Al-Ti-YSZ涂层的设计及其抗CMAS的机理

The improvement in efficiency, thrust weight ratio, and reliability of the aero-engine will be strongly dependent on the development of thermal barrier coatings (TBCs). However, CaO-MgO-Al2O3-SiO2 (CMAS) is the most dangerous factor that results in the failure of TBCs. The state-of-the-art YSZ coating has low thermal conductivity, good thermal shock resistance, and high stability. However, this coating cannot resist CMAS attack because the molten CMAS infiltrates the entire YSZ layer within extremely short period of time, leading to the spallation of TBCs. Doping YSZ with Al2O3 and TiO2 played an important role in inhibiting the phase transformation, yttrium depletion, and nucleation of micro-cracks of TBCs induced by CMAS attack, therefore enhancing the ability to resist CMAS corrosion. However, it is still not clear that how to design and control the constitution and microstructure of Al-Ti-YSZ coating, along with the preparation techniques that are valuable to its industrialization. Moreover, the mechanism of Al-Ti-YSZ coating resisting the CMAS attack also needs to be clarified. Based on the above issues, this project will systematically investigate the roles of Al2O3 and TiO2 in accelerating the solidification of molten CMAS, and analyze the reasonable composition proportion of Al-Ti-YSZ layer using thermodynamics of phase diagram. In addition, the project also aims to detect the sol-gel method of preparing the solution precursor of Al-Ti-YSZ coating, and analyze the deposition mechanism of this precursor during plasma spraying to optimize the preparation techniques. Furthermore, the mechanism of Al-Ti-YSZ coating resisting the molten CMAS corrosion at high temperature will be discussed on the basis of microstructure characterization, and the Al-Ti-YSZ coating with good resistance for CMAS attack together with its preparation techniques will also be achieved.

航空发动机效率、推重比和可靠性的任何进步将依赖于热障涂层的发展，高温CMAS腐蚀是涂层剥落的重要因素。目前应用最成熟的YSZ热障涂层热导率低、抗热震性好、热稳定性好，但抗CMAS能力差，熔融态的CMAS能很快渗透涂层并诱发剥落。在YSZ中加入Al2O3和TiO2能抑制CMAS引起的相变、Y的析出、裂纹形核，从而提高抗CMAS腐蚀的能力。然而，Al-Ti-YSZ涂层的成分、结构如何设计与控制，如何制备并得到可以产业化的工艺，抗CMAS的机理都还不清楚。基于此，本申请项目系统研究Al2O3和TiO2对CMAS凝固结晶的机制，基于相图热力学分析Al-Ti-YSZ涂层的成分配比，探索Al-Ti-YSZ前驱体的溶胶凝胶法制备方法，研究涂层液相等离子喷涂的沉积行为得到最优的制备工艺，并通过微观组织分析Al-Ti-YSZ涂层抗CMAS高温腐蚀的机理，得到抗CMAS性能优异的Al-Ti-YSZ涂层及工艺。

热障涂层广泛应用于航空发动机热端部件，降低基底表面温度，从而提高发动机效率。然而航空发动机在服役过程中，不可避免的摄入空气中的钙镁铝硅氧化物颗粒(CMAS)，导致涂层的成分、结构和性能等退化，最终涂层剥落失效。目前应用最广泛的7YSZ热障涂层材料极易遭到CMAS的腐蚀破坏，因此，有必要研究如何提高热障涂层抗CMAS腐蚀能力，同时不损害涂层本身其他优异性能。基于此，本项目通过Al2O3、TiO2对YSZ进行改性。结合反应热力学及性能分析，获得在不破坏自身性能前提下抗CMAS腐蚀的成分范围；通过腐蚀前后物相及微结构演变规律，进一步优化涂层成分，并制得涂层；协同相图计算，表面能分析及理论模型，分析涂层抗腐蚀机理。研究结果表明，Al2O3的加入能生成高熔点物质钙长石，堵塞CMAS入渗路径，增加CMAS入渗阻力，进而起到抗腐蚀作用，而TiO2的加入能促进钙长石的生成，从而降低了Al2O3的含量。且改性涂层的热、力学性能在一定程度上得到提升，表明Al-Ti-YSZ涂层在实际应用中具有重要意义。本项目的完成对于热障涂层抗腐蚀成分设计及机制研究具有指导意义。