Abstract
Moisture is often claimed to be one of the main reasons for poor processability of powders when using L‑PBF processes. To determine the influence of moisture on the processability, gas atomized superalloy powder IN718 has been printed in two parallel runs: once in the as-received and dry condition and once after four weeks of storage in an atmosphere containing a relative humidity of 75%. Thereby different specimens have been prepared for notched impact tests, tensile tests, roughness, and metallographic analysis. Furthermore, the chemical composition of the powder before and after the build job as well as that of the printed parts have been analysed. The results obtained with the differently conditioned powders have been compared in the end to determine the influence of humidity on the processability on IN718 powder.
Highlights
Nickel-based superalloys have been widely used in the aerospace and energy industries and, as they are difficult to process in particular through machining, near-netshape processing techniques, such as additive manufacturing of these materials, have gained more and more popularity over the last decades [1, 2]
It is assumed that the adaptation of the powder to the atmosphere caused by the change in relative humidity of the air when taking a sample out of the container for analysis happens so rapidly that much of the water has already been—more or less uncontrollably—desorbed at the time of measurement
This is concluded to be the main reason why there are no differences in any tests caused by the various conditioning states of the L718 AMPO powder used
Summary
Nickel-based superalloys have been widely used in the aerospace and energy industries and, as they are difficult to process in particular through machining, near-netshape processing techniques, such as additive manufacturing of these materials, have gained more and more popularity over the last decades [1, 2]. These materials combine high-temperature strength, toughness, corrosion resistance, and good fatigue life [3]. Apart from the particle size and shape of a powder, which can influence powder characteristics such as the flowability, adsorbed water on the powder surface is often claimed as detrimen-
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