Influencing the powder particle transport in high-speed laser melt injection

Using high-speed laser melt injection (HSLMI), it is possible to generate wear-resistant metal matrix composite (MMC) surfaces on tools with great productivity. Since high laser intensities are required for reaching high process speeds, strong interactions can occur between powder particles and the laser beam. In order to reduce the interaction time and gain a better understanding of the role of particle transport in the HSLMI process, trajectories of spherical fused tungsten carbide (SFTC) particles were analyzed using high-speed imaging. The trajectories were divided into a path outside the laser beam and a path inside the laser beam. The identified interaction mechanisms were particle deformations, the formation of agglomerates, and particle disintegration. The volume flow rate of the feeding gas was found to have a decisive influence on the travel time of the particles, whereas the powder feed rate and the working distance of the powder nozzle only had a minor influence. Consequently, an increased volume flow rate led to a significant reduction of interactions between SFTC particles and the laser beam.