用高能集中横流式的二氧化碳激光束作为诱导热源，在铸钢表面进行改性处理，形成了含有碳氮化钛增强粒子的铁基熔覆层。利用X射线衍射仪（XRD）、电子探针（EPMA）、扫描电镜(SEM)、能谱仪（EDX）、透射电镜（TEM）和选区电子衍射花样（SAED）等手段对复合熔覆层的微观结构及它们中第二相粒子的成分、形貌和尺寸进行了分析和研究。试验结果表明：先前加入的颗粒状TiN与石墨粉在激光熔覆过程中发生了化合反应，原位生成了新的颗粒状Ti（C_0.3N_0.7）强化相。复合熔覆层的基体组织由树枝胞状晶α–Fe和Ti（C_0.3N_0.7）颗粒硬质相共同组成，新相Ti（C_0.3N_0.7）颗粒的形貌特征多呈不规则形状，大小在0.1～6.0 μm之间，它们较均匀地弥散分布在熔覆层α–Fe基体上。硬质相颗粒Ti(C_0.3N_0.7)与熔覆层基体α–Fe之间结合紧密，界面干净光滑。

A new in–situ synthesis method is carried out to produce Fe–based alloy composite coating reinforced by Ti（C_0.3N_0.7）particle on the surface of cast steel through CO₂ laser cladding technology. X–ray diffraction (XRD) is used for phase identification that is in the composite coating. The microstructure of laser cladding layer is analyzed by means of electron probe microscopy analyzer (EPMA), scanning electron microscopy (SEM), energy dispersive X–Ray spectrometer（EDX), transmission electron microscopy (TEM) and selected area electron diffraction（SAED）.The results show that Ti（C_0.3N_0.7）particle is introduced by an in–situ metallurgical reaction of TiN particle and graphite powder during laser cladding process. The shape of Ti(C、N) particle is irregular, and they are dispersed evenly in the matrix. Size of particles is within 0.1～6.0 μm. The substrate of laser cladding layer contains martensite microstructure, which is fine dendritic and cell crystal. A new kind of phase named Ti（C_0.3N_0.7）particles are tightly bonded with α–Fe microstructure with a clean and smooth interface between them.