蚀性不断降低。增大C3H8O3浓度使膜层的硬度和厚度均表现出先增大后减小的趋势。从微观形貌可知,C3H8O3能够减轻尖端放电效应,防止膜层边缘被烧蚀。膜层的均匀性随C3H8O3浓度提高呈现先升高后降低的趋势。XRD图谱分析结果表明,C3H8O3并不能改变膜层的相结构。极化曲线分析结果表明,随着C3H8O3浓度的增大,膜层的自腐蚀电流密度由5.59×10-7A/cm2降低到2.54×10-8A/cm2,当C3H8O3浓度为6ml/L时,膜层的自腐蚀电流密度增大到2.43×10-7A/cm2,膜层的耐蚀性表现为先增大后减小。C3H803能够使膜层表面的含Si离子浓度增大,提供更多的放电中心,使膜层生长速度加快、致密度提高,改善膜层性能。但是,C3H8O3浓度过高,膜层性能下降。对试验数据进行多项式拟合,得出膜层生长动力学曲线:T=-4.577+1.322t-0.0148t2,并通过了 F检验和t检验。从曲线中可以得知:在微弧氧化膜层的生长过程中,生长速率不断下降。微弧氧化初始阶段,作用于膜层表面的电场强度大于1.26×108V/m,膜层阻挡层生长,当大于击穿电场时,开始起弧。起弧后,由于边缘位置具有更高的电场和界面能,发生边缘放电效应。从热力学的观点看,膜层中可能存在不饱和氧化物和AlPO4。
[Abstract]:Titanium alloy with its high specific strength, good biocompatibility and good etc. are widely used in aviation, aerospace, medical and other fields, but the poor wear resistance, low hardness limits the application of titanium alloys. Micro arc oxidation technology provides a good solution for solving these problems. This paper chooses TC4 titanium alloy is the most widely used as the matrix material, influence of process parameters on the structure and properties of TC4 titanium alloy by micro arc oxidation, provide a theoretical basis for the application of titanium alloy film industry investment, broaden the scope of application of the titanium alloy. This paper uses the constant current mode of microarc oxidation of TC4 titanium alloy based electrolyte salts in Na2SiO3 and Na3PO4, were studied effect of current density, oxidation time and Na2SiO3 concentration on the structure and properties of the coatings. The film thickness gauge using eddy current, film thickness and hardness, micro hardness were studied using Vivtorinox SEM, XRD, Study on the microstructure of EDS coating, phase composition, chemical composition, study on the corrosion resistance of the film prepared by electrochemical workstation, using a ball on disk tribometer and EDS on the wear resistance of the coatings. Adding C3H8O3 based on the optimum parameters of the equipment, and use of C3H8O3 on the hardness of the film thickness. Effect, phase structure, surface morphology and corrosion resistance. Finally, this paper combined with the test results of a preliminary study of the formation of the MAO coatings. The experimental results show that with the increase of oxidation time, film thickness increasing, the maximum reached 25 m, the surface roughness increases with the increase of current density and. The concentration of Na2SiO3, the film was rough trend becomes dense. First thickness increases with increasing current density, and with the increase of Na2SiO3 concentration of.XRD showed a trend of first increase and then decrease analysis Show that the increase of current density and oxidation time of the rutile TiO2 content in the film increases, compared to changes in Na2SiO3 concentration can significantly change the phase composition. The oxidation time increased from 30min to 40min, increased the content of rutile TiO2 hardness increased; oxidation time is increased from 40min to 50min, reduce the film density decreased and hardness. The concentration of Na2SiO3 increased, the hardness of the trend and increase the oxidation time. The same as the current density increases, the hardness increases. With the increase of oxidation time, the hardness to enhance wear resistance, when the oxidation time is 50min, the hardness decreased, the surface roughness increases the wear resistance decreased. The current density increases, the film the hardness and the density increases, the wear resistance increases, when the current density increased to 14A/dm2, the film layer is increased, the wear resistance decreased. The increase of Na2SiO3 concentration, the roughness of film surface reduction Low, the wear resistance increases, when the concentration of Na2SiO3 increased to 6g/L, increased Na2SiO3 content in the film, adhesion wear, wear resistance decreased. The film polarization curve analysis results show that the increase of oxidation time, the corrosion current density decreases from 7.62 * 10-7A/cm2 to 3.91 * 10-7A/cm2 film, then increased to 6.82 * 10-7A/cm2. The corrosion resistance increased firstly and then decreased with increasing the current density showed the same regularity. With the increase of the concentration of Na2Si03, the corrosion current density increased to 1.72 from 9.16 * 10-8A/cm2 * 10-7A/cm2, the corrosion resistance decreases with increasing C3H8O3 concentration. The film thickness and hardness showed first increased and then decreased from the micro. The morphology shows that C3H8O3 can reduce the discharge effect, prevent the film edge ablation coating uniformity. With the increase of C3H8O3 concentration of.XRD showed a trend of decrease after the first rise analysis results show that C 3H8O3 does not change the phase structure of the coatings. The polarization curve analysis results show that with the increase of C3H8O3 concentration, the corrosion current density by 5.59 * 10-7A/cm2 * 10-8A/cm2 film is reduced to 2.54, when the C3H8O3 concentration is 6ml/L, the coating corrosion current density increases to 2.43 * 10-7A/cm2, the corrosion resistance of the film was first increased after the decrease of.C3H803 can make the film surface containing Si ion concentration increases, providing more discharge, the film growth speed, improve the density and improve the film performance. However, the high concentration of C3H8O3, properties of the film decreased. Fitting the test data, the film growth kinetics curve: T=-4.577+1.322t-0.0148t2, and through F test and t test. We can learn from the curve: in the growth process of micro arc oxidation coating, the growth rate is declining. The initial stage of micro arc oxidation film, acting on the table The electric field intensity greater than 1.26 x 108V/m film, barrier layer growth, when more than the breakdown field, start arc. The arc, the edge position has higher electric field and the interfacial energy, the occurrence of edge effect. The discharge from the thermodynamic point of view, the film may exist in unsaturated oxygen complexes and AlPO4.

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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