Surface plasmon induced enhancement in selective laser melting processes

Abstract

Purpose Selective laser melting (SLM) is an advanced rapid prototyping or additive manufacturing technology that uses high power density laser to fabricate metal/alloy components with minimal geometric constraints. The SLM process is multi-physics in nature and its study requires development of complex simulation tools. The purpose of this paper is to study – for the first time, to the best of the authors’ knowledge – the electromagnetic wave interactions and thermal processes in SLM based dense powder beds under the full-wave formalism and identify prospective metal powder bed particle distributions that can substantially improve the absorption rate, SLM volumetric deposition rate and thereby the overall build time. Design/methodology/approach We present a self-consistent thermo-optical model of the laser-matter interactions pertaining to SLM. The complex electromagnetic interactions and thermal effects in the dense metal powder beds are investigated by means of full-wave finite difference simulations. The model allows for accurate simulations of the excitation of gap, bulk and surface electromagnetic resonance modes, the energy transport across the particles, time dependent local permittivity variations under the incident laser intensity, and the thermal effects (joule heating) due to electromagnetic energy dissipation. Findings Localized gap and surface plasmon polariton resonance effects are identified as possible mechanisms toward improved absorption in small and medium size titanium powder beds. Furthermore, the observed near homogeneous temperature distributions across the metal powders indicates fast thermalization processes and allows for development of simple analytical models to describe the dynamics of the SLM process. Originality/value To the best of the authors’ knowledge, for the first time the electromagnetic interactions and thermal processes with dense powder beds pertaining to SLM processes are investigated under full-wave formalism. Explicit description is provided for important SLM process parameters such as critical laser power density, saturation temperature and time to melt. Specific guidelines are presented for improved energy efficiency and optimization of the SLM process deposition rates.

Laser subtractive and laser powder bed fusion of metals: review of process and production features

“…The relatively high beam quality M 2 ≈1, of modern fiber laser, allows it to be focused over a relatively long distance with a relatively long focal depth (beneficial for deep cuts and holes) (Rai et al , 2007; Mahrle et al , 2010). The absorptivity also depends on the polarization state (parallel or perpendicular) of the laser light and the direction of cutting (C-Costa-Rodrigues, 2018; Genov and Vinnakota, 2019). The maximum cutting speed is obtained when the direction of cutting is parallel to the polarization plane.…”