Simplified numerical model for the laser metal deposition additive manufacturing process

Abstract

The laser metal deposition (LMD) laser technique is a free-form metal deposition process, which allows generating near net-shape structures through the interaction of a powder stream and a laser beam. A simplified numerical model was carried out to predict layer heights together with temperature distributions induced by the (LMD) process on a titanium alloy, and a metal matrix composite. Compared with previously developed models, this simplified approach uses an arbitrary Lagrangian Eulerian free surface motion directly dependent on the powder mass feed rate Dm. Considering thin wall builds of Ti-6Al-4V titanium alloy, numerical results obtained with comsol 4.3 Multiphysics software were successfully compared with the experimental data such as geometrical properties of manufactured walls, fast camera molten pools measurements, and thermocouple temperature recordings in the substrate during the manufacturing of up to 10 LMD. Even if the model did not consider coupled hydraulic-thermal aspects, it provides a more realistic local geometrical description of additive layer manufacturing walls than simpler thermal models, with much shorter calculation times than more sophisticated approaches considering thermocapillary fluid flow. In a second step, microstructures (equiaxed or columnar) were predicted on Ti-6Al-4V walls using microstructural map available in the literature, and local thermal gradients G (K/m) and solidification rate R (m/s) provided by the FE calculation near the solidification front. © 2017 Laser Institute of America.