抗熔融CMAS腐蚀的梯度Y2O3改性ZrO2热障涂层的设计及其功能实现机制

Thermal barrier coatings (TBCs) technology is one of the key technologies for blades in advanced aero-engines. With the development of engines with high thrust-to-weight ratio, the turbine operating temperatures have exceeded the melting point of engine environmental deposits (The main compositions are CaO, MgO, Al2O3 and SiO2, or CMAS for short). As a result, the coating performance degradation and premature spallation caused by molten CMAS become the bottleneck problems of the service life and reliability of TBCs applied on turbine blades. Especially for TBCs prepared by EB-PVD, the infiltration of molten CMAS is accelerated due to the typical columnar intergranular gaps. In recent work, our group has found that the modification using rare earth oxides can effectively improve the coating resistance to CMAS corrosion. However, the protection mechanism is still unclear and the influence on thermal cycle life of TBCs should be also urgently studied. In view of this, a design thought of novel gradient thermal barrier coating with high Y2O3 content on the top and low content on the bottom is proposed in this project. The design and preparation methods will be mastered through study. The effect mechanisms of the gradient coating on preventing corrosion by molten CMAS and on thermal cycle life will be revealed. And the optimization method of coating structure by PA EB-PVD will be established. These will lay the theoretical foundation for the development of long-life TBCs with good CMAS corrosion resistance at high-temperatures.

热障涂层（TBCs）是先进航空发动机叶片的关键技术之一。随着高推重比航空发动机的发展，发动机工作温度已经超过了环境沉积物（主要成分为CaO、MgO、Al2O3和SiO2，简称CMAS）的熔点，导致由熔融CMAS引起的涂层性能退化和过早剥落，成为影响发动机叶片热障涂层服役寿命和可靠性的瓶颈。特别是对EB-PVD制备的TBCs而言，其特有的柱状晶间隙会加速熔融CMAS的渗入。本项目团队近期研究发现，稀土改性可以有效提高涂层抗CMAS腐蚀能力，但其作用机理尚不明确，对涂层热循环寿命的影响也亟待研究。鉴于此，本项目提出一种表层富Y2O3、底层低Y2O3的梯度热障涂层设计思路，拟通过研究掌握梯度Y2O3改性ZrO2涂层的设计和制备方法，阐明梯度涂层阻熔融CMAS腐蚀的作用机理和对热循环寿命的影响机理，建立梯度涂层的PA EB-PVD结构优化方法，为长寿命抗高温CMAS腐蚀TBCs的研制提供理论指导。

随着高推重比航空发动机的发展，发动机工作温度越来越高，一种由环境沉积物（主要成分为CaO、MgO、Al2O3和SiO2，简称CMAS）引起的腐蚀成为发动机叶片热障涂层（TBCs）失效的主要模式。特别是对EB-PVD制备的TBCs而言，其特有的柱状晶间隙会加速熔融CMAS的渗入。现有的CMAS防护方法存在增加制备工序、提高成本和引入新界面增加失效风险的问题，鉴于此，本项目开展了梯度Y2O3改性ZrO2热障涂层设计、制备和实现机制研究，为长寿命抗高温CMAS腐蚀TBCs的研制提供了理论指导。.研究了熔融CMAS在EB-PVD YSZ涂层表面的铺展、渗透过程以及对涂层的腐蚀行为，建立了CMAS在柱状晶涂层表面铺展、渗透的动力学模型，揭示了涂层受CMAS腐蚀的失效机制。CMAS的铺展、渗透可分为粘度控制、结构控制和孔隙率控制三个阶段。随着温度升高，铺展和渗透速度越快。CMAS通过与YSZ反应，消耗掉稳定元素Y，从而改变涂层的结构、热物理性能和相稳定性，造成涂层发生分层、鳞片状或整体剥落。.设计了梯度Y2O3改性ZrO2涂层材料，掌握了Y2O3含量对ZrO2块材热物理、力学性能的影响规律，阐明了CMAS对不同Y2O3含量改性ZrO2涂层材料的腐蚀机理。通过比较8YSZ、25YSZ、50YSZ、75YSZ的相组成、热导率、硬度、断裂韧性以及1250℃下的抗CMAS腐蚀性能等，确定了梯度涂层表层Y2O3的临界含量应为~50wt.%。.研究了梯度Y2O3改性ZrO2涂层的EB-PVD制备技术，掌握了梯度涂层成分和结构的调控方法。通过设计特殊结构的陶瓷靶材，结合EB-PVD工艺参数调控，制备出了表面Y2O3含量达到50wt.%，30μm后逐渐减少到8wt.%的梯度涂层。.评估了梯度涂层抗熔融CMAS腐蚀性能，揭示了梯度涂层1250℃下的抗CMAS腐蚀机制。与传统8YSZ涂层相比，梯度涂层面层富Y，可以与熔融CMAS在柱晶间隙等部位发生反应，生成磷灰石等高熔点的阻挡相，延缓CMAS的进一步下渗，从而提高抗CMAS腐蚀性能。.优化了梯度涂层的结构，建立了梯度涂层的结构优化方法。采用等离子激活EB-PVD工艺实现了梯度涂层的结构优化，相比于传统EB-PVD涂层，优化后的涂层柱状晶结构更加细小、致密，抗CMAS腐蚀能力进一步提高。

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