钛表面激光碳合金化与TiC生长分析

Analysis of the growth mechanism of TiC crystal and the mechanical properties of the laser alloyed layer on the surface of pure titanium

利用激光对预涂石墨粉的纯钛(TA2)进行表面熔凝处理。并用扫描电镜、电子探针、X射线衍射和高分辨电子显微镜等分析手段知其合金化层内生成了大量的枝状TiC,发现枝状TiC是由类似块状晶线性排列组成。理论分析了枝状TiC晶体的生长机制是经过连续生长和侧面生长两阶段的生长过程形成的。性能测试表明,其表面硬度较基体大为提高,且摩擦系数较基体明显降低。激光工艺参数影响合金化层的组织性能,选择适宜的工艺参数方能获得理想的表面合金化层。

The laser-alloyed layer is fabricated on the surfac e of pure titanium with graphite powder. The microstructures and phase constituent s of the alloyed layers are investigated by means of SEM,EPMA,XRD and HRTEM. T he results show that a great deal of dendritic TiC crystals are formed in the al loyed layer.The growth mechanism of dendritic TiC crystals is theoretically anal yzed,at first they continuously grow into dentritic TiC embryo crystals and then each of them acts as many nucleuses on which the lateral growths begin. So the final morphologies of dendritic TiC crystals look as if they were composed of cr ystallitic grains in a linear arrangement. The test results show that the hardne ss of the alloyed layers is much higher than that of the matrix and the wear coe fficient of alloyed layers is significantly lower than that of the substrate. Ch anging laser processing parameters can greatly affect the microstructures and me chanical properties of the alloyed layers,ideal alloyed surface can be achieved only if optimum parameters selected.