Formation Mechanism and Physical Properties of Particle Ejection during Laser Cutting of Metal Alloys

Abstract

Micro-scale particle ejection, an inevitable second emission during laser cutting of metal alloys, leads to significant hazards to operators’ lung and workpiece’s surface quality. This study established a Multiphysics numerical model to investigate the formation mechanism and physical properties of the ejected particles. An incompressible Newtonian laminar non-isothermal multiphase fluid flow was modelled for the laser-metal interaction process by implementing the governing equations, sources terms representing the laser energy and dynamic assist gas pressure, and melting and solidification effect. The volume of fluid (VOF) method, together with dynamic mesh adaption, was employed to track the metal-air interface of the two-phase fluid model. The physical formation phenomena of particles ejected from the kerf front were illustrated by the temperature and morphology evolution history. The dynamic behaviour of the ejected particles was revealed by their shape, size and velocity distribution over time using VOF-to-DPM technique. The effect of laser power and assist gas pressure on the equivalent diameter and velocity of the ejected particles were further studied quantitively to assist the development of subsequent exhaustion systems for secondary emissions. The developed numerical model takes a step forward in understanding the mechanics at the kerf regions and assisting the development of subsequent exhaustion systems for secondary emissions during laser cutting of high-end components.