激光表面合金化制备TiC/Ti复合涂层的组织与性能

利用激光表面合金化技术在工业纯钛表面制备TiC/Ti复合涂层,并对复合涂层的组织与性能进行了分析和测试,对TiC的合成机理进行了探讨.研究结果表明,复合涂层由合金化层和热影响区组成.合金化层由TiC和α′-Ti构成,TiC的生长形貌包括树枝状、十字花瓣状、胞枝状以及针状,热影响区主要由α-′Ti构成.合金化层的平均显微硬度为HV 420.TiC的合成过程分为三个阶段:激光辐照时,固态C颗粒迅速扩散至激光熔池并被液态Ti包围;首先固-液结合界面处的Ti和C直接反应形成TiCx,随后液Ti扩散并穿过TiCx层与剩余的C进行反应,直至TiCx中C的浓度达到TiC中C的浓度,生成的TiC溶于液相中;快速凝固过程中,TiC从溶液中析出并长大.

Microstructure and property of TiC/Ti composite coating by laser surface alloying

TiC/Ti composite coating was fabricated by laser surface alloying on pure industrial titanium surface.The microstructure and property of this coating was analyzed and measured.The synthesis mechanism of TiC was explored.The results showed that TiC/Ti composite coating was consisted of alloyed layer and heat affected zone.The alloyed layer contained TiC and Ti(martensite),and the heat affected zone contained Ti(martensite).TiC growth morphologies had a well-developed dendrite,cellular dendrite,acicular and cross-petal microstructure.Micro-hardness of the laser surface alloyed layer was improved up to HV 420. The synthesizing process of TiC can be divided into three periods: diffusion,reaction and rapid solidification.First,carbon particle diffused quickly into laser melting pool during laser radiation.Then,the molten titanium surrounded the carbon particle and reacted at its outer interface,thereafter the molten titanium diffused through TiC_x layer to react with the unreacted portion of the carbon particle,and TiC dissolved in the liquid phase.Finally,TiC precipitated from liquid phase and grew during the rapid solidification process.