【作者】 姚忠平；

【导师】 姜兆华；

【作者基本信息】 哈尔滨工业大学 ， 应用化学， 2006， 博士

【摘要】 本文通过微等离子体氧化（MPO）方法在Ti-6Al-4V钛合金表面原位生长陶瓷膜,系统地研究陶瓷膜的相组成、微观结构及膜层耐腐蚀性能,并优化耐蚀性陶瓷膜层制备工艺;分析基体在MPO过程中的溶解现象和电解液中离子浓度变化特点,探讨电极表面陶瓷膜层生长规律和结构特点;研究膜层的等效电路、膜层结构与耐腐蚀性能的关系,并对优化工艺条件下制备的陶瓷膜层进行进一步的耐腐蚀性能测试和耐腐蚀机制研究。利用X-射线衍射仪（XRD）、扫描电子显微镜（SEM）、电子探针（EPMA）、能谱（EDS）和X射线荧光光谱仪（XRF）研究膜层的相组成、形貌和膜层内元素分布特点;利用加速的电化学方法初步评价膜层试样的耐腐蚀性能;通过电感耦合等离子体原子发射光谱仪（ICP-AES）分析基体元素在电解质溶液中的溶解和电解液中主要元素的变化特点;利用电化学阻抗谱（EIS）技术研究膜层电化学阻抗特性;由酸溶液中失重实验、接触腐蚀实验、盐雾腐蚀实验和高温氧化实验来考察膜层试样的耐腐蚀性能。研究表明Ti-6Al-4V钛合金在K₂ZrF₆电解液体系中MPO反应时形成含有m-ZrO₂、t-ZrO₂和磷酸锆盐相的陶瓷膜。膜层内钛元素很少,锆和磷元素很多。反应时间增加,磷酸锆盐成为膜内主晶相,膜层疏松、粗糙,截面裂纹较多。在NaAlO2溶液中微等离子体氧化钛合金,可以形成含有Al2TiO5、α-Al2O3和rutile TiO2相陶瓷膜层,其中Al2TiO5为主晶相。膜层具有双层结构:外层疏松,而内层致密、与基体结合很好。Ti元素在膜层的含量比基体低,并且外层含量比内层含量低。Al元素在膜层内含量远高于基体含量,并且在膜层中间部位含量最高。电参数的改变实际上改变了正负相脉冲的作用强度和作用时间,从而改变了膜层的相组成和结构特点。正向脉冲作用增加,有助于膜层内α-Al₂O₃含量增多、膜层增厚,但是膜层由于生长过快而较粗糙、多孔。负相脉冲作用增加有助于膜层内rutile TiO₂含量增多,膜层厚度下降,更加致密,但是由于致密性的提高往往导致膜层表面的微裂纹增多。反应时间增加,膜层厚度增加,表面粗糙度不断提高,晶相物质含量不断增多。铝酸盐体系制备的膜层结构更致密,耐蚀性好于锆酸盐体系。单脉冲MPO时,基体元素溶解的多少取决于电解质溶液中阴离子在电更多还原

【Abstract】 In this paper, the ceramic coatings were prepared in situ on Ti-6Al-4V alloy by micro-plasma oxidation （MPO）. The phase composition, microstructure and corrosion resistance of the ceramic coatings were studied in detail and the technology of corrosion resistant coatings was optimized. The dissolution of the substrate and the changes of the elements in the electrolyte during the MPO process were studied to discuss the growing characters and the structure of the ceramic coatings. The electric circuit model was established and the relation of the electric circuit model, the structure and the corrosion resistance was discussed. Further tests of corrosion resistance of the coatings under the optimized technology were carried out and the corrosion resistance mechanism was analyzed.The phase composition, morphology of the coatings was studied by X-ray diffraction （XRD） and the scanning electron microscopy （SEM）. The elements and the distribution characters were examined by electron probe microscopy （EPMA）, energy dispersive spectrum （EDS） and X-Ray Fluorescence Spectrometer （XRF）. The accelerated electrochemical methods （polarizing curve and potentiodynamic scanning） were used to evaluate the corrosion of the coated samples. The solution of the substrate and the elements in the electrolyte were measured by inductively coupled plasma-atomic emission spectrometer （ICP-AES）. Electrochemical Impedance Spectroscopy was used to analysis the relation between the structure and the corrosion resistance of the coated samples. The corrosion resistance of coated samples was assessed by acid corrosion resistance test of the coated samples, galvanic corrosion resistance, and salt spray corrosion test and high-temperature oxidation.The results show that the coating prepared on Ti-6Al-4V alloy by MPO in K₂ZrF₆ system is composed of m-ZrO₂, t-ZrO₂ and zirconium phosphate. Ti in the coating is low, while the content of Zr and P is much high in the coating. Increasing the reaction time, zirconium phosphate becomes the main crystalline of the coating. The coating surface is coarse, loose and two many cracks and micro-holes exist in the section image of the coatings. The ceramic coatings更多还原