【作者】 常华；

【导师】 骆心怡；

【作者基本信息】 南京航空航天大学 ， 材料学， 2007， 硕士

【摘要】 本文首先简述了功能梯度涂层、阻氚渗透涂层、双层辉光渗金属技术、热浸镀铝技术的概念、原理及发展现状。综述了近十年来阻氚渗透涂层的研究进展,重点对不锈钢表面四种常见阻氚渗透涂层(氧化物涂层、铝化物涂层、钛基陶瓷涂层、硅化物涂层)的制备方法、阻氚机理及其各自的优缺点进行了讨论和对比。在总结目前阻氚涂层研究和应用现状的基础上,提出了利用双层辉光渗金属技术和热浸镀技术在316L不锈钢表面进行渗铝、渗氧并原位反应制备铝基阻氚渗透涂层的新思路。利用双层辉光渗金属技术在316L不锈钢表面制备了渗铝涂层。通过摸索试验确定了源极的类型和源极电压、工件电压、温度等工艺参数,然后分别以工作气压和极间距为考察对象,以涂层厚度、表面铝元素含量以及表面质量为指标,对工艺参数进行了优化,利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)和辉光放电光谱仪(GDS)等对涂层的组织、成份和相的分布进行了研究,确定了合适的工艺参数为工件电压450V,源极电压950V,极间距30mm,工作气压75Pa,温度980℃,脉冲电源占空比0.3,所得渗铝层表面质量良好,涂层平均厚度20μm,铝、铁呈良好梯度分布。通过热浸镀铝和随后高温扩散的方法在316L不锈钢表面制备了铁铝梯度涂层。通过对涂层厚度、组织、合金元素分布、相组成和显微硬度进行分析,确定了合适的工艺为750℃下浸镀10分钟,并950℃时扩散4小时。制备的涂层表面质量较好,无明显漏镀现象。涂层与基体结合紧密,热处理后孔洞基本消除,厚度平均122μm,铝、铁呈良好梯度分布。利用工业用氮气中残留的氧气成功地在316L不锈钢渗铝涂层表面渗入氧元素,渗氧温度900℃,4小时,渗氧层厚度达15μm,X射线光电子能谱(XPS)分析表明渗入的氧与先行渗入的铝进行了择优氧化,原位反应生成了氧化铝,并且除表面是一层致密的氧化铝膜外,在氧化铝膜以内氧化铝呈现梯度分布。通过对比试验发现,双层辉光渗金属技术制备的涂层抗热震性和热氧化性均强于热浸镀制备的涂层,其中抗热震性是其2倍以上。更多还原

【Abstract】 In the first part of this dissertation, conception, principle and history of functional gradient coatings, tritium permeation barriers, double glow plasma surface alloying and hot dipping were overviewed. The advantages and shortcomings of the typical tritium permeation barriers coating, such as oxides, aluminum-based coatings, titanium-based coatings and silicide coatings on stainless steel surface, were discussed in detail respectively. On the basis of these, double glow plasma surface alloying and hot dipping, as new methods used to alumetize and oxidize, were put forward to prepare tritium permeation barriers.Alumetized coating have been prepared by double glow plasma surface alloying. Firstly, the processing parameters such as type of source polar, work temperature, voltage of source polar and voltage of workpiece polar were determined according to groping experimentation. Secondly, the other processing parameters such as work air pressure and distance between workpiece polar and source polar were optimized according to thickness of coating, aluminium content of surface and quality of surface. Microstructure, composition and phase were studied by scanning electron microcopy(SEM), energy dispersion X-ray spectrum(EDS), X-ray diffraction(XRD) and glow discharge spectrometry(GDS). The optimal processing parameters are as follows: workpiece polar voltage is 450V, source polar voltage is 950V, distance between the two polar is 30mm, work air pressure is 75Pa, work temperature is 980℃, duty ratio of impulsing power source 0.3. On this condition, the average thickness coating with good quality is 20μm while the composition of the alumetized coating from surface to interior is gradient distribution.In the other hand, alumetized coating have been prepared by hot dipping and subsequent high temperature diffusion. The optimal processing parameters are dipping temperature 750℃, time10 minutes, diffusion temperature 950℃and time 4 hours.The average thickness of coating is 122μm. The coating is compact, gradient distribution, uniform and has good adherence with the substrate.As-prepared Alumetized coating was oxygenated by rudimental O2 in 98.5%N2 as source. Oxygenated at 900℃for 4 hours, thickness of oxide is 15μm. The result of X-ray photoelectron spectroscopy (XPS) shows that oxygen has preferred to combine with aluminium. But alumina is in gradient distributions in the oxide film except surface.Comparing with the hot-dip coating, the one fabricated by double glow plasma surface alloying has more excellent properties of thermal shock resistance and oxidation resistance.更多还原