Particle image velocimetry in thermal spraying

In thermal spraying processes, the particle velocity is an important influence parameter with respect to the coating properties. Additionally, the analysis of the particle velocities in many cases enables a better understanding of the process. Consequently, suitable diagnostic methods for the measurement of particle velocities meeting the requirements in the area of thermal spraying processes are needed. One diagnostic method being field-tested is the laser-optical particle image velocimetry (PIV) method. In this paper, the concept of the PIV system and analysis methods for PIV images are presented. Furthermore, short descriptions of the two common thermal spraying processes high velocity oxygen-fuel flame spraying (HVOF) and atmospheric plasma spraying (APS) are given. The influences on the kinetics of an HVOF- and an APS-process obtained by means of PIV are described. In this context, it has to be pointed out that PIV is qualified for measurements of particle velocities in thermal spraying processes.