双稀土改性SrZrO3涂层中第二相对涂层物理性能及寿命的影响机制

8YSZ as a standard TBCs material can not be long-term operated above 1200oC, thus can not meet the requirements of the next generation high-performance gas turbines.The double rare-earth oxides co-doped SrZrO3 (rare-earth co-doped SrZrO3) ceramic designed by "defect cluster" method reveals better high-temperature phase stability and lower thermal conductivity than SrZrO3. The composition of the air plasma sprayed rare-earth co-doped SrZrO3 coating deviated from that of the feedstock, resulting in development of the secondary phase t'/c-ZrO2 inevitably.Therfore, it is necessary to investigate the content of the secondary pahse t'/c-ZrO2 in rare-earth co-doped SrZrO3 coating and the different heat treatment conditions on the influencing rules of phase transition mechnism, thermophysical and mechanical properties of the coating, revealing the relationship between composition, microstructure and properties of the coating. The coating structure of double ceramic layered TBC (DCL-TBC) for optimized rare-earth co-doped SrZrO3 and 8YSZ will be designed and prepared. The failure mechanisms and the main factors affecting the TBCs lifetime of the SrZrO3/8YSZ coating system will be concluded through thermal cycling tests at temperatures above 1300oC with temperature gradient. As a result, the design methods and criteria for the rare-earth co-doped SrZrO3 coating system, which has low thermal conductivity, long lifetime and can be operated above 1300oC, will be established.

传统陶瓷热障涂层材料8YSZ的长期使用温度不能超过1200oC，已不能满足下一代高性能燃气轮机的设计和使用要求。采用"缺陷簇"法设计的双稀土氧化物掺杂改性SrZrO3（稀土SrZrO3）陶瓷具有高温相稳定性好和低热导率特点。鉴于大气等离子喷涂的涂层成分偏离原始粉末成份，使得稀土SrZrO3涂层中不可避免出现第二相t'/c-ZrO2并影响涂层的性能。因此有必要对稀土SrZrO3涂层中第二相t'/c-ZrO2含量及不同热处理条件对涂层的相变机制、热物理性能、力学性能的影响规律进行系统地研究，揭示稀土SrZrO3涂层中成分、组织与性能的内在规律。并对优选出的稀土SrZrO3/8YSZ进行双陶瓷层结构涂层体系设计，在1300oC以上且具有温度梯度的条件下研究其热循环寿命，确定其失效模式及影响热循环寿命的关键物理参数，建立1300oC以上使用的低热导率、长寿命稀土SrZrO3涂层体系的设计方法和准则

传统陶瓷热障涂层材料8YSZ的长期使用温度不能超过1200oC，已不能满足下一代高性能燃气轮机的设计和使用要求。本项目制备了SrZrO3、Sr(Zr0.9Yb0.05Gd0.05)O2.95、Sr(Zr0.9Yb0.05Y0.05)O2.95和Sr1.1(Zr0.9Yb0.05Gd0.05)O3.05四种涂层，分别在1400oC、1500oC和1600oC进行长时间热处理。研究结果表明，SrZrO3制备态涂层中的t-ZrO2在1600oC热处理10 h后全部转变为m-ZrO2，Sr(Zr0.9Yb0.05Gd0.05)O2.95和Sr(Zr0.9Yb0.05Y0.05)O2.95涂层中的t-ZrO2含量随着热处理时间的增加而增加，但始终保持t-ZrO2，而Sr1.1(Zr0.9Yb0.05Gd0.05)O3.05涂层即使在1600oC热处理360 h后没有发现第二相。Yb2O3和Gd2O3共掺杂不仅能有效地抑制SrZrO3的相变，而且可以有效地抑制双稀土改性SrZrO3涂层中t-ZrO2的相变。.制备态SrZrO3涂层的热导率在1000℃下为1.32 W•m-1•K-1，掺杂稀土元素的SrZrO3涂层热导率比单相SrZrO3涂层明显降低，其中降低最明显的是Sr(Zr0.9Yb0.05Gd0.05)O2.95，在1000℃下其热导率为0.79 W•m-1•K-1。双稀土改性SrZrO3涂层1600℃热处理360h后Sr(Zr0.9Yb0.05Gd0.05)O2.95涂层的热导率最低（2.39 W•m-1•K-1@1000oC），而Sr(Zr0.9Yb0.05Y0.05)O2.95（2.81 W•m-1•K-1@1000oC）和 Sr1.1(Zr0.9Yb0.05Gd0.05)O3.05（2.83 W•m-1•K-1@1000oC）涂层的热导率较高，说明Yb+Gd双稀土改性对于降低SrZrO3涂层的热导率更有效。.SrZrO3、Sr(Zr0.9Yb0.05Gd0.05)O2.95、Sr(Zr0.9Yb0.05Y0.05)O2.95和Sr1.1(Zr0.9Yb0.05Gd0.05)O3.05四种单陶瓷层涂层体系的热循环寿命较短，优选出的Sr(Zr0.9Yb0.05Gd0.05)O2.95/8YSZ双陶瓷层涂层在1350oC燃烧台架热循环条件下其热循环寿命超过5000次。