Effect of layer thickness on spatter properties during laser powder bed fusion of Ti–6Al–4V

Abstract

High layer thicknesses for laser powder bed fusion are promising for productivity increase. However, these are associated with increased process instability, spatter generation and powder degradation, crucial for alloys sensitive to oxygen. The effect of increasing layer thickness from 30 to 60 µm is studied focusing on Ti-6Al-4V spatter formation during LPBF and its characterisation, with scanning and transmission electron microscopy, combustion analysis and X-ray photoelectron spectroscopy. Results indicate that spatters are covered with a uniform Ti-Al-based oxide layer and Al-rich oxide particulates, the thickness of which is about twice that present on virgin powder. The oxygen content was about 60% higher in spatters compared to the virgin powder. The study highlights that increasing the layer thickness to 60 µm permits to reduce the total generation of spatters by ∼40%, while maintaining similar spatter characteristics and static tensile properties. Hence, this allows to increase build rate without compromising process robustness.

Reuse of Smoulder in Laser Powder-Bed Fusion of AlSi10Mg—Powder Characterization and Sample Analysis

“…In the case of stainless steel, chemical composition and crystal structure appear to remain unchanged throughout the transformation from virgin powder to smoulder [20]. For Ti6Al4V, one study detected no change in composition [25] and one study did [26]. However, smoulder particles form a thicker oxide layer than virgin powder counterparts, but this does not affect the bulk properties of particles [27].…”

“…However, smoulder particles form a thicker oxide layer than virgin powder counterparts, but this does not affect the bulk properties of particles [27]. The thickness of oxide layers on IN718 smoulder particles decreases with lower oxygen content during the build job [25]. Murray et al [28] found an influence of smoulder content on single-track volumes which is rather negligible if it is blended with virgin powder [24].…”