反应等离子合成纳米晶TiCN复合涂层的研究

Nanocrystalline TiCN coatings were prepared by reactive plasma spraying in this project. Graphite or carbon black powders were used as the carbon source and mixed with micron Ti powder homogeneously to prepare composite powders suitable for plasma spraying. The composite powders were then fed to the nitrogen-containing high temperature plasma flame, in which micron Ti reacted with C and N to form TiCN. Adjusting the proportion of C/Ti of the composite powders and changing the design of spray gun to improve the flow of N2 plasma gas and make the N2 adjustable within a certain range in the plasma flame, which resulted in the reaction products with different C: N ratio, i.e. TiN → TiCxN1-x → TiC. The grain shape and grain size under different C/N ratio and different powers were investigated, and the effect of carbon on the crystallization law and the formation law of nanocrystalline were revealed. The properties of the coatings under different C/N ratio were investigated, and the priority of the formation of TiN or TiC under plasma spraying conditions was investigated by thermodynamic calculations. Combined with the quenching product of different spray distances, the reaction between Ti, C and N and the formation mechanism of TiCN were revealed. The purpose of this project is to provide a theoretical basis for the preparation of high performance nanocrystalline coatings and promote the research of crystallization law under the undercooling conditions. The as-prepared coatings have a wide application in the fields of metallurgy, petroleum, chemical industry, electricity, machinery and marine development.

本课题采用反应等离子喷涂的方法制备纳米晶TiCN涂层的思路，制备TiCN纳米晶涂层。课题以石墨或炭黑粉为碳源与微米级Ti粉混合制备成适于喷涂的复合粉，送入含氮的高温等离子焰流，在焰流内微米级Ti与 C、N发生自蔓延反应形成TiCN。通过调整复合粉中C、Ti比例和通过改变喷枪设计提高N2离子气的最大流量，使焰流内的N2在一定范围内可调，通过对N2气的调节，得到由TiN→TiCxN1-x→TiC不同C：N比的反应产物，研究各C：N比下晶粒形态和大小，不同功率条件下晶粒的大小，得出C对结晶规律影响及纳米晶的形成规律；研究不同C：N比涂层的性能；通过热力学计算得出喷涂条件下TiN、TiC得出二者优先形成的可能性，结合不同喷涂距离的淬熄产物，研究TiCN的反应及形成机制。项目研究的目的是为制备高性能纳米晶涂层提供理论依据，促进深过冷条件下结晶规律的研究。该涂层在冶金、石油、化工、电力等具有广泛前景。

本课题采用反应等离子喷涂的方法制备纳米晶TiCN涂层的思路，制备TiCN纳米晶涂层。课题以石墨或炭黑粉为碳源与微米级Ti粉混合制备成适于喷涂的复合粉，送入含氮的高温等离子焰流，在焰流内微米级Ti与 C、N发生自蔓延反应形成TiCN。本课题的主要研究内容为：1）选择了合适的碳源、确定了粉末粒度。采用喷雾造粒法制备了适于喷涂的C、Ti复合粉末优化了制粉工艺；研究了复合粉的开始燃烧温度； 2）研究了不同C:Ti比制备涂层相组成、形貌及涂层性能，优化了复合粉的C:Ti比和制备涂层的工艺参数；3）实现了TiCN涂层制备过程中C、N含量的调控，通过控制粉末成分和工艺参数可得到由TiN→TiCxN1-x→TiC不同C：N比的反应产物，不同比例涂层硬度可在13GPa到32GPa调控，达到了通过控制制备参数调控涂层组织性能的目的。4）研究了涂层的结晶规律。涂层中的晶粒以柱状晶为主，配以少量的等轴晶，TEM结果显示涂层以纳米晶为主，并存在少量非晶。随涂层中C含量的增加晶粒尺寸减小。XRD衍射结果表明随涂层C含量的增加（111）面占据了竞争生长的优势。5）研究了TiCN涂层形成的反应机制。得出等离子喷涂过程中首先形成了TiC，在枪距40~60mm之间N参与反应形成TiN，在随后的飞行过程中形成TiCxN1-x。6）通过第一性原理计算和XPS进一步确定了涂层中的相组成和反应生成的规律。7）研究了涂层的磨损和电化学腐蚀。得到了C:N比涂层磨损规律和电化学腐蚀规律。.本项目通过对反应产物结晶规律和反应机制的研究，为实现多元材料的组织结构调控提供了理论依据；提供了一种高熔点超硬纳米材料的制备方法，为纳米材料、超硬材料用于结构材料提供了新的途径。.项目发表论文11篇，其中被SCI收录8篇，EI收录2篇；申报发明专利3项；培养博士生1名，硕士生4名；参加学术会议5人次。