Effects of Powder Particle Size on Fatigue Performance of Laser Powder-Bed Fused Ti-6Al-4V

Abstract

In powder-based metal additive manufacturing, one key specification that needs to be precisely optimized is the particle shape and size distribution of metallic powders. Particle shape and size distribution influences the flowability of the powder and the uniformity of powder bed density (i.e. packing state of the powder). These eventually affect the porosity, which ultimately influences the fatigue performance of the fabricated parts. Therefore, it is essential to understand the effect of powder characteristics on the fatigue behavior before additively manufactured parts can be used in load-bearing, safety-critical applications. The current study aims at assessing the effects of powder particle size and morphology on mechanical properties and fatigue response of laser beam powder bed fused (LB-PBF) Ti-6Al-4V; an alpha-beta workhorse alloy of the titanium family. Several Ti-6Al-4V powder batches with different size distributions are used to fabricate the parts employing an EOS M290 machine. Powder characteristics, including flowability, compressibility, cohesion, size, and shape morphology, are investigated to reveal the differences between the two tested powder batches. Porosity levels and mechanical testing results are compared among specimens fabricated from different powder batches and the differences are explained based on variations in powder characteristics.