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. Highlights Increased layer thickness from 30 to 60 µm resulted in ∼40% lower amount of spatter generated per build Increased layer thickness from 30 to 60 µm resulted in ∼17% higher amount of generated spatter per scanned layer Increase in bulk oxygen content by >60% was registered for spatter compared to the virgin powder in both cases The oxide layer is about twice thicker on the spatter particles compared to virgin powder.