IMECH-IR  > 力学所知识产出(1956-2008)
改善等离子涂层界面结合性能及抗氧化性能的研究:激光熔覆改善等离子涂层界面结合性能的研究及热障涂层(TBCs)中热氧化生长(TGO)导致涂层失效的机理及控制
马岳
Thesis Advisor段祝平
2000
Degree Grantor中国科学院力学研究所
Place of Conferral北京
Subtype博士后
Keyword等离子喷涂 激光熔覆 界面结合性能 热障涂层 离子注入 涂层失效 热氧化生长
Abstract本文针对当前等离子涂层(热障涂层)中存在的关键问题进行了研究。第一篇以氧化锆热障涂层为研究对象,在基体待喷表面进行激光熔覆预处理,在涂层-基体的界面处形成熔覆层。借助于扫描电子显微镜,X射线能谱分析仪,显微硬度仪及X射线衍射仪分析、测定了熔覆层的组织及性能,其结果表明:熔覆层中的成分及显微硬度沿厚度方向,均呈梯度分布,起到了涂层到基体的成分、组织及显微硬度的逐渐过渡的作用,达到了消除涂层-基体的异相界面,改善界面结合状况的目的。本篇中还进行涂层的砂轮切割试验,拉伸试验及三点弯曲试验,以研究涂层的抗振动、脱落性和界面结合强度等性能。通过与普通涂层比较:基体表面经激光熔覆预处理,形成熔覆层,能够明显提高涂层的抗振动脱落性,提高界面结合强度及界面抗拉、抗剪能力。并应用ANSYS有限元程序,分析了涂层系统中的热引起的残余应力的分布,结合试验结果得出“熔覆层明显提高界面承载能力”的结论。第二篇重点研究近年来热障涂层(TBC_s)中存在的热氧化生长(TGO),导致涂层失效的热点问题。以冶金学原理为理论,试验结果为依据,分析了涂层服役的环境、结合层的结构及元素间的相互作用对TGO的影响,分析结果说明:长期高温氧化环境,NiCrAl层表面氧化膜中的晶格缺陷和第三元素Zr的相互作用,促进TGO的形成及生长。采用ANSYS有限元程序计算了涂层系统的残余应力分布,计算结果表明:TBC_s中TGO的形成及厚度增加,改变了涂层系统的残余应力分布,增加了涂层系统的最大残余应力值,是导致涂层失效不容忽视的一个因素。综合以上试验、理论分析及计算的结果,创新性地提出了采用离子注入的方法,控制TGO,改善TBC_s的性能。本篇用特殊设计的氧化试验,证实了离子注入工艺的确能够改善TBC_s的抗氧化性能。并通过深入分析离子注入的工艺及注入元素的种类对TBC_s性能的影响,提出了:①NiCrAl层表面注入Cr,明显改善TBC_s的抗氧化性。②注入Zr后,促进TGO的迅速生长,在NiCrAl层中形成许多立体交叉的TGO网,严重恶化性能,降低TBC_s的抗氧化性。同时,还进一步分析了TBC_s的失效机理,提出了TGO是导致TBC_s失效的主要因素。本文的研究结果是对TBC_s传统失效理论的一个补充和扩展,本课题的研究力求解决TBC_s存在的问题,为其应用开辟广阔的前景。
Other AbstractThe present study is focused on the key problems of the interface between coating and substrate in plasma spraying. Firstly, (ZrO_2) thermal barrier coatings(TBC_s) act as a sample to research. The surface of substrate is pretreated by laser cladding to form a cladding layer of 10 μm at the interface of coating-substrate, of which the microstructures and properties are investigated by means of SEM, XRD and Micro-hardness Meter. The research reveals that there is a gradient distribution in composition and micro-hardness in the thickness direction of cladding layer, which has played a bridge role between coating and substrate, and has smoothed out the interface. In order to study the properties of coating resistance against spalling as well as coherence with substrate, the grinding wheel cut test, tensile test and three-point bend test are carried out. Comparing with conventional coating, the resistance to spalling of coating can be obviously improved and the coherent strength, tensile strength as well as shear strength at interface can be much increased by using laser cladding technology. Analysis on the distribution of residual stresses due to thermal mismatch within coating systems has been conducted by ANSYS FEM code, and the results have shown that the capability of withstanding the load acting on the interface between substrate and coating with cladding layer is markedly increased. Secondary, recently, a hotspot problem on coating failure due to thermal growth oxidation (TGO) existing in thermal barrier coating is studied. The analysis which aims at improving the condition of coating service, the structure of bond layer and the interaction of elements are conducted according to the theory of metallurgy and experiments results. The test has shown that the service under the condition of high temperature and oxidation, crystal flaw within oxidation layer at surface of NiCrAl coating and the effect of Zr on oxidation layer will promote to form and speed up TGO. It has been shown that the formation of TGO and increase of its thickness will change the distribution of residual stress and increase the maximum residual stress of coating system through calculating the distribution of residual stresses by using ANSYS FEM code, which explains that TGO is a key element to result in coating failure. A technology of injecting ion into the surface of NiCrAl coating is used to control the TGO and to improve the properties of coating by summing up the results of experiments and analyzing mechanism. Resistance against oxidation of TBC_s can be improved by injecting ion technology, which has been confirmed by using a special design oxidation test. Through analyzing on the technology of injecting ion and the effect of elements on properties of TBC_s, it points out: ①Injecting Cr into the surface of NiCrAl layer can markedly improve the resistance against oxidation in coating systems. ② Injecting Zr into it will promote to form a lot of three-dimensional across net of TGO and worsen the properties of resistance against oxidation in coating system. A conclusion that TGO is a key of leading to the coating failure has been obtained by analyzing the failure mechanism of TBC_s. The research is a supplement and extension for tradition failure theory of TBC_s. The goal of investigation is to solve the problems existing in TBC_s and to expand the application field of TBC_s.
Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/47264
Collection力学所知识产出(1956-2008)
Recommended Citation
GB/T 7714
马岳. 改善等离子涂层界面结合性能及抗氧化性能的研究:激光熔覆改善等离子涂层界面结合性能的研究及热障涂层(TBCs)中热氧化生长(TGO)导致涂层失效的机理及控制[D]. 北京. 中国科学院力学研究所,2000.
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