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热障涂层是一种沉积在高温合金基底表面，保护基底材料免受高温侵蚀的陶瓷材料。因其良好的耐高温性、较低的热导率、与基底匹配的热膨胀性能而被广泛应用在航空发动机燃烧室等高温部件表面，成为现代航空设备（燃烧室、进气道、尾喷管等）不可取代的隔热材料。目前实际广泛使用的热障涂层是氧化钇部分稳定氧化锆(YSZ)，而YSZ陶瓷材料长时间使用温度不能超过1200 °C。在航空、航天领域，随着高超音速飞行器的出现及发展，其高温部件表面温度已经远远超过1200 °C，需求接近2300 °C，涂层表面温度达到1600 °C以上，现有的热障涂层已经不能满足武器型号的超高温需求，必须研制超高温条件下使用的新型低导热系数热障涂层。因此，具有低导热系数、高热膨胀系数、高温相稳定性、低烧结率和耐高温腐蚀性能的新型陶瓷涂层成为研究的重点和热点。本文针对航空事业发展的迫切需求，以综合性能较好的氧化锆为主体材料，通过掺杂稀土元素和非稀土元素构造多元固溶体体系，设计合成新型低导热超高温热障涂层材料M0.02Gd0.025Yb0.025Y0.05Zr0.88O1.94(M= Dy、Er、Eu、Sm、Nd)和N0.02Dy0.02Gd0.025Yb0.025Y0.05Zr0.86Ox(N= Ti、Mn、Si、Mg、Cr)。系统研究了热障涂层粉体、涂层的晶型结构和涂层热力学性能，并分析了离子半径和化合价对涂层性能的影响；同时借助现代计算机模拟技术，模拟涂层在烧蚀过程中温度场变化、热应力变化和形变，预测了涂层最容易失效的位置；为进一步提高涂层性能，对涂层孔隙结构进行了设计，改善涂层热应力集中问题，延长热障涂层使用寿命，提高了涂层的隔热性能，降低了到达高温合金基底的温度。具体研究内容和结果如下：（1） 二元离子掺杂(La1-xScx)2Zr2O7粉体和涂层制备及其性能研究对热导率较低的La2Zr2O7涂层进行掺杂改性，采用半径较小的近稀土Sc3+离子进行掺杂，研究了不同含量Sc3+离子掺杂对涂层热力学性能的影响，结果表明，钪离子掺杂能降低锆酸镧涂层的热导率。当Sc3+掺杂量为0.1时，其热导率最低，其中掺杂Sc0.1在1600 °C时，涂层热导率比单一La2Zr2O7涂层的热导率降低8.8%。（2） 四元M0.02Gd0.025Yb0.025Y0.05Zr0.88O1.94陶瓷粉体和涂层制备及其性能研究采用高温固相法制备的新型四元M0.02Gd0.025Yb0.025Y0.05Zr0.88O1.94陶瓷粉体物相单一、晶体结构良好。而且粉体制备工艺简单、产量高、性能稳定，适合规模化批量生产。利用大气等离子喷涂工艺，在高温合金(GH4169）基底的表面先制备厚度约为100 μm厚的NiCoCrAlY金属粘结层，最后在粘结层表面制备陶瓷面层。与YSZ涂层进行对比，新型超高温热障涂层的高温抗烧蚀性能更好，热导率更低，可作为未来航空发动机的超高温热障涂层。（3） 五元N0.02Dy0.02Gd0.025Yb0.025Y0.05Zr0.86Ox掺杂改性陶瓷粉体和涂层制备及其性能研究针对上述四元稀土氧化锆基热障涂层抗热震性能欠佳的情况，我们利用熔点较低的非稀土氧化物对其进行了进一步的掺杂改性。同时，元素半径差异大能改变平均自由程，增大散射面，增加声子散射，最终降低热导率。通过固相法制备的改性五元陶瓷涂层在保持了四元涂层的优点外，提高了涂层的抗热震性能，同时降低涂层的热导率，特别是在1600 °C，其热导率为0.974 W/(m?K)，比传统YSZ（1.749 W/(m?K)）涂层热导率降低了44.3%。因此，改性后的新型热障涂层是航空发动机隔热材料的理想选择。（4） 热障涂层孔隙结构设计及其热力学性能研究一方面通过掺杂改性的化学手段对涂层性能进行改进，另一方面在现有涂层的基础上对涂层的物理孔隙结构进行设计。理论计算能以最低的成本和最快的速度优化涂层孔结构，对未来涂层结构的设计优化起到理论指导作用。通过计算发现带有半圆形孔隙结构的涂层具有最小的应变、最佳的隔热性能和最小的热应力。这是首次通过对涂层进行物理孔结构的改进来提升涂层性能的尝试及报道。;Thermal barrier coating is a kind of ceramic material deposited on the surface of superalloy substrate to protect the substrate material from high temperature erosion. Because of its good high temperature resistance, low thermal conductivity, and the thermal expansion performance matching with the substrate, it is widely used on the surface of high temperature parts such as aviation engine combustion chamber, which becomes an irreplaceable insulation material for modern aviation equipment (combustion chamber, airin duct, tailpipe, etc.). At present, yttria partially stabilized zirconia (YSZ) is mainly used in practice, while the long-term service temperature of YSZ ceramic material cannot exceed 1200 °C. In the field of aeronautics and astronautics, with the appearance and development of hypersonic vehicle, the surface temperature of its high-temperature components has far exceeded 1200 °C, the demand is close to 2300 °C, and the surface temperature of the coating has reached more than 1600 °C. The existing thermal barrier coating can no longer meet the ultra-high temperature demand of the weapon model, so it is necessary to develop a new type of thermal barrier coating with low thermal conductivity under ultra-high temperature conditions. Therefore, new ceramic coatings with low thermal conductivity, high thermal expansion coefficient, high temperature phase stability, low sintering rate and high temperature corrosion resistance have become the research focus and hot spot.In order to meet the urgent needs of the development of aerospace industry, new type of thermal barrier coatings materials of M0.02Gd0.025Yb0.025Y0.05Zr0.88 O1.94 (M= Dy, E, Eu, Sm, Nd) and N0.02Dy0.02Gd0.025Yb0.025Y0.05Zr0.86Ox (N=Ti, Mn, Si, Mg, Cr) with low thermal conductivity for ultra-high temperature were designed and synthesized by using zirconia with good comprehensive properties as the main material and doping rare earth and non rare earth elements as the solid solution system. The crystal structure and coating thermodynamic properties of the multi-doping system powders and coatings are systematically studied. The influences of ion radius and valences on the coating performance are studied. At the same time, combined with modern computer simulation technology, the temperature field change, thermal stress change and deformation of the coating in the ablation process were simulated to predict the most likely failure position of the coating. In order to further improve the performance of the coating, the pore structures of the coating were designed to improve the problem of thermal stress concentration of the coatings, and extend the service life of the thermal barrier coating, and improve the thermal insulation performance of the coating, and reduce the temperature to the base of the superalloy. The specific research contents and results are as follows:（1） Preparation and properties of binary ion doped (La1-xScx)2Zr2O7 powders and coatingsThe La2Zr2O7 coating with low thermal conductivity was modified by doping new elements. The effects of different content of Sc3+ ions on the thermal properties of the coating were studied by doping near rare earth Sc3+ ions with small radius. Scandium ion doping can reduce the thermal conductivity of lanthanum zirconate coating. When the content of Sc3+ is 0.1, the thermal conductivity of the coating is the lowest. The thermal conductivity of the Sc0.1 coating is 8.8% lower than that of the single La2Zr2O7 coating at 1600 °C.（2） Preparation and properties of ceramic powder and coating of M0.02Gd0.025Yb0.025Y0.05Zr0.88 O1.94A new type of quaternary M0.02Gd0.025Yb0.025Y0.05Zr0.88O1.94 ceramic powders was prepared by high temperature solid-state method. Moreover, the powder preparation process is simple, high output and stable performance, which is suitable for large-scale batch production. The NiCoCrAlY metal bonding layer with thickness of about 100 μm was prepared on the surface of Superalloy (GH4169) substrate by air plasma spraying, and the ceramic coating was prepared on the surface of the bonding layer. Compared with the YSZ coating, the new ultra-high temperature thermal barrier coating has better high temperature ablation resistance and lower thermal conductivity, which can be used as the ultra-high temperature thermal barrier coatings for aeroengine in the future.（3） Study on the preparation and properties of five element N0.02Dy0.02Gd0.025Yb0.025Y0.05Zr0.86 Ox doped modified ceramic powders and coatingsIn view of the poor thermal shock resistance of the above-mentioned four elements zirconia based thermal barrier coating, we further modified it by doping non rare earth oxides with low melting point. The modified five component ceramic coating prepared by solid-phase method not only keeps the advantages of the four components coating, but also improves the thermal shock resistance of the coating. Reducing the thermal conductivity of the coating, especially at 1600 °C, its thermal conductivity is 0.974 W/(m?K), which is 44.3% lower than the traditional YSZ (1.749 W/(m?K)) coating. Therefore, the modified new thermal barrier coating is an ideal choice for hot end components of aviation.（4） Pore structures design and thermodynamic properties of thermal barrier coatingsThe physical pore structure of the coating is designed on the basis of the existing coating. The theoretical calculation can optimize the coating pore structure with the lowest cost and the fastest speed, which will play a theoretical guiding role in the future coating structure design optimization. The results show that the coating with semicircular pore structure has the minimum strain, the best heat insulation performance and the minimum thermal stress. This is the first attempt and report to improve the coating performance by improving the physical pore structure of the coating.
|杨明. 低导热超高温热障涂层的制备及其性能研究[D]. 中国科学院大学,2020.|
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