Systematic investigation of performance and productivity in laser powder bed fusion of Ti6Al4V up to 300 µm layer thickness

Abstract

Within the realm of metal additive manufacturing, laser powder bed fusion (PBF-LB) has maintained a dominant role by offering exceptional geometric freedom, fine feature resolution and fine microstructure features. However, low productivity still presents a bottleneck in the adaptation of PBF-LB in most industrial contexts. In recent literature, build-up rates have shown to improve notably when thicker powder layers are employed. However, systematic analyses linking processing parameters, productivity, microstructural state and mechanical properties are lacking. This study aims to fill this gap for Ti6Al4V alloy with powder layer thicknesses in the range of 60 µm to 300 µm, specifically using system-agnostic process parameters applicable to the majority of currently available commercial AM systems. The results revealed that Youngs modulus (∼110 GPa) and yield strength (∼1.1 GPa) remain comparable to ‘conventional’ PBF-LB Ti6Al4V throughout the investigated range of layer thickness. At the same time elongation to failure decreases from 11.4 ± 2.7% at 60 µm to 8.4 ± 1.1% at 180 µm and finally to 2.0 ± 0.3% at 300 µm, which was microscopically correlated with increased occurrence of lack-of-fusion porosity in layers exceeding 180um. It was also demonstrated that the changes in the parent β phase texture arising from process changes could have contributed to decreased ductility at thicker layers. Ultimately, while productivity increases with layer thickness up to 8.76 mm3/s at 300 µm, the achievable build rate appears to plateau around 300 µm layer height and require further expansion of the laser power characteristics to enable additional gains without compromising mechanical performance.