后处理方式和纳米氮化硅对钛表面磷酸盐转化膜物相结构与性能的影响

发布时间：2018-02-02 10:32

  本文关键词： 钛及钛合金 磷酸盐 转化膜 纳米氮化硅 后处理方式　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：磷酸锌转化膜广泛应用于金属表面的防腐、提高涂装层结合力和表面润滑等方面。同时,钛因具有高比强度、无磁性、稳定性好等许多优异性能而在国民经济中的作用越来越大。但钛表面由于存在易氧化、对黏着磨损敏感、对涂层附着力差等缺陷而限制了其应用。本文利用易于实现的常温化学转化方法在钛(TA2)表面制备磷酸锌转化膜。通过讨论前处理工艺、基础转化工艺参数和后处理工艺等因素,并通过添加纳米Si_3N_4颗粒,确定了一种在常温条件下在钛表面制备纳米复合磷酸盐转化膜的工艺配方。分别利用X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、声发射划痕仪及三电极电化学工作站等手段对转化膜的物相、微观形貌、力学性能及耐蚀性能进行了系统的表征和分析。结果表明,转化膜主要有四水磷酸锌(Zn3(P04)2·4H20)组成,工艺条件对转化膜物相种类影响不大。碱洗除油、酸洗和表调对转化膜的影响是互相不可替代的,是制备完整的高质量转化膜的前提。转化时间和转化温度对转化膜物相影响较小,在25℃和75℃温度分别制备的转化膜膜厚相差较大,而结合力和耐腐蚀性能相差不大。在0.5-10 min内,随着转化时间延长,转化膜晶粒尺寸变大,数量增加,晶粒形状由单一薄片状向粗糙板条状变化,逐渐形成致密和均匀的转化膜。不同清洗干燥次序对化学转化膜的微观形貌及耐腐蚀性能有明显的影响,先干后洗制备的转化膜,在干燥过程中残留转化液的析出相填充了晶粒间隙,提高了致密度,析出相覆盖晶粒表面使得晶粒显得细小,进一步提高了膜层的耐蚀性能,同时形成多孔结构,有助于改善钛及钛合金涂装性能。在转化膜中引入纳米硬质颗粒不改变转化膜原有的物相,其本身在转化过程中也不发生物相变化。纳米Si_3N_4颗粒多数团聚在转化膜中的磷酸锌晶粒之间的凹槽或者空隙中,有些镶嵌在晶粒侧面,有些附着在裸露基体上,推测镶嵌在晶粒侧面和附着在裸露基体上的纳米Si_3N_4颗粒有可能作为形核中心促进转化膜形核和生长。当掺杂量在0.5-2.0g/L之间时,磷酸锌生成量随着纳米Si_3N_4掺杂量增加而增多,晶粒尺寸先增大后减小,转化膜厚度有增大的趋势,在本文对比参数中当Si_3N_4掺杂量为0.5g/L时,晶粒尺寸最小,约10μm。在转化液中添加纳米Si_3N_4颗粒会改善转化膜的耐腐蚀性能,随着掺杂量增大,腐蚀电压先变大后减小,腐蚀电流先减小后增大。另外,电化学工作站检测后,在残留转化膜中可以检测到Si_3N_4,说明在内部晶粒之间甚至晶粒内部也可能含有纳米Si_3N_4颗粒。转化液中添加纳米Si_3N_4颗粒会改善转化膜与基体的结合力。
[Abstract]:Zinc phosphate conversion film is widely used in anticorrosion of metal surface, improving adhesion of coating layer and surface lubrication. At the same time, titanium has high specific strength and no magnetic properties. Many excellent properties such as good stability are playing a more and more important role in the national economy, but the titanium surface is sensitive to adhesive wear because of its easy oxidation. In this paper, zinc phosphate conversion film was prepared on the surface of titanium tetra (TA2) by using the easily realized chemical conversion method at room temperature, and the pretreatment process was discussed. Basic conversion process parameters and post-treatment process factors, and through the addition of nanometer Si_3N_4 particles. A formula for preparing nano-composite phosphate conversion film on titanium surface at room temperature was established. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were used. The phase, microstructure, mechanical properties and corrosion resistance of the conversion film were systematically characterized and analyzed by means of acoustic emission scratch tester and three-electrode electrochemical workstation. The conversion film is mainly composed of zinc phosphate tetrahydrate Zn3P04P044H20), and the technological conditions have little effect on the kinds of phase of the conversion membrane. The influence of acid pickling and surface modulation on the conversion film is irreplaceable and is the premise of preparing the complete high quality conversion film. The transformation time and temperature have little effect on the phase of the conversion film. The thickness of the conversion film prepared at 25 鈩，

本文编号：1484307