大气等离子喷涂热障涂层CMAS防护层成分及厚度优化

Composition and Thickness Optimization of Anti-CMAS Layer on Air Plasma Sprayed Thermal Barrier Coatings

目的优化热障涂层(TBCs)CMAS(CaO-MgO-Al_2O_3-SiO_2)阻抗层的成分和厚度,使其能有效阻抗CMAS沉积物的腐蚀,并同时与热障涂层有较高的结合力。方法首先利用多孔无压烧结陶瓷块体研究了不同含量Al_2O_3和8YSZ(8wt.%氧化钇稳定氧化锆)均匀混合后在高温(1250℃)条件下对CMAS沉积物的防护作用。采用扫描电子显微镜(SEM)、能谱仪(EDS)以及X射线衍射(XRD)仪,分析研究了CMAS腐蚀层的显微结构、腐蚀深度及反应产物。其次,基于最优成分,利用大气等离子喷涂(APS)制备了具有8YSZ/Al_2O_3陶瓷层的热障涂层。对CMAS腐蚀厚度进行分析测量,提出CMAS阻抗层的厚度。结果 Al_2O_3的添加可以有效地阻碍CMAS的渗入,并且Al_2O_3含量越多,防护效果越好。但是CMAS的渗入深度和氧化铝的添加量呈非线性关系。结合TBC陶瓷层的热学性能和力学性能的要求,本实验中最佳的TBCs复合陶瓷层组分为70wt%8YSZ+30wt%Al_2O_3。基于实验结果,提出YSZ/Al_2O_3复合陶瓷层(50μm)-YSZ陶瓷层(150μm)的双层TBC陶瓷层结构,并综合计算出复合陶瓷层的热膨胀系数为9.93×10-6℃-1以及双层TBC陶瓷层的热导率为2.4 W/(m·K)。最后对Al_2O_3减缓CMAS腐蚀的机理进行了量化分析。结论 YSZ/Al_2O_3复合阻抗层的最优成分为70wt%8YSZ+30wt%Al_2O_3,厚度为50μm,能有效阻碍高温下CMAS腐蚀。

The work aims to investigate composition and thickness of impedance layers on thermal barrier coatings（TBCs）, so that the layers can effective impede corrosion of CMAS deposit and also easily adhere to thermal barrier coatings. Protection effects of uniformly blended different content of nano-sized Al2O3 and 8 YSZ on CMAS deposit were studied with porous pressureless sintered ceramic pellets at high temperature. Microstructure, corrosion depth and reaction product of the CMAS corro-sion layers was analyzed and studied with scanning electron microscope, energy dispersive spectrometer and X-ray diffractometer, respectively. Then thermal barrier coatings with 8 YSZ/Al2O3 ceramic layers were prepared by performing air plasma spraying（APS） based on optimal composition. Corrosion depth of CMAS was analyzed and measured, and thickness of CMAS impedance layers was proposed. Addition of Al2O3 can effectively prevent CMAS from infiltrating. Moreover, the higher the Al2O3 content was, the better the protection effects were. However, there was a nonlinear correlation between CMAS infiltration depth and Al2O3 addition. Concerning thermal properties and mechanical properties of the TBC ceramic layers, optimal composition of TBC composite ceramic layers was determined to be 70 wt%8 YSZ＋30 wt%Al2O3. Based upon the experimental results, bilayer TBC ceramic layer structure consisting of YSZ/Al2O3 composite ceramic layers（50 μm） and YSZ ceramic layers was proposed. According to overall calculations, thermal expansion coefficient of the YSZ/Al2O3 composite ceramic layers was 9.93×10-6 ℃-1, and thermal conductivity of the bilayer TBC ceramic layers was 2.4 W/（m·K）. Finally, the mechanism of CMAS corrosion being mitigated by Al2O3 was quantitatively analyzed. The optimal composition of YSZ/Al2O3 composite ceramic layers is 70 wt%8 YSZ＋30 wt%Al2O3, and thickness is 50 μm, which can effectively prevent CMAS corrosion at high temperature.