【作者】 汪景奇；

【导师】 苏勇； 王建民；

【作者基本信息】 合肥工业大学 ， 材料加工， 2009， 硕士

【摘要】 微弧氧化技术是一项具有较大潜力和广阔应用前景的表面改性新技术,在航空、航天领域有重要的应用背景和价值。为了在Ti-6A1-4V合金表面获得良好的氧化膜层,本文采用直流稳压电源微弧氧化设备进行了NaOH、Na₂SiO₃、Na₂HPO₄三种电解液体系中的微弧氧化试验,并优选出最佳工艺参数。利用XRD、SEM、EDS等手段对涂层的微观组织结构进行分析,研究了涂层的形成机制,并测试了涂层的厚度、硬度和耐腐蚀性。以及电解液浓度和初始温度对微弧氧化的起弧电压变化规律的影响。在Na₂HPO₄和Na₂SiO₃溶液作为电解液时,起弧电压都是随着电解液浓度、初始温度的升高而线性减小。当浓度过小时,在阳极钛合金板的边缘易发生烧损现象;当电解液浓度过大时,阳极钛合金板不易起弧;在Na₂HPO₄和Na₂SiO₃溶液作为电解液时,在不同的处理时间、电解液浓度和电压下制备的微弧氧化膜表面都呈现多孔结构。随着微弧氧化时间的延长,氧化膜的厚度不断增加,而生长速率和耐腐蚀性先增加后减小,表面粗糙程度、硬度和微孔尺寸逐渐增大,微孔密度逐渐减小。膜层主要由锐钛矿和金红石型TiO₂组成;随着微弧氧化时间、电解液浓度和电压的增加,膜层中锐钛矿型TiO₂逐渐减少,而金红石型TiO₂则逐渐增多并最终在膜层中占据主导地位;在NaOH电解液中,氧化膜表层质量随着添加剂NaF的浓度增加而变的更加光滑,膜层厚度和耐腐蚀性随着添加剂NaF的浓度的增加都在逐渐增加。虽然微孔尺寸逐渐增大,微孔数目也在逐渐减少,但其耐腐蚀性却在逐渐增大。这与上述两种电解液中制备的微弧氧化膜性能不尽相同,所以一定程度上,在含有添加剂NaF的NaOH溶液中所生成的氧化膜层更具有耐腐蚀性;实验确定的最佳测定条件:在含有添加剂NaF的NaOH溶液中,电解液浓度为3g/LNaOH +0.4mol/LNaF,微弧电压为280V,氧化时间为10min;在Na₂HPO₄溶液中,电解液浓度为0.3mol?L,微弧电压为180V,微弧氧化时间为300s,电解液初始温度为10℃;在Na₂SiO₃溶液中,电解液浓度为50g?L,电解液初始温度为20℃,微弧电压为280V,微弧氧化时间50s-150s为宜。这样可以得到孔径大小均匀而且致密性较好的氧化膜。综上所述,欲制备理想的微弧氧化膜就必须综合考虑各种因素的相互作用。更多还原

【Abstract】 As a novel technology of surface modification, Microarc Oxidation（MAO） has great potential and abroad application prospect. It has important application background and value in aerospace and aviation fields.In order to obtain a good oxidation coating on surface of Ti-6A1-4V alloy,NaOH、Na2SiO3 and Na2HPO4 coatings were Prepared in the corresponding electrolyte system by micro-arc oxidation （MAO） method,and the optimal MAO parameters were obtained by using direct current constant voltage electrical source. Microstructure of the coatings was characterized using XRD, SEM and EDS techniques. The formation mechanism of MAO coating was investigated. The thickness, rigidity and anti-causticity of coatings were tested. The influence of electrolyte concentration and temperature was discussed to the variational disciplinarian of sparking voltage. As the result of research as follows:When Na2HPO4 and Na2SiO3 solution were choosed as electrolytic solution, the magnitude of sparking voltage minish linearly with the hoist of electrolytic solution and initial temperature. when the concentration was very small, the adust phenomenon took place easily on the edge of nodic titanium alloy board; by contraries, sparking was found difficultly.When Na2HPO4 and Na2SiO3 solution were choosed as electrolytic solution, micro-arc oxidation coatings had the porous structure in different disposal time、electrolytic solution concentration and voltage. The rigidity、thickness、surface roughness and size of tiny hole augment of coating increased gradually, growth velocity and corrosion resistance increased primitively and then minish, but density of tiny hole decreased gradually. The results show that anatase and rutile titania on the titanium surface mostly. Anatase titania droped off and rutile titania increased gradually, which will play a leading role.The quality of oxidation film became more velveter with increase of NaF concentration. Thickness of film and rigidity increased gradually with increase of NaF concentration. Although pore size increased and the number of microporous decreased gradually, corrosion resistance increased gradually, the performance of oxidation film mentioned above two kinds of electrolyte was not the same, so the corrosion resistance of oxidation film was more better to a certain degree in NaOH solution Containing additive NaF.Through the test, the optimized working conditions are determined: electrolyte concentration is 3g/L NaOH +0.4mol/LNaF, micro-arc voltage is 280V, oxidation time is 10min in NaOH solution Containing additive NaF; electrolyte concentration is 0.3mol?L, micro-arc voltage is 180V, oxidation time is 300s, initial temperature of electrolyte is 10℃in Na₂HPO₄ solution; electrolyte concentration is 50g?L, micro-arc voltage is 280V, oxidation time is 50-150s, initial temperature of electrolyte is 20℃in Na₂SiO₃ solution; Like this, oxidation film of homogeneous pore size and good compactness can be obtained.In a word, to prepare perfect micro-arc oxidation film, interreaction of various factors must been taken into account.更多还原