Statistical/Numerical Model of the Powder-Gas Jet for Extreme High-Speed Laser Material Deposition

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.

Development of powder delivery nozzles for laser gas-powder cladding

“…Недоліком даного метода є необхідність використання дзеркала з наріжним напиленням (для уникнення подвійного зображення) і не можливість його використання безпосередньо при реалізації ЛГПН. Зазначимо, науковці [20], [21] також розробили систему визначення параметрів сфокусованого ГПС, яка виконує поставлене завдання з "прецизійною" точністю. Недоліком даної системи та методу вимірювань є необхідність використання спеціального устаткування -лазера (формуючого "плоский" промінь працюючого в імпульсному режимі) та надшвидкої кінокамери, яка встановлена безпосередньо над соплом, яке формує ГПС.…”

Nozzle Designs in Powder-Based Direct Laser Deposition: A Review

“…5a) is a continuous coaxial nozzle design and the outward design (Fig. 5b) is the also known as an Extreme High Speed Laser Material Deposition (EHLA) nozzle [47].…”

“…However, this design has some limitations, too. In particular, the EHLA nozzle designs are not suitable for non-rotational depositions and cannot be employed with reflective materials, such as pure copper for example [47,53].…”

Special Issue on Surface Treatment by Laser-Assisted Techniques

“…The paper "Statistical/Numerical Model of the Powder-Gas Jet for Extreme High-Speed Laser Material Deposition" authored by Schopphoven et al describes the gas-powder stream modellization with practical application in laser cladding, and in additive manufacturing based on laser cladding (laser material deposition, LMD) [10]. This mathematical and experimental work considers coaxial powder delivery and spherical precursor material, and provides useful information for the prediction of precursor particle trajectories and particle-radiation interactions in the jet and laser beam intersection volume.…”