3D Shape Analysis of Powder for Laser Beam Melting by Synchrotron X-ray CT

Abstract

The quality of components made by laser beam melting (LBM) additive manufacturing is naturally influenced by the quality of the powder bed. A packing density <1 and porosity inside the powder particles lead to intrinsic voids in the powder bed. Since the packing density is determined by the particle size and shape distribution, the determination of these properties is of significant interest to assess the printing process. In this work, the size and shape distribution, the amount of the particle’s intrinsic porosity, as well as the packing density of micrometric powder used for LBM, have been investigated by means of synchrotron X-ray computed tomography (CT). Two different powder batches were investigated: Ti–6Al–4V produced by plasma atomization and stainless steel 316L produced by gas atomization. Plasma atomization particles were observed to be more spherical in terms of the mean anisotropy compared to particles produced by gas atomization. The two kinds of particles were comparable in size according to the equivalent diameter. The packing density was lower (i.e., the powder bed contained more voids in between particles) for the Ti–6Al–4V particles. The comparison of the tomographic results with laser diffraction, as another particle size measurement technique, proved to be in agreement.

3D Computed Tomography Quantifies the Dependence of Bulk Porosity, Surface Roughness, and Re‐Entrant Features on Build Angle in Additively Manufactured IN625 Lattice Struts

“…The Ni‐based alloy Inconel 625 [ 20 ] was used for L‐PBF production of seven struts with different build angles α from 30° to 90° in steps of 10° (see Figure a), all other production parameters being the same. α was defined as the angle between the build baseplate and the nominal strut (cylinder) axis.…”

Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges

“…In Section 3.2, excessive laser power was found responsible for the creation of gas bubbles in the molten pool which are then trapped in the material during solidification. Another source of gas is associated with the metal powder, see Thiede et al [168], particularly if the packing density of the latter is low [83]. There is an extensive range of process parameters which affect the degree of porosity, besides the above mentioned laser power and power density, these are scan speed, spot size, scan strategy, powder size, powder morphology and others [86,169].…”

Classification of Defect Types in SLM Ti-6Al-V4 by X-ray Refraction Topography

“…This deviation from a spherical shape can also be recognized from a 3-D sphericity analysis of the SXCT reconstructions. 19,31 The sphericity (defined as…”