激光-感应复合熔覆“微合金化-CNTs”复合增强铜基涂层微结构与高强高导协调机制

The protective coatings with high quality are adopted to increase the lifetime of copper crystalliaztion roller, which has become a problem to be solved urgently in the field of strip casting. To eliminate the delamiantion failure of coatings produced by the traditional techniques, and overcome the common problems such as low efficiency of laser cladding and cracks of cladding layer, the technique of microalloying-CNTs hybrid reinforced copper-based coatings produced by laser-induction hybrid cladding has been put forward by us. Under the condition of cladding efficiency can be increased to 1~5 times higher compared to individual laser cladding, the formation mechanisms of nickle covering copper-based alloy powder with a dispersive distribution of CNTs, and CNTs/copper-based coatings prepared by laser-induction hybrid cladding are systemically investigated. The effects of hybrid cladding parameters, micro-alloyed composition, content and diameter of carbon nanotubes (CNTs) on the microstructural evolution and properties (i.e., strength, wear, corrosion and thermal conductivity) are deeply studied. Moreover, the thermodynamic and kinetic conditions of precipitation growth and the heat transfer behavior in the interface of CNTs and copper alloy matrix are analyzed in detail. This project is successfully carried out, which can make for furhter understanding a series of scientific problems, suh as the relationship of microstructural control with crystalline orientation and crack susceptibility, and so on. Additionally, this project can also provide the solid theory and practical foundation for establishing the coordinatin mechnism between the microstructural control and high-strength, high-conductivity properties, understanding the physical mechanism of microalloying-CNTs hybrid reinforced copper-based coatings produced by laser-induction hybrid cladding, controlling the quality of CNTs/copper-based coatings and developing the new coatings.

采用高质量涂层提高铜结晶辊使用寿命，成为了薄带连铸技术亟待解决的关键问题。针对常规法制备的涂层易脱落，及激光熔覆效率低与熔覆层易开裂的难题，本项目提出激光－感应复合熔覆"微合金化－CNTs"复合增强铜基涂层的新方法，在加工效率提高1~5倍的条件下，系统研究镍包覆CNTs弥散分布的铜合金粉末的形成机理与CNTs/铜基涂层的制备，深入研究复合熔覆工艺参数、微合金化成分、CNTs含量与直径对微结构演变与性能（强度、耐磨、耐蚀、传热）的影响，CNTs与铜合金基体界面析出相生长的热力学与动力学条件，CNTs/铜基涂层界面传热行为。本项目的顺利实施，有助于进一步认识微结构调控与晶体取向、生长特征、裂纹敏感性之间的关系等科学问题，为建立微结构与高强高导性能的协调机制，理解"微合金化－CNTs"复合增强铜基涂层激光－感应复合熔覆的物理机制，控制CNTs/铜基涂层质量及发展新型涂层奠定坚实的理论与实践基础。

采用高质量涂层提高铜结晶辊使用寿命，成为了薄带连铸技术亟待解决的关键问题。针对常规法制备的涂层易脱落，及激光熔覆效率低与熔覆层易开裂的难题，本项目提出激光－感应复合熔覆“微合金化－CNTs”复合增强铜基涂层的新方法，在加工效率提高1~5倍的条件下，系统研究镍包覆CNTs弥散分布的铜合金粉末的形成机理与CNTs/铜基涂层的制备，深入研究复合熔覆工艺参数、微合金化成分、CNTs含量与直径对微结构演变与性能（强度、耐磨、耐蚀、传热）的影响，CNTs与铜合金基体界面析出相生长的热力学与动力学条件，CNTs/铜基涂层界面传热行为。当采用优化工艺参数，如激光能量密度445J/m2、粉末面密度为600g/m2、感应加热温度为873K、CNTs含量为2.6wt.%时，获得铜基复合涂层性能如下：热导率197 W m-1 K-1，硬度429HV0.2，摩擦系数0.11，磨损率5.3×10－16 m3 N-1　lap-1。