Drying strategies to reduce the formation of hydrogen porosity in Al alloys

EasyChair Preprint 973

Abstract

Laser powder bed fusion (L-PBF) is an additive manufacturing (AM) technology using a high-power laser to selectively melt metal powders for building complex parts. Coping with contamination in the powder is usually a challenge for this technology. Gases entrapped in the material in contact with the laser create a plasma of impurities that can lead to porosity. This contamination is usually coming from moisture, organics and adsorbed gases from the atmosphere (i.e. oxygen and nitrogen). In this work, two drying strategies to reduce the formation of porosity will be investigated. The first strategy consists of drying the metal powder outside the SLM Solutions machine under vacuum for 18h at 70°C to avoid powder contamination. The second strategy applies the strategy of drying the powder in the AM by scanning it with 90W laser power prior to the melting process. Samples were printed with either both strategies applied, one of them or none, giving four different conditions. During the L-PBF process, the laser power was set to either 350 W (low) or 380 W (high). An assessment of the porosity and density obtained from the AlSi10Mg metal blocks after applying the two drying strategies and built with L-PBF is presented. The porosity was characterized in terms of pore shape and size as well as its distribution throughout the blocks. The microstructure is revealed to study the location of the pores which leads to a discussion of the pore formation. The proposed drying strategies provide an alternative for reducing powder contamination and achieving process repeatability.

Keyphrases: Additive Manufacturing, Al alloys, AlSi10Mg, L-PBF (Laser Powder Bed Fusion), drying, moisture

@booklet{EasyChair:973,
  author    = {Laura Cordova and Ton Bor and Mónica Campos and Tiedo Tinga},
  title     = {Drying strategies to reduce the formation of hydrogen porosity in Al alloys},
  howpublished = {EasyChair Preprint 973},
  year      = {EasyChair, 2019}}