基于溶胶凝胶法的YAlO3/Ti2AlN(C)复合涂层的制备与性能研究

IMR OpenIR

	基于溶胶凝胶法的YAlO3/Ti2AlN(C)复合涂层的制备与性能研究
	范超
学位类型	硕士
导师	杨锐
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料工程
关键词	开裂氧化烧结 Yalo3/ti2aln(c)复合涂层溶胶凝胶法 Cracking Oxidation Sintering Yalo3/ti2aln Composite Coatings Sol-gel Method
摘要	" 针对γ-TiAl基金属间化合物在800℃以上抗氧化性能的严重不足，本文以溶胶凝胶法为基础在γ-TiAl基体表面对YAlO3/Ti2AlC、YAlO3/Ti2AlN两种复合涂层的制备及性能进行了探索性的研究。文章中运用高温金相显微镜（HTOM）、热重-差热分析（TG-DTA）、高温X射线衍射（HTXRD）、场发射扫描电镜（FESEM）、X射线光电子能谱分析（XPS）等原位以及非原位观察分析手段，研究了涂层在100~400℃进行干燥和低温灼烧时的开裂行为、涂层的烧结工艺和机制以及涂层的高温氧化行为。为合理地对涂层的开裂行为进行解释，建立了涂层中应力在干燥与低温灼烧过程的演变模型。根据该模型，纳米粉-凝胶体系中H2O、有机物等物质的蒸发是涂层中应力产生的根源，应力的演变在100~400℃的升温过程中可被划分三个阶段，其中涂层的开裂发生在第三阶段。研究表明，升温速率、TiAl3颗粒、提拉速度等通过影响应力在涂层中的分布而间接地影响涂层的开裂情况，5℃/min的升温速率和12mm/min的提拉速度是涂层制备时比较理想的选择。烧结产物取决于气氛、气压和温度等工艺参数，在1000℃ 、0.02MPa的氩气气氛保护下制备了YAlO3/Ti2AlN复合涂层，在1260℃ 、160MPa的氩气环境中制备了YAlO3/Ti2AlC复合涂层。用粉末系统烧结理论解释了涂层的烧结行为，干燥和低温灼烧方式影响粉末颗粒的接触，而高温烧结工艺影响物质的迁移和扩散，进而影响烧结颈的长大。Al通过晶内扩散、晶界扩散、表面扩散和蒸发凝聚等扩散和迁移机制影响最终烧结产物。 900℃下的等温氧化和循环氧化实验表明，YAlO3/Ti2AlC、YAlO3/Ti2AlN两种复合涂层的氧化增重曲线都符合抛物线规律，且整个实验过程中涂层形貌保持完好；而1000℃下两种涂层则均出现了较为严重的剥落。氧化产物主要为Al2O3和TiO2，氧化层由3~4个Al2O3、TiO2含量各不相同的亚层构成。900℃下两种涂层各氧化亚层Al2O3和TiO2含量相近；而1000℃下两种涂层的最外氧化层均富TiO2，且YAlO3/Ti2AlN涂层的内氧化层同样富TiO2。
其他摘要	"Due to the seriously insufficient oxidation resistance of γ-TiAl based intermetallic compounds at temperatures above 800℃, the exploratory study on preparation and properties of two kinds of composite coatings, i.e. YAlO3/Ti2AlC and YAlO3/Ti2AlN coatings deposited on γ-TiAl substrate using a sol-gel method, was conducted in this article. A variety of in situ and ex situ observing and analyzing techniques such as high-temperature optical microscopy (HTOM), thermogravimetry-differential thermal analysis (TG-DTA), high-temperature X-ray diffraction (HTXRD), field-emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) were applied, so as to investigate the cracking behavior of coatings during drying and pyrolysis, the sintering process and its mechanism, and also the oxidation behavior of these two kinds of coatings at high temperatures. In order to rationally explain the cracking behavior of coatings, a model of stress development during drying and pyrolysis was established. According to this model, evaporation of H2O and organic species in the nanoparticles-gel system was the reason of stress in coatings. Upon heating from 100℃ to 400℃, stress in such coatings developed dynamically, and evolution of which could be divided into three stages. As what observed, cracking of coatings began in the third stage. By affecting the distribution of strees in coatings, factors like TiAl3 particles, heating rates and withdrawal speeds all had indirect influences on cracking. A heating rate of 5℃/min and withdrawal speed of 12mm/min were preferred when preparing coatings. Phase composition of coatings had a strong dependence on parameters like temperature, sintering atmosphere and its pressure. YAlO3/Ti2AlN composite coatings were prepared in Ar atmosphere at 1000?C and 0.02MPa, while YAlO3/Ti2AlC coatings were deposited in the same atmosphere at 1260℃ and 160MPa. Sintering behavior of coatings was explained with the aid of sintering theory of powder system. The manner in which coatings were processed during drying and pyrolysis determined contacts between particles; and the way of sintering had the same effect on transport of matter in coatings, which could eventually affect the growth of the sintering neck. Al could diffuse or migrate in several ways, e.g. intracrystalline diffusion, boundary diffusion, surface diffusion and evaporation condensation, which shaped the products. Based on the isothermal and cyclic oxidation experiments, the mass gain of both YAlO3/Ti2AlC and YAlO3/Ti2AlN composite coatings showed a parabolic increase at 900℃, and no cracking was observed; however, at 1000℃, both coatings cracked severerly. The oxide scales were composed of a mixture of Al2O3 and TiO2, forming about 3~4 layers. At 900℃, TiO2 could be found in all layers, with similar amount of Al2O3, but at 1000℃ TiO2 dominated the outermost layer of both coatings, meanwhile the inner layer of YAlO3/Ti2AlN coatings.
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64543
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	范超. 基于溶胶凝胶法的YAlO3/Ti2AlN(C)复合涂层的制备与性能研究[D]. 北京. 中国科学院金属研究所,2012.