Abstract
Extreme high-speed laser material deposition, known by its German acronym EHLA, is a new variant of laser material deposition (LMD) with powdered additives. This variant’s process control is unlike that of LMD, where the powder melts as it contacts the melt pool. In the EHLA process, the laser beam melts the powder above the surface of the substrate to deliver a liquid to the melt pool. At a given intensity distribution in a laser beam, the heating of powder particles in the beam path depends largely on the three-dimensional powder particle density distribution (PDD) and the relative position within the laser beam caustic. As a key element of a comprehensive numerical process model for EHLA, this paper presents a statistical/numerical model of the powder-gas jet, as previously published in Experimentelle und modelltheoretische Untersuchungen zum Extremen Hochgeschwindigkeits-Laserauftragschweißen. The powder-gas jet is characterized experimentally and described with a mathematical model. This serves to map the PDD of the powder-gas flow—and particularly the particle trajectories for different grain fractions—as well as the powder mass flows and carrier and inert gas settings, to a theoretical model. The result is a numerical description of the particle trajectories that takes into account the measured particle size distribution with calculations made on the assumption of a constant particle velocity and linear trajectories of the particles.
Highlights
Laser material deposition (LMD) is a process by which a laser beam creates a melt pool on the surface of a substrate while a powder nozzle delivers a powdered additive to the processing point–that is, into the melt pool
There is the extreme high-speed laser material (EHLA) process in which a large share of the particles are to be extreme high-speed laser material (EHLA) process in which a large share of the particles are to be fully fully melted by the laser beam before they arrive in the melt pool Tp > TM, or (Ts − Tp) < 0 [1,4,5,6,7]
Unlike control for for laser material deposition (LMD), LMD,where wherethe thepowder powdermelts meltsasas contacts melt pool, in Unlike the the process process control it it contacts thethe melt pool, in the the process, the laser beam melts the powder above the surface of the substrate to deliver a EHLA process, the laser beam melts the powder above the surface of the substrate to deliver a liquid liquid to the melt pool
Summary
Laser material deposition (LMD) is a process by which a laser beam creates a melt pool on the surface of a substrate while a powder nozzle delivers a powdered additive to the processing point–that is, into the melt pool. To produce a metallurgically bonded layer that is free of defects, the laser power, feed rate, powder mass flow and other process parameters have to be configured so as to apply sufficient process heat to trigger a suitable temperature–time cycle for the base material and additive. This application of heat goes to create a melt pool on the substrate surface and ensures that the additive melts fully. Melted by the laser beam before they arrive in the melt pool Tp > TM , or (Ts − Tp ) < 0 [1,4,5,6,7]
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