在激光熔覆中，金属粉末粒子的运动情况直接影响熔覆的效果。由于金属粉末粒子的平均直径只有50 μm，同时因为其相互间碰撞，运动行为极其复杂，所以粒子的运动很难测量。讨论了应用数字粒子图像测速来对粒子的运动进行测量的方法，采用这种方法，可以通过两张具有一定时间间隔的图片来确定粒子流的位移矢量场。速度场可以通过位移场除以时间间隔得到，从而确定粉末流的汇聚角、发散角以及纵横方向的速度分布。结果表明，粒子测速方法可以满足粉末测速的需要，对激光熔覆工艺具有指导作用。

In laser cladding, the movement of the metal powder particles influences the cladding results directly. However, the movements of the metal powder particles are too hard to measure because the average diameter of the particles is about 50 μm and the movement behavior is very complex (collision of each other). The image process method based on digital particle image velocimetry (DPIV) technology is used to recognize the most particles. By this means, two images of the particle stream with a time interval are provided to determine the displacements of particles. Therefore, the velocity-vector field of the whole powder stream is obtained. Then, the convergence angle and the divergence angle of the powder flow can be measured by the velocity vectors, and the convergence region can be determined by the region of the maximum intensity of light. Results show that DPIV meets the needs of laser cladding and plays the role of guidance.