Effect of Particle Size Distribution on Powder Packing and Sintering in Binder Jetting Additive Manufacturing of Metals

Abstract

The binder jetting additive manufacturing (AM) process provides an economical and scalable means of fabricating complex parts from a wide variety of materials. While it is often used to fabricate metal parts, it is typically challenging to fabricate full density parts without large degree of sintering shrinkage. This can be attributed to the inherently low green density and the constraint on powder particle size imposed by challenges in recoating fine powders. To address this issue, the authors explored the use of bimodal powder mixtures in the context of binder jetting of copper. A variety of bimodal powder mixtures of various particle diameters and mixing ratios were printed and sintered to study the impact of bimodal mixtures on the parts' density and shrinkage. It was discovered that, compared to parts printed with monosized fine powders, the use of bimodal powder mixtures improves the powder's packing density (8.2%) and flowability (10.5%), and increases the sintered density (4.0%) while also reducing the sintering shrinkage (6.4%).

Binder jetting additive manufacturing process fundamentals and the resultant influences on part quality.

“…Therefore, it can be concluded that the quality of the final parts produced by BJ-AM technology is determined not only by the parameters related to green part fabrication process but also by the post-printing processes and affecting factors [14]. There exist multiple factors that could potentially influence the feature resolution and quality of the green components fabricated via BJ-AM process such as binder and powder physical properties, powder bed characteristics, droplet impact velocity, and powder material wettability to the liquid binder [13,95,155,157,158]. One of the key parameters in determining the minimum feature size and final part quality in BJ-AM process is the interactions between the liquid binder droplets and the powder materials.…”

“…The effect of particle size distribution on the surface finish of additively manufactured parts has been demonstrated by different researchers in the literature [157,163]. Generally, smaller particles result in improved surface quality of components due to the diminished staircase effect, as well as the use of thinner layers [157,164].…”

The Influence of Printing Parameters, Post-Processing, and Testing Conditions on the Properties of Binder Jetting Additive Manufactured Functional Ceramics

“…Particle size distribution was demonstrated to have a considerable impact on the green body density of 3D-printed materials [21,25]. Multimodal particle size was shown to increase the density of BJT-printed ceramic and metallic parts.…”

Beamless Metal Additive Manufacturing

“…The main limitation of metal binder jetting is the relative density of metal parts (95-97%), which can be compared with a typical density of > 99% with laser-based powder bed systems. A number of research works have been conducted to investigate the effect of process parameters (such as layer thickness, binder saturation, drying after printing each layer) and part orientation [58,71], powder particle size and distribution [53,[72][73][74], and post-processing [47] on density, and mechanical properties. The influence of layer thickness, powder particle size and sintering profiles in the binder jetting of IN718 superalloy was studies by Turker et al [58].…”