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.
Highlights
Particulate matter (PM) emitted during laser additive manufacturing with stainless steel powder materials has been studied in detail
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 for EOS M 270 dual mode, InssTek MX-Mini and laser cladding (LC)-10 IPG-Photonics, respectively
Compared to previous research of laser ablation of metals where a maximum of the particle size distribution at 6–11 nm, dependent on laser intensity, were observed, the sizes of the primary particles in the laser additive processes studied in this work are s imilar[32]
Summary
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. During the development of additive manufacturing technology there have been numerous different terms and definitions in use, often with reference to specific application areas and trademarks This is often ambiguous and confusing which hampers communication and wider application of this technology[1]. The EOS Company has patented a process that is called as “Direct Metal Laser Sintering (DMLS)”, while the Fraunhofer Institute introduced their own term “SLM” for Selective Laser Melting. These two techniques are based on similar principles, to avoid any confusion we will use unified term “PBF-LB/M” according to ISO s tandards[2]. It has shown that nanometer-sized particles were present at relatively high number air concentrations in the additive manufacturing environment (Graff et al, 2016; Ljunggren, 2019)[24,25]
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