等离子熔覆TiB_2长条+TiC颗粒多尺度复合强化陶瓷涂层

TiB_2 strip + TiC particles multiscale strengthing phase for ceramic composite coatings by plasma cladding

以Ti、Fe、B4C为初始粉末,采用等离子熔覆的方法,在Q235低碳钢表面获得了Fe基Ti B2长条、Ti C颗粒等多尺度强化相的陶瓷涂层,并分析了涂层的物相组成、组织结构、显微硬度,探讨了物相、组织结构的形成过程。结果表明,涂层主要物相为Ti B2、Ti C、Fe2B、Fe3(C,B)和α-Fe,其中Ti B2主要为长条状,长度为60~74μm,少部分呈近六边形块状,尺寸为4~5μm,而Ti C主要是不规则的多边形细小颗粒,尺寸2~3μm,均匀地分散在涂层中,还有部分Ti C呈枝晶状;涂层与基体之间存在过渡层,涂层与基体之间结合紧密,呈冶金结合;随着等离子束电流的增加,长条状的Ti B2数量减少而近六边形的块状Ti B2数量增加,Ti C枝晶生长更加充分。因Ti B2长条和细小的Ti C颗粒共存,对涂层起到多尺度复合强化作用。

A kind of Fe-based ceramic coatings with Ti B2 strips and Ti C particles as multi scale strengthening phases on the surface of Q235 steel were fabricated by plasma cladding using Fe,Ti and B4 C powder mixture as precursor. The phase composition,microstructure and microhardness of the coatings were investigated. The microstructure evolution and the formation of the phase were discussed. The results show that the coatings are composed of Ti B2、Ti C、Fe2B、Fe3( C,B) and α-Fe phases. Ti B2 phase is mainly in the shape of strip with length of 60-74 μm,and a small amount phase is in shape of quasi-hexagonal with size of 4-5 μm. Most of the Ti C particles are irregular polygon shape with size of 2-3 μm,dispersed in the coating homogenously. Some of the Ti C particles are dendrite shape. Furthermore a transition layer between coating and substrate is formed. This is benefit to improve the bonding strengthening between surface coating and substrate to produce a dense and strong metallurgical interface. With the increasing of plasma beam current,the amount of strip-like Ti B2 can decrease,but quasi-hexagonal Ti B2 increase. At the same time,Ti C dendrites develop fully. Thus,the composite coating is reinforced by the multi-scale and coexisting of Ti B2 strip and small Ti C particles.