基于组织优化和活性元素协同作用提高热喷涂MCrAlY涂层抗高温氧化性能的机制研究

Thermal sprayed MCrAlY coating plays an important role in high temperature protection of hot components of aircraft engine and the ground gas turbine. In order to improve the high temperature performance of thermal sprayed MCrAlY coating, A pulse detonation-plasma technology which provides a superimposition effect of multiple energy was first adopted to modify the surface of thermal sprayed MCrAlY coating. The new technology can not only make the microstructure refinement and densification, but also add beneficial alloy elements, such as rare earth、 Re and Ta into the coating. Therefore, the synergetic enhancement effect of performance improvement and utilizing the reactive effect was simultaneously obtained to control the formation and growth and evolution of TGO，which is a key factors (grown characteristic of thermally grown oxides(TGO))affecting the service life of the coating was put forward. By the way, the oxidation resistance of MCrAlY coating was improved. In this project, the aim is to investigate the mechanism of the microstructure evolution and electrode alloy elements penetration. Furthermore, the mechanism of improved oxidation resistance was also illustrated from the aspect of growth dynamics, phase structure, adhesion, and stress state of thermally grown oxide. Based on the above result, the relational model of surface modification technology- microstructure state-oxidation resistance were established. The investigation will lay an experimental and theoretical foundation for controlling the grown characteristic of TGO and improvement of the service life of the thermal sprayed high temperature protective coating.

热喷涂法制备的MCrAlY涂层在航空发动机和燃气轮机高温部件的防护领域起着至关重要的作用。为了进一步提高热喷涂MCrAlY涂层的抗高温氧化性能，本项目拟采用具有多重能量耦合特性的新型脉冲爆炸-等离子体技术对涂层进行改性处理，该技术不但能实现涂层组织细化和致密化，还能向涂层中添加稀土元素、Re、Ta等活性合金元素，可通过组织优化和活性元素效应两者的协同作用对影响涂层服役寿命的关键因素-热生长氧化物（TGO）的生长和演变行为进行有目的的干预和控制。项目拟研究涂层微观组织的演化机制及合金元素在涂层中的渗入机制，从TGO的生长动力学、相结构、粘附性、应力状态等方面阐明涂层表面TGO的生长和演变机制，最终建立表面改性技术-涂层微观组织-高温氧化性能之间的关系模型。研究结果将为TGO的受控生长、提高热喷涂高温防护涂层的使用寿命奠定实验和理论基础。

热喷涂法制备的MCrAlY涂层在航空发动机和燃气轮机热端部件的高温防护领域起着至关重要的作用。项目首次采用脉冲爆炸-等离子体（PPD）方法对等离子喷涂CoNiCrAlY涂层进行表面改性处理，利用有限元方法模拟计算了改性处理过程中涂层表层的温度场和应力场。研究了涂层改性层组织特征和演变机制，阐明了改性涂层抗高温氧化性能提高的机制。结果表明，在优化的工艺参数下经过PPD改性处理后，涂层表面粗糙度降低，表层氧化物、孔洞等缺陷消失，形成了晶粒尺寸约为20-50nm的致密改性层。在改性层内，Ta元素的渗入深度为8μm，最大浓度为5.98wt%，Dy元素的渗入深度为4μm，最大浓度为4.61wt%。有限元模拟表明，涂层表层升降温速率为107K/s，约20μm深度范围内温度达到熔点，热应力值最大达6.7Gpa。多次重熔和热应力的叠加作用是改性层组织致密化、细化和元素渗入的主要原因。脉冲爆炸-等离子体改性处理消除了涂层表层缺陷，向涂层中添加了有益元素Ta，提高了Al2O3膜的粘附性，抑制了尖晶石氧化物的过早形成，提高了涂层的抗高温氧化性能。研究结果将为发展新型热喷涂涂层表面改性方法奠定实验和理论基础，还可为其他合金材料提供一种新的表面强化方法。