Characterization of ultrafine particles emitted during laser-based additive manufacturing of metal parts

Abstract

Particulate matter (PM) emitted during laser additive manufacturing with stainless steel powder materials has been studied in detail. Three different additive manufacturing techniques were studied: selective laser melting, direct metal deposition and laser cladding. Gas flow and temperature fields accompanying the processes were numerically modeled for understanding particle growth and oxidation. Transmission and scanning electron microscopy were used for primary particle and PM characterization. The PM collected in the atmosphere during manufacturing consisted of complex aggregates/agglomerates with fractal-like geometries. The overwhelming number of particles formed in the three processes had equivalent projected area diameters within the 4–16 nm size range, with median sizes of 8.0, 9.4 and 11.2 nm. The primary particles were spherical in shape and consisted of oxides of the main steel alloying elements. Larger primary particles (> 30 nm) were not fully oxidized, but where characterized by a metallic core and an oxidic surface shell.

Characterisation of Particles Emitted during Laser Cutting of Various Metal Sheets and an Exposure Assessment for the Laser Operators

“…The collected particles show typical morphologies associated with thermal-generated condensation particles. The agglomerates/aggerates were often a mixture of agglomerates of loosely bound spherical primary particles ( Figure 3 A) and/or sintered or coalesce primary particles forming aggregates ( Figure 3 B,C), which is similar to the findings in Noskov et al [ 7 ]. The size and shape of particles will depend on the relative rates of particle collision and coalescence.…”

“…Additionally, α-Fe was determined in the SS and BKS samples. Metallic Fe has earlier been observed in the core of condensation particles collected during additive manufacturing [ 7 ]. When particles are exposed to air at room temperature, an oxide shell will instantly be formed [ 30 ].…”

“…Condensation particles formed during thermal processes have been well characterised by welding [ 5 ], laser additive manufacturing [ 6 , 7 , 8 , 9 ], and in metal fume from other industrial production processes [ 10 , 11 ]. Generally, these particles are ultrafine agglomerates/aggregates of condensates.…”

Comprehensive Analysis of Two H13-Type Starting Materials Used for Laser Cladding and Aerosol Particles Formed in This Process

“…These primary particles then aggregate or agglomerate to form larger particles that can penetrate deep into the lungs. The nanoparticle emission of laser-DED machines has been recognized, and some studies have already addressed the chemical and physical characterization of the emitted particles [ 10 ] and investigated occupational health-related issues [ 5 , 11 ]. The toxic properties of metal nanoparticles are now well known [ 5 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] and their effects need to be taken into account in working environment design and laser-DED machine construction.…”

Characteristics, formation mechanisms, and control methods ​of emissions from 3D printing​

“…It was found that airborne nanoparticles (4-16 nm) were observed inside the enclosure or at the ventilation outlets of the printers. These particles consisted of oxides of the main steel alloying elements as shown in Figure2.21[83].…”