强制对流作用下CNTs-TiC复合增强涂层的制备及其凝固组织控制研究

This project is based on the way of material surface modification and composite, using carbon nanotubes synthesized on iron surface in carbonaceous atmospheres at high temperatures as carbon source and reinforced phase. With the help of the forced convection and rapid solidification of laser melt pool, the CNTs-TiC composite reinforced phase will be prepared in situ and distributed uniformly in the coating by the stabilizing control of the reactions where the optimum processing parameters are determined using an artificial neural network model..The non-equilibrium solidification behaviour, microstructure evolution and formation, and interfacial microstructure of the reinforced phase will be examined by the study of interactions between in situ reaction and solidification process. The optimization technology for controlling solidification structure will be developed based on the solidification structural shape factor and the relationship between the laser processing parameters and the shape factor. Combining the performance data, the relationship between the structure and properties of the composite will be revealed. The reinforcing and toughening mechanisms of composite are investigated by using advanced materials analysis techniques and the experiment results from corrosion and wear tests. .The aim of this work is to provide the guidance for design, development and application of Fe-base surface composites.

本项目基于材料表面改性及复合的思路，采用在高温碳气氛中铁基材料表面自生碳纳米管作为碳源和增强相，借助激光熔池的强制对流和快速凝固的特点，在人工神经网络模型的指导下优化激光工艺参数，协同和控制反应稳态进行，从而实现涂层中CNTs-TiC复合增强相的原位合成和均匀化分布。.本项目通过对强制对流作用下原位合成反应与凝固过程交互作用的研究，揭示熔池中增强相的非平衡凝固行为、相的形成、组织演变规律及界面微观结构特征；对凝固组织形状因子的影响因素以及激光工艺参数与形状因子之间的关系进行研究，探索控制凝固组织的最佳工艺；结合实验性能数据，建立材料性能与显微组织结构间的构效关系；在通过腐蚀、磨损等实验基础上，结合现代材料分析测试先进技术，揭示复合材料的强化机制。.本研究将为铁基表面复合材料的设计、开发及应用提供指导。

本项目采用在高温碳气氛中铁基材料表面自生碳纳米管作为碳源和增强相，借助激光熔池的强制对流和快速凝固的特点，在304不锈钢和Q235普碳钢表面获得了原位合成的CNTs-TiC增强的涂层。探索了增强相的原位自生机理、增强相结构与材料性能之间的关系，重点考察其腐蚀性能和冲蚀性能，进而揭示了铁基表面复合材料的强韧化机制。.项目如期完成了申请书的研究内容并得到以下研究成果：.1. 通过对激光熔覆反应体系的稳态控制、工艺参数优化与建模，在钢基材料表面原位自生了CNTs-TiC增强相，并制备了相应的铁基表面复合材料。.2. 在304不锈钢表面涂层组织中均匀分布着大量的TiC、Cr7C3和CNTs增强相，粘接相为(Fe, Ni)固溶体。另外在涂层顶层观察到易碎的TiO2-TiC陶瓷层。然而Q235普碳钢表面涂层分为明显的内层和外层两层，外层主要是以TiC和TiO2组成的陶瓷外层，内层是由CNTs-TiC作为增强相和(Fe, Ni) 固溶体作为粘接相组成的金属陶瓷内层。在铁基体上获得的激光熔覆涂层都呈现出连续，致密和具有优良结合力的特征。涂层的平均硬度远高于基本的平均硬度。.3．采用304不锈钢作为对比材料，在1mol/L的HCl溶液中对涂层的耐腐蚀性能进行了研究发现：304不锈钢表面的TiC-Cr7C3-CNTs涂层耐蚀性能远高于304不锈钢，且没有观察到不锈钢常见的严重点蚀。对于Q235普碳钢表面涂层的腐蚀性能而言：涂层外层和内层都优于304不锈钢且外层又优于内层。 同样，也没有观察到涂层的点蚀。.4．通过模拟海洋环境的冲刷腐蚀研究发现，涂层比304不锈钢基体具有较优异的冲蚀性能。