Abstract
Moisture is often regarded as one of the main reasons for poor processability of powders using Laser-powder bed fusion (L-PBF) processes. To determine the influence of moisture on the spreadability, a superalloy powder IN718 commonly used for L‑PBF processes has been conditioned in two different states: once in the as-received and dry condition and once in a moist condition obtained by storing the powder for four weeks in an atmosphere containing a relative humidity of 75%. Using a self-built spreading tester and a subsequent analysis method specially developed for testing the spreadability of a powder, the differently conditioned IN718 powder batches have been investigated regarding the surface roughness and flatness of the powder layers. Additionally, the formation of empty spots between the powder particles in the top layer has been studied.
Highlights
Nickel-based superalloys combine high-temperature strength, toughness, corrosion resistance, and good fatigue life, which is why they are widely used in the aerospace and energy industries [1,2,3]
An initial powder characterization to determine whether or not a powder is suitable for a build job has always been of particular interest, due to the high cost and long duration of such a build job
Of particular interest is the flowability of a powder, whereby a distinction must be made between flow time and flowability
Summary
Nickel-based superalloys combine high-temperature strength, toughness, corrosion resistance, and good fatigue life, which is why they are widely used in the aerospace and energy industries [1,2,3]. Of particular interest is the flowability of a powder, whereby a distinction must be made between flow time and flowability The former is measured by means of a calibrated Hall funnel, and the latter refers to the totality of various measurable variables that are combined to describe the complex behaviour of powders when mobilised, such as flow time, and, for example, cohesiveness, particle size and shape, and others [4, 5]. Apart from these well-known powder properties, new testing methods are available as well [6,7,8,9]. Assessing this quantitatively is of high practical importance, it is a challenging job
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