Infiltration of Nanoparticles into Porous Binder Jet Printed Parts

Abstract

The densification of parts that are produced by binder jetting Additive Manufacturing (AM; a.k.a. “3D Printing”) is an essential step in making them mechanically useful. Increasing the packing factor of the powder bed by incorporating nanoparticles into the binder has potential to alleviate the amount of shrinkage needed for full densification of binder jet parts. In this study we present preliminary data on the use of 316L Stainless Steel Nanoparticles (SSN) to densify 316L stainless steel binder jet parts. Aqueous solutions of Diethylene Glycol (DEG) or Ethylene Glycol (EG) were prepared at different DEG/water and EG/water molar ratios; pH of the solutions was adjusted by the use of 0.10 M sodium hydroxide. Nanoparticles were suspended in a resulted solution at a volume percentage of SSN/solution at 0.5%. The suspension was then sonicated for thirty minutes. One milliliter of the suspension was added stepwise to a sintered, printed disk with the dimensions: (d = 10 mm, h = 3 mm) in the presence of a small magnet. The 3D part was then sintered again. The increase in the mass of the 3D part was used as indication of the amount of nanoparticles that diffused in the 3D part. This mass percent increase was studied as a function of pH of the suspension and as function DEG/water molar ratio. Unlike EG, data show that change in pH affects the mass percent when the suspension was made with DEG. Optical analysis of the discs’ cross sections revealed trends metallic densities similar to trends in the data for mass increase with changing pH and water molar ratio.