A variant of conventional laser material deposition (LMD), extreme high-speed laser material deposition (German acronym: EHLA) is characterized by elevated process speeds of up to 200 m/min, increased cooling rates, and a significantly reduced heat affected zone. This study focuses on the feasibility of using EHLA to apply material onto Fe-based substrate materials with AISI 4340 as a filler material. We studied how three different build-up strategies—consisting of one, three, and five consecutive deposited layers and hence, different thermal evolutions of the build-up volume—influence the metallurgical characteristics such as microstructure, porosity, hardness, and static mechanical properties. We propose a thermo-metallurgical scheme to help understand the effects of the build-up strategy and the thermal evolution on the microstructure and hardness. The tensile strength of the build-up volume was determined and is higher than the ones of forged AISI 4340 material.
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.
Retracted: “Numerical Studies of Extreme High-Speed Laser Material Deposition Processes at Powder-Scale” [ASME 2019 International Mechanical Engineering Congress and Exposition, Volume 2A: Advanced Manufacturing, Salt Lake City, Utah, USA, November 11–14, 2019, Conference Sponsors: ASME, ISBN: 978-0-7918-5937-7, Copyright © 2019 by ASME. Paper No. IMECE2019-10730, pp. V02AT02A045; 10 pages; doi: 10.1115/IMECE2019-10730]
