大气等离子喷涂热障涂层显微结构与热导率关系的定量研究

发布时间：2018-05-14 23:38

本文选题：EBSD图像 + 显微结构　；参考：《上海应用技术大学》2017年硕士论文

【摘要】：Y_2O_3部分稳定的ZrO_2具有较低的热导率和热膨胀系数、韧性好、强度高以及良好的耐腐蚀、抗热冲击性能,加之价格便宜等优势,而成为目前使用最广泛的热障涂层材料。然而,针对未来热障涂层材料需要满足更低热导率的要求,热障涂层的研究面临着诸多的挑战。需要分析影响涂层热导率的因素。YSZ涂层的显微结构是由相组成,裂纹,气孔,片层之间的界面,以及晶界等组成。这些都是影响涂层的热导率的重要的因素。但是又由于涂层中界面的存在,直接通过涂层的显微结构分析各个因素对热导率的影响是很困难的。为了解决这个问题,实验中先研究YSZ陶瓷,通过压制烧结的方法,制备基本致密的氧化锆陶瓷,制备的氧化锆陶瓷不是层状结构,所以没有片层之间的界面。然后,基于YSZ陶瓷的EBSD图像,通过有限元模拟的方法,计算分析了四方相以及晶界的热导率。这个是本文研究的一部分内容。另外,在这个实验的基础上,考虑界面的理想状态下的分布情况,基于涂层的EBSD图像,利用有限元模拟的技术手段,模拟得出的结果,与实验测得的涂层的热导率数值进行对比,两者之间的误差在10%以内。通过有限元网络模型,计算了单斜相,裂纹气孔,晶界,界面以及界面与裂纹气孔之间的相互作用对涂层的热导率的影响系数。主要结果有:(1)通过压制烧结的方法,制备出了基本致密的YSZ陶瓷,通过改变保温温度,获得了晶粒大小不同的YSZ陶瓷。基于两种YSZ陶瓷的EBSD图像,计算中了 YSZ陶瓷中四方相以及晶界的热导率的数值。(2)通过大气等离子喷涂技术,通过不同的喷涂参数,制备出了三种不同显微结构的YSZ热障涂层,基于涂层的EBSD图像结合界面的理想状态下的部分情况,获得了涂层的理想的显微结构模型,通过这个模型计算的涂层的热导率与实验测得的热导率的数值之间的误差在10%以内。(3)基于涂层的理想状态下的模型,通过有限元模拟计算,通过对比涂层中有无界面,计算出了界面对涂层的热导率的影响系数。通过对比基体中有无裂纹气孔,同时加入界面的影响,两者之间热导率的差值,得出了裂纹气孔与界面之间相互作用对涂层热导率的影响系数。(4)基于涂层的EBSD图像,通过有限元模拟的方法,通过对比涂层中有无裂纹气孔两者热导率之间的差值,可以计算得出了裂纹气孔对热导率的影响系数,通过对比有无单斜相的两个涂层之间的热导率的差值,可以计算出单斜相对热导率的影响系数。通过对比有无晶界的两个涂层之间的热导率的差值,可以计算出晶界对热导率的影响系数。
[Abstract]:Y_2O_3 partially stabilized ZrO_2 has the advantages of low thermal conductivity, thermal expansion coefficient, good toughness, high strength, good corrosion resistance, thermal shock resistance and low price, so it has become the most widely used thermal barrier coating material. However, the research of thermal barrier coatings is faced with many challenges in order to meet the requirements of lower thermal conductivity in future thermal barrier coating materials. The microstructure of YSZ coating is composed of phase, crack, porosity, interface between lamellar layers and grain boundary. These are important factors affecting the thermal conductivity of the coating. However, due to the existence of interface in the coating, it is difficult to analyze the influence of various factors on the thermal conductivity directly through the microstructure of the coating. In order to solve this problem, the YSZ ceramics were studied in the experiment. The basic dense zirconia ceramics were prepared by pressing and sintering. The zirconia ceramics were not layered structure, so there was no interlamellar interface. Then, based on the EBSD images of YSZ ceramics, the thermal conductivity of tetragonal phase and grain boundary is calculated and analyzed by finite element simulation. This is a part of this study. In addition, on the basis of this experiment, considering the distribution of the interface in ideal state, the EBSD image based on the coating is simulated by the technical means of finite element simulation. Compared with the experimental results, the error between them is less than 10%. The influence coefficients of monoclinic phase, crack porosity, grain boundary, interface and interaction between interface and crack pore on thermal conductivity of coating were calculated by finite element network model. The main results are as follows: (1) the compact YSZ ceramics were prepared by pressing sintering, and the YSZ ceramics with different grain sizes were obtained by changing the holding temperature. Based on the EBSD images of two kinds of YSZ ceramics, the thermal conductivity of tetragonal phase and grain boundary in YSZ ceramics was calculated. Three kinds of YSZ thermal barrier coatings with different microstructure were prepared by atmospheric plasma spraying technology and different spraying parameters. Based on the EBSD image of the coating, the ideal microstructure model of the coating is obtained by combining the part of the interface in the ideal state. The error between the thermal conductivity of the coating calculated by this model and the experimental value of the thermal conductivity is less than 10%.) based on the ideal state of the coating, the finite element method is used to calculate the thermal conductivity of the coating and the interface between the coating and the coating is compared. The influence of the interface on the thermal conductivity of the coating was calculated. By comparing the existence of crack pores in the matrix and the influence of interface, the difference of thermal conductivity between them is obtained. The influence coefficient of the interaction between crack porosity and interface on the thermal conductivity of the coating is obtained. The EBSD image based on the coating is obtained. By means of finite element simulation and by comparing the difference between the thermal conductivity of the coating with or without crack porosity, the influence coefficient of crack porosity on thermal conductivity can be calculated. By comparing the difference of thermal conductivity between two coatings with or without monoclinic phase, the influence coefficient of monoclinic relative thermal conductivity can be calculated. By comparing the difference of thermal conductivity between two coatings with or without grain boundary, the influence coefficient of grain boundary on thermal conductivity can be calculated.
【学位授予单位】：上海应用技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.1

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