Ti-B_4C-C系在火焰喷涂时的SHS过程

SHS Process of Ti-B_4C-C Reactive System in Flame Spraying

以Ti-B4C-C为反应喷涂体系,依托SHS反应火焰喷涂制备TiC-TiB2复相陶瓷涂层技术,通过水淬熄实验,截取了喷涂过程中飞行不同距离的粒子,观测了不同飞行距离下,中间状态反应产物的宏观特征、成分和组织结构及其变化过程,理论探讨了复合粉体在氧-乙炔火焰焰流中的飞行燃烧过程与反应机理。研究表明,中间状态的反应产物按其宏观特征出现了完全熔融的实心陶瓷液滴、完全熔融的空心陶瓷液滴、表面熔融芯部未熔的陶瓷颗粒和完全未熔的陶瓷颗粒4种。其飞行燃烧过程机理是:SHS反应始于钛粉的熔化,对位于火焰焰流芯部的中小尺寸喷涂团聚颗粒,其燃烧合成受扩散和毛细管机制控制,以爆燃方式进行;对位于火焰焰流外围的较大尺寸喷涂团聚颗粒,其燃烧合成受组元熔解析出机制控制。

Based on the SHS Reactive Flame Spray technology, TiC-TiB2 multiphase ceramic coatings were prepared in the Ti-B4C-C reactive system. Water quenching experiments were used to intercept the intermediate states of the flying particles during the spray course. The macroscopical characteristics, composition, structure, and transforming course of the intermediate-stated reactive products in different flying distance were observed, and the flying combustion course and reactive mechanism of the spray agglomerates in the oxyacetylene flame were discussed. It was showed that there were four types of intermediate-stated reactive products according to their macroscopical characteristics, which were the fully molten solid and hollow ceramic beads, the ceramic particles with molten surface whereas the un-molten core and the completely un-molten ceramic particles. The flying combustion mechanism is studied. The SHS reaction began with the melting of Ti powders. The combustion synthesis of the relatively small spray agglomerates in the core of the oxyacetylene flame was controlled by the diffusion and capillary mechanism and took place in the deflagration mode, whereas the combustion synthesis of the relatively big spray agglomerates in the periphery of the oxyacetylene flame was controlled by the ingredient melting and separating out mechanism.