Causes and Measures of Fume in Directed Energy Deposition: A Review

Abstract

Pores and cracks are known as the main defects in metal additive manufacturing (MAM), including directed energy deposition(DED). A gaseous fume is often produced by laser flash (instantaneous high temperature) during laser processing, which may cause various defects such as porosity, lack of fusion, inhomogeneity, low flowability and composition change, either. However the cause and harmful effects of fume generation in DED are known little. In laser processing, especially laser welding, many studies have been conducted on the prevention of fume because it generates defects that hinder uniform reactions between the laser beam and the materials. Generally, the fume occurs with easily vaporizing low melting point components or sensitive oxidizing elements. Unsuitable conditions are also known to have an effect, including laser power, travel speed, powder feed rate and shielding gas supply. Practically, there are many more fume generating factors in the DED process, and the lack of understanding requires a lot of trial and error. In this article the laser-related and weld metallurgy literatures were reviewed, focusing on the prevention of fume in powder DED. The causes of the fume, were explained to result from the stages of cavitation bubbles generated by the laser induced plasma and the nanoparticles released. Additionally, the effects of alloying components and environmental conditions for fume generation in the DED process were investigated, and suggestions are proposed to prevent fume.

Preventing Evaporation Products for High-quality Metal Film in Directed Energy Deposition: A Review

“…Hence, the material did not deposit completely, and spatter was present at the beam boundary. Figure (b) gives an example of good results on a singletrack [118]. Therefore, an experiment to control the hatch distance in a multi-track experiment can produce a better-deposited layer than a single-track.…”

The state of 3D printing technologies: A review

“…Laser cladding known to offer many advantages for modern application, as when parameters are properly set the quality reach a very good level. Howeover, DED 3D printed objects have high porosity and poor mechanical properties [24,25]. DED categories are laser engineered net shaping (LENS), aerosol jet technology, electron beam additive manufacturing (EBAM), laser deposition welding (LDW), and wire and Arc additive manufacturing (WAAM).…”