Modeling of laser beam and powder flow interaction in laser cladding using ray-tracing

Laser cladding, also known as direct metal deposition, is an additive manufacturing technique for the production of freeform metallic parts. In the laser cladding process, a high-power laser beam is directed onto the surface of a solid metallic workpiece while a jet of metallic powder is focused into the beam through a coaxial nozzle. The heating of the workpiece is governed by the laser light that is being absorbed, so that detailed simulations of the laser cladding process require an accurate knowledge of the light intensity pattern that reaches the workpiece after interaction with the powder jet. In the past, several statistical distributions have been proposed for modeling this intensity pattern. However, these require strong simplifications of the powder particle trajectories and do not take into account the complex powder flow profile that is present in practical systems. In this paper, the effect of the powder flow on the incident laser intensity is numerically studied under varying process conditions. A finite element simulation of the powder flow is performed and used to generate a set of powder particle trajectories using Monte Carlo simulation. A ray-tracing algorithm is developed to split the laser beam into multiple rays of light which get partly reflected and absorbed by the particles and the workpiece. Running the ray-tracing procedure over time allows the calculation of an averaged incident light intensity pattern as well as an averaged pattern of the energy absorbed by the particles that arrive at the workpiece. Several simulations are performed in order to study the effects of the used laser intensity pattern and the particle size distribution. The results are in good agreement with existing literature.