摘 要

本文系统研究了新型高温热障涂层La₂(Zr_0.7Ce_0.3)₂O₇的制备工艺及其热循环失效机理。采用高温固相反应法合成了La₂(Zr_0.7Ce_0.3)₂O₇，La₂(Zr_0.6Ce_0.4)₂O₇、La₂(Zr_0.5Ce_0.5)₂O₇三种热障涂层粉末，并由等离子喷涂制备了相应的涂层。研究结果表明，通过增加粉末中CeO₂的含量可以解决等离子喷涂过程中由于CeO₂较快挥发导致涂层中Ce含量偏低的问题。其中，由La₂(Zr_0.6Ce_0.4)₂O₇粉末喷涂制备的涂层成分更接近La₂(Zr_0.7Ce_0.3)₂O₇的化学计量比。为了克服La₂(Zr_xCe_1-x)₂O₇热膨胀系数偏低、断裂韧性不足的缺点，设计了La₂(Zr_xCe_1-x)₂O₇/YSZ双陶瓷层结构的热障涂层，并研究了La₂(Zr_0.7Ce_0.3)₂O₇/YSZ、La₂(Zr_0.6Ce_0.4)₂O₇/YSZ、La₂(Zr_0.5Ce_0.5)₂O₇/YSZ三种双陶瓷层热障涂层的热循环行为。结果表明，La₂(Zr_0.6Ce_0.4)₂O₇/YSZ双陶瓷层热障涂层的热循性能最佳，1000 ℃的热循环寿命超过190 次，明显优于La₂(Zr_0.7Ce_0.3)₂O₇/YSZ涂层(50 次）和La₂(Zr_0.5Ce_0.5)₂O₇/YSZ涂层(122次）。三种双陶瓷层热障涂层失效都发生在La₂(Zr_xCe_1-x)₂O₇涂层内部，表现出逐层剥落的特征，而YSZ/粘结层界面结合良好，表明La₂(Zr_xCe_1-x)₂O₇较低的热膨胀系数和断裂韧性仍然是La₂(Zr_xCe_1-x)₂O₇/YSZ双陶瓷层热障涂层失效的主要原因。

关键词：La₂(Zr_xCe_1-x)₂O₇ 热障涂层 双陶瓷层

Abstract

La₂(Zr₇Ce₃)₂O₇ is a promising thermal barrier coating material for the next-generation gas turbines which will operate at temperatures higher than 1200^oC. In this paper, the preparation and thermal cycling behavior of La₂(Zr_0.7Ce_0.3)₂O₇ coating were investigated. La₂(Zr_0.7Ce_0.3)₂O₇，La₂(Zr_0.6Ce_0.4)₂O₇ and La₂(Zr_0.5Ce_0.5)₂O₇ powders were synthesised by solid-state reaction at 1400^oC. Then, the corresponding coatings were prepared by atmospheric plasma spray (APS) by using La₂(Zr_0.7Ce_0.3)₂O₇，La₂(Zr_0.6Ce_0.4)₂O₇ and La₂(Zr_0.5Ce_0.5)₂O₇ powders, respectively. The results indicate that the optimized composition of La₂(Zr_0.7Ce_0.3)₂O₇ coatings could be effectively achieved by adding excess CeO₂ in the powder used for plasma spray. The coating prepared by using La₂(Zr_0.6Ce_0.4)₂O₇ powder had a composition close to the stoichiometric ratio of La₂(Zr_0.7Ce_0.3)₂O₇. Since single La₂(Zr_xCe_1-x)₂O₇ coating usually has a poor thermal shock resistance due to its relatively lower thermal expansion coefficient and fracture toughness, double-ceramic-layer thermal barrier coatings based on La₂(Zr_xCe_1-x)₂O₇/YSZ were designed in this study. La₂(Zr_0.6Ce_0.4)₂O₇/YSZ double-ceramic-layer thermal barrier coating had a lifetime more than 190 cycles in the thermal cycling test at 1000 ^oC, which was much longer than that of La₂(Zr_0.7Ce_0.3)₂O₇/YSZ coating (50 cycles) and La₂(Zr_0.5Ce_0.5)₂O₇/YSZ coating (122 cycles). The spallation of these three kinds of double-ceramic-layer coatings all occur in the inner of the La₂(Zr_xCe_1-x)₂O₇ coating while the YSZ/ bond coat interface kept intact, indicating that the main failure mechanism can still be attributed to the low thermal expansion coefficient and fracture toughness.

Key Words：La₂(Zr_xCe_1-x)₂O₇ Thermal barrier coating Double ceramic layer

目录

第1章 绪论 1

1.1引言 1

1.2热障涂层的发展现状 2

1.3热障涂层结构 3

1.3.1经典结构 3

1.3.2梯度结构 4

1.3.3复合结构 4

1.3.4厚涂层结构 5

1.3.5双层结构 5

1.4热障涂层的制备技术 5

1.4.1等离子喷涂 6

1.4.2电子束-物理气相沉积 7

1.5热障涂层陶瓷层材料 7

1.5.1经典热障涂层材料-YSZ 7

1.5.2其他热障涂层材料 8

1.5.3新型热障涂层材料 9

1.6本文的主要研究内容及意义 9

第2章La₂(Zr_xCe_1-x)₂O₇粉末的制备、加工与测试 11

2.1实验原料 11

2.1.1实验合成原料 11

2.1.2基体材料 11

2.1.3喷涂材料 11

2.2相关设备 11

2.3研究过程 12

2.3.1La₂(Zr_xCe_1-x)₂O₇粉末的制备 12

2.3.2La₂(Zr_xCe_1-x)₂O₇粉末的喷雾造粒 15

2.3.3La₂(Zr_xCe_1-x)₂O₇粉末的成型加工 16

第三章La₂(Zr_xCe_1-x)₂O₇热障涂层的制备、表征与热循环 17

3.1 La₂(Zr_xCe_1-x)₂O₇热障涂层的制备 17

3.1.1制备工艺 17