激光-感应复合作用下纳米YSZ/Ni核壳粒子的熔凝行为及界面反应机理研究

The surface of some key engine components to be protected and repaired rapidly should be urgent to solve and laser cladding nano-ceramic coatings is an effective way. However, the application of the technology is limited due to the re-agglomeration and burning loss of nanoparticles during laser cladding. In the research, nano-YSZ(yttria stabilized zirconia)/Ni core-shell particles will be used to improve the dispersion of nano-YSZ particles and avoid the burning loss of nano-YSZ particles during laser induction hybrid cladding. Both the relative experiments and numerical simulation are carrid out to investigate the temperature variation in the coating region and to establish the temperature field during laser induction hybrid cladding. The dispersion of nano-YSZ particles in the coating and the melting and solidification behaviours of the nano-YSZ particles in the laser pool and the interface of solid-liquid are investigated. Then the melting and solidification behaviours of nano-YSZ/Ni core-shell particles during laser induction hybrid cladding process are discussed. The interface microstructure and interfacial reaction products of the laser induction hybrid cladding nano-ceramic coating are studied. The formation mechanism of coating is discussed and the interface reaction model is established. The research mainly aims at discovering the solidification behaviour and interface intereaction mechanism of nano-YSZ/Ni core-shell particles during laser induction hybrid cladding process, which can promote the technique of laser induction hybrid cladding nano-ceramic coatings applying in the field of the surface protection and repairing of key components with wear resistance or resistance to high temperature corrosion. The present study can form a theoretical and technical basis for preparing a nano-ceramic coating with high performance by laser induction hybrid cladding.

激光熔覆纳米陶瓷涂层是解决航空发动机关键零部件表面的快速保护和修复等问题的有效途径。然而，纳米陶瓷在激光熔覆过程中的团聚和烧损等关键问题是制约纳米涂层性能的主要瓶颈。本项目以激光-感应复合熔覆纳米Y2O3部分稳定的ZrO2（简称为YSZ）作为研究对象，利用核壳式纳米YSZ/Ni复合粒子来改善纳米YSZ的分散性、防止其在熔覆过程烧损。采用实验和数值模拟相结合的方法，分析涂层各区域温度变化规律，建立复合熔覆过程温度场；研究纳米YSZ/Ni复合粒子在涂层中的分布，探究其在熔池中的流动、凝固，阐明纳米YSZ/Ni核壳粒子的熔凝行为及其与复合热源的作用机制；系统研究涂层中相界面的精细结构及界面反应产物，揭示涂层形成机制，建立界面反应模型。本项目的顺利实施，有助于加快激光-感应复合熔覆技术在耐磨损、耐高温腐蚀等关键零部件表面的快速保护和修复领域中应用，为该技术制备高性能纳米陶瓷涂层奠定理论和技术基础。

激光熔覆纳米陶瓷涂层是解决航空发动机关键零部件表面的快速保护和修复等问题的有效途径。然而，纳米陶瓷在激光熔覆过程中的团聚和烧损等关键问题是制约纳米涂层性能的主要瓶颈。本项目以激光熔覆纳米Y2O3部分稳定的ZrO2（简称为YSZ）作为研究对象，利用核壳式纳米YSZ/Ni复合粒子来改善纳米YSZ的分散性、防止其在熔覆过程烧损。采用先单层后多层，并结合温度场模拟讨论了纳米YSZ@Ni核壳粒子的激光熔凝行为及涂层的形成机制。结果表明，经激光熔凝后纳米YSZ在熔覆层中分布成四种状态，除了在枝晶末端、镶嵌在晶界颗粒状及少量团聚态的“花状”YSZ外，最主要形成了YSZ/FeCr2O4共晶组织；然而，壳层Ni扩散进入热影响区，形成Fe、Cr、Ni三元合金过渡层，改善了熔覆层与Fe-Cr合金基体之间的相容性和润湿性；在此基础上进行了多层熔覆，纳米YSZ在熔覆层中主要以YSZ/FeCr2O4共晶组织形式存在，且熔覆层数越多，涂层组织越均匀，显微硬度也更高；同时发现，多层熔覆对纳米YSZ/(FeCr2O4)共晶组织的粗细有双重影响，多层熔覆可使熔池升温而增加液体过冷度，利于细化共晶组织；但熔覆层数过多，晶粒生长速度加快，导致组织粗化。利用第一性原理和分子动力学构建了激光熔凝过程界面反应模型。研究了工艺参数及NiCoCrAlY粘结粉末加入量对涂层组织和性能的影响，并利用热应力耦合分析涂层的应力场分布规律，讨论涂层制备过程中的裂纹形成机理，为获得高性能的涂层进行理论指导。结果表明：在铺粉厚度0.5mm、光斑直径3mm、搭接率50%、激光熔覆功率1000W、扫描速度360mm/min的工艺条件下，激光熔覆NiCoCrAlY0.3/YSZ@Ni（1-0.3）热障涂层的组织致密，抗氧化性较好。本项目的研究成果，有助于加快激光熔覆技术在耐磨损、耐高温腐蚀等关键零部件表面的快速保护和修复领域中应用，为该技术制备高性能纳米陶瓷涂层奠定理论和技术基础。