钛基稀土激光熔覆层中TiC的生长规律研究

Study on Growth Rule of TiC in Ti-base Laser Cladding Layer with Rare Earth

利用同步送粉激光熔覆技术在Ti811表面制备了TC4+Ni45+WC+CeO2激光熔覆层。利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱分析仪(EDS)分析了涂层的组织和相组成,分析了制备过程中的反应机理,利用显微硬度计测试了涂层的显微硬度。结果表明,涂层的α-Ti基底中分布有枝晶Ti C、纳米共晶Ti C(缺位型TiCx)、TiB2和金属间化合物Ti2Ni等相;通过对比发现,加入CeO2的激光熔覆层生成相密度明显增加,晶界密度明显增大,晶界强化特征明显,枝晶TiC粒径相对粗大,涂层中二次析出的纳米共晶Ti C依附于枝晶Ti C生长,形成了纳米共晶TiC+枝晶TiC的复合相结构;涂层的显微硬度高于基底的,涂层的最高硬度为697 HV0.5,较基底提高了约0.8倍。

TC4+Ni45+WC+CeO2 laser cladding layer was prepared on the surface of Ti811 by synchronous powder feeding laser cladding technology.The microstructure and phase composition of the coating were tested by XRD,SEM and EDS.The reaction mechanism in preparation process was analyzed.The microhardness of the coating was measured by microhardness tester.The results show that dendritic TiC,nano-eutectic TiC(TiCx),TiB2 and Ti2Ni intermetallic distribute in theα-Ti substrate of the coating.By contrast,the phase density of the laser cladding layer added with CeO2 is obviously increased,the grain boundary density is obviously increased,the characteristics of grain boundary strengthening are obvious,the dendrite TiC is coarse,and the second precipitated nano-eutectic Ti C in the coating grows adhering to the dendrite Ti C,forming a composite phase structure of nano-eutectic TiC and dendritic TiC.The microhardness of the coating is higher than that of the substrate,the highest hardness of the coating is 697 HV0.5,which is about 0.8 times higher than that of the substrate.