Investigations of aging behaviour for aluminium powders during an atmosphere simulation of the LBM process

Abstract

Additive layer manufacturing (ALM) offers for production of parts and components for aeronautical applications potential cost benefits over conventional manufacturing routes. In particular, powder bed processes offer a high degree of design flexibility while enabling weight reduction due to topological optimisation. The quality and properties of the parts are strongly dependent on the powder quality which, in turn, is influenced by handling and storage of the powder. For this reasons an undefined contamination of atomised powder materials by oxygen and hydrogen has to be avoided. Aluminium-silicon powder was aged under atmosphere of different moistures and temperatures for defined duration. The effect of these environments as well as the effect of vacuum drying on the flowability was investigated. The morphology was evaluated by scanning electron microscope. The chemistry including oxygen content of the powder was measured by inductively coupled plasma optical emission spectrometry and hot fusion analysis.

Measuring the spreadability of pre-treated and moisturized powders for laser powder bed fusion

“…3). The results in [33] show that even for these very spherical particles an increasing humidity level leads to a significant decrease in the flowability of the powder (which in this work was concluded from an increase in the avalanche angle and avalanche time in a Revolution Powder Analyzer test). The reduced flowability is also in this work attributed to a higher agglomeration rate due to higher moisture content and hydrogen bonds.…”

“…It could be argued that the observed high level of water absorption in AlSi10Mg, as compared to the three other powder alloys, is due to the less spherical shape of the particles in the AlSi10Mg powder used here. However, Bauer [33] investigated AlSi10Mg powder atomized by the Electrode Induction Melting Gas Atomization (EIGA) process, which resulted in a very spherical morphology. A moisturizing treatment at 23.7 °C and 84.2 % rH for 72 h was applied to the EIGA atomized powder, which is similar to the conditions applied in the present study (Fig.…”

Moisture in Metal Powder and Its Implication for Processability in L-PBF and Elsewhere

“…Especially aluminium powders (AlSi10Mg and Scalmalloy) were strongly affected compared to others (IN718 and Ti6Al4V) [1]. Bauer [2] reported similar findings for AlSi10Mg0.45 and AlSi7Mg0.6. In a follow-up paper Cordova et al [3] showed that moisture affected the layer density, but only to a strong degree for AlSi10Mg.…”

Infrared Spectroscopy Studies of Aluminum Oxide and Metallic Aluminum Powders, Part I: Thermal Dehydration and Decomposition

“…Similar studies have been completed for various types of aluminas; however, to the best of our knowledge we have not seen a study performed in situ with aluminum powders [14]. The ability to prepare aluminum powder surfaces for improved chemical receptivity is of interest to a wide variety of industrial, medical, and academic applications where the surface state is critical for the final product properties [15]. This is especially relevant in additive manufacturing where the powder is typically recycled [16].…”

“…Thermal treatment has been utilized to decompose these phases into the more reactive phase boehmite and to liberate the hydrogen bond surface hydroxyls. This is particularly relevant to metallurgical processing and additive manufacturing, where the surface hydroxides and oxides can interfere with the final product [28]; additionally, surface aging can interfere with flow properties impeding proper powder distribution [15].…”