ONLINE INVESTIGATION OF THE HARD PARTICLE -TRANSPORT DURING LASER DISPERSING USING HIGH-SPEED RADIOSCOPY

At the Institute of Material Science (IW) at the University of Hannove r, investigations were carried out in close contact with the laser Zen trum Hannover (LZH) and the Institute of Nuclear Engineering and Non-D estructive Testing concerning the particle transport processes during loser dispersing of predeposited hard particle layers. To gain an exte nded process understanding of the beam/material interaction with respe ct to the transport processes within the molten pool, microfocus-radio scopy was used in combination with a high-speed video camera. The vide o data (determination of particle paths) was analysed using an image p rocessing system. In this paper the test and analysis equipment for th e observation of particle transport processes and results concerning s tationary laser dispersing of predeposited hard particles will be desc ribed. The process monitoring system is, for the first time, suitable for observing the mass flow within the molten pool. With respect to th e flow direction, two flow fields with opposite directions and centers close to the edge of the molten pool could be proved using radioscopy of the interaction zone perpendicular to the laser beam. The flow at the surface is from the center to the edge of the molten pool, then al ong the side to the bottom center. From there the flow is upwards to t he surface.