溶液前驱体等离子喷涂双稀土改性锆酸锶纳米结构热障涂层的形成机理和性能调控

Thermal barrier coating (TBC) technology is one of three most important technologies for advanced turbine engine blades. State-of-the-art 8YSZ as a standard TBC material cannot be long-term operated above 1200oC, and do not meet the demands for applications in advanced next generation turbine blades, which will be operated above 1300oC.. In this project, the nano-structured SrZrO3 TBCs co-doped with Yb2O3 and Gd2O3 will be prepared by solution precursor plasma spray (SPPS) process by using solution precursor as a feedstock. The controllable preparation of the double rare-earth oxides modified SrZrO3 solution precursor and the controlling mechanism of phase constituents and microstructures of the SPPS coatings will be studied. The internal relevant mechanism between the phase constituents, the microstructures and the thermal stability, the thermophysical properties, as well as the mechanical properties will be revealed for the SPPS double rare-earth oxides modified SrZrO3 TBCs. The nano-structured SrZrO3 TBCs co-doped with Yb2O3 and Gd2O3 will be obtained, with controllable phase constituents, micron-sized ultrafine splats, homogeneously distributed nanometer/micrometer porosity, as well as through thickness vertical cracks. AS a result, the design method and criterion of the nano-structured SrZrO3 TBCs co-doped with Yb2O3 and Gd2O3 will be established, with superior thermal stability, low thermal conductivity, and the capability to be used above 1300oC.

热障涂层技术是高性能燃气轮机叶片技术的三大技术之一。传统陶瓷热障涂层材料8YSZ 的长期使用温度不能超过1200oC，不能满足下一代高性能燃气轮机叶片在1300oC以上工作的要求。.本项目以溶液前驱体为原料，采用溶液前驱体等离子喷涂（Solution Precursor Plasma Spray, SPPS）技术制备Yb2O3-Gd2O3双稀土改性SrZrO3纳米结构热障涂层。通过研究双稀土改性SrZrO3溶液前驱体的可控制备以及SPPS涂层相组成和微观结构的调控机制，揭示SPPS 双稀土改性SrZrO3涂层相组成及微观结构与涂层热稳定性、热物理性能、力学性能的内在关联机制。获得具有组成可控、超细板条晶、均匀分布纳米/微米孔隙、贯穿涂层垂直裂纹的双稀土改性SrZrO3纳米结构热障涂层。建立1300oC 以上使用的高热稳定性、低热导率双稀土改性SrZrO3 纳米热障涂层的设计方法和准则。

传统陶瓷热障涂层材料8YSZ 的长期使用温度不能超过1200oC，不能满足下一代高性能燃气轮机叶片在1300oC以上工作的要求。本项目采用溶液等离子喷涂(SPPS)方法制备了三种双稀土改性SrZrO3涂层。采用XRD和Raman方法分析了热处理不同时间前驱体粉末的物相组成，并结合STA/QMS/FTIR联用技术分析了前驱体在高温状态下的热解、晶化以及成相过程；采用XRD、SEM、热膨胀仪以及热扩散仪等，对涂层的沉积机理、物相组成、高温相稳定性以及其它热物理性能进行了研究。主要结论如下：.（1）前驱体溶液的热分解过程分为三个阶段。第一阶段，分解产物包括ZrO2、CH3COCH3和CO2；第二阶段，主要产生SrO、Yb2O3和Gd2O3等金属氧化物；第三阶段，SrZrO3形成。.（2）三种制备态涂层中具有细小板条晶、垂直裂纹、IPB结构和微米纳米级孔隙等典型的SPPS涂层结构。Sr(Zr0.9Yb0.05Gd0.05)O2.95制备态涂层具有更细小的晶粒尺寸，并且1400 °C热处理360 h后晶粒尺寸没有明显的变化，说明双稀土元素掺杂对晶粒长大起到了明显的抑制作用。.（3）三种制备态涂层由正交SrZrO3和无定型ZrO2两相构成。1400 °C热处理5 h后，Sr(Zr0.9Yb0.05Gd0.05)O2.95涂层由正交SrZrO3和萤石结构ZrO2固溶体两相组成，Sr(Zr0.85Yb0.075Gd0.075)O2.925和Sr(Zr0.8Yb0.1Gd0.1)O2.9涂层的相组成包括正交SrZrO3和立方结构的稀土氧化物固溶体。三种涂层在热处理360 h后没发生相变，具有很好的相稳定性。.（4）三种制备态涂层都具有较低的热导率。1400 °C热处理后三种涂层的热导率均增大，但Sr(Zr0.9Yb0.05Gd0.05)O2.95涂层的增大幅度最小。三种涂层的热膨胀系数都略高于SrZrO3涂层的热膨胀系数，且Sr(Zr0.9Yb0.05Gd0.05)O2.95涂层抗烧结性最好。.（5）三种涂层的热循环寿命分别为312 cycles、253 cycles和292 cycles。Sr(Zr0.9Yb0.05Gd0.05)O2.95/8YSZ双陶瓷层涂层热循环寿命达到650 cycles，比Sr(Zr0.9Yb0.05Gd0.05)O2.95涂层提高了约一倍。