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

The impact of moisture on flowability and spreadability is discussed. More notably we also present research on the impact of moisture on built nickel-base material. One lot of a newly opened Hastelloy X (HX) L‑PBF powder was split into two equal batches. One batch was moisturized using a programmable climate chamber, the other was untreated. We built bars with both batches for mechanical testing, in an EOS M100, with a cold build plate. The moisture content of the two powder batches, before and after the build-jobs, were determined using Karl Fischer titration (KF). Regarding the periodical monitoring of moisture content, it is not needed according to the findings of this paper. More moisture contributes to a slightly higher O‑content in the built material, and in turn, a very slight reduction in impact toughness. If a newly purchased powder exhibits poor flowability or high oxygen content, the analysis using oven-desorption followed by KF is recommended. If the moisture content is high, a drying of the powder is recommended.