Abstract
The Laser Metal Deposition (LMD) process is an additive manufacturing method, which generates 3D structures through the interaction of a laser beam and a gas/powder stream. The stream diameter, surface density and focal plan position affect the size, efficiency and regularity of the deposit tracks. Therefore, a precise knowledge of the gas/powder streams characteristics is essential to control the process and improve its reliability and reproducibly for industrial applications. This paper proposes multiple experimental techniques, such as gas pressure measurement, optical and weighting methods, to analyze the gas and particle velocity, the powder stream diameter, its focal plan position and density. This was carried out for three nozzle designs and multiple gas and powder flow rates conditions. The results reveal that (1) the particle stream follows a Gaussian distribution while the gas velocity field is closer to a top hat one; (2) axial, carrier and shaping gas flow significantly impact the powder stream’s focal plan position; (3) only shaping gas, powder flow rates and nozzle design impact the powder stream diameter. 2D axisymmetric models of the gas and powder streams with RANS turbulent model are then performed on each of the three nozzles and highlight good agreements with experimental results but an over-estimation of the gas velocity by pressure measurements.
Highlights
The recent notion of Rate Per Flight Hour (RPFH) business in aeronautics sectors leads to a wide development of repairing technics for aircrafts maintenance to offer a stronger, faster and cheaper process
Four experimental techniques were investigated to analyze the characteristics of the gas and powder streams under multiple gas and powder flow rates conditions three coaxial Laser Metal Deposition (LMD)
Results showed that an increase in the axial and shaping gas flow rate significantly pulls down the focus plane position, while an
Summary
The recent notion of Rate Per Flight Hour (RPFH) business in aeronautics sectors leads to a wide development of repairing technics for aircrafts maintenance to offer a stronger, faster and cheaper process. The typical patterns of powder density and particle temperature distributions were found to be dependent on the coaxial nozzle type by Kovalev et al [20] Considering all these works, it can clearly be established that the nozzle design and gas parameters have a strong impact on the powder flow density, speed and trajectory, and directly influence the powder stream characteristics and the clad efficiency [21]. Multiple experimental technics exist to describe the powder stream structure and characteristics but the influence of process parameters such as gas flow rate (Dg ), standoff distance (WD ) and nozzle design have rarely been studied numerically and compared with experimental data. Special attention was paid to the determination of particle’s velocity, trajectory, powder stream diameter, density and focal plan position
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