An in-situ crosslinking binder for binder jet additive manufacturing

Abstract

Additive Manufacturing (AM) of metals is a potentially disruptive technology that could significantly change the industrial supply chain. There are a limited number of AM methods capable of creating metal parts, and one method showing significant potential is Binder Jet AM (Binder Jetting). Binder Jetting utilizes an inkjet print head to deposit a binder fluid onto a powder bed and bind together powder particles into a desired geometry. This study investigates a new binder system consisting of a difunctional monomer, triethylene glycol dimethacrylate (TEG-DMA). TEG-DMA exhibits excellent printability with an Ohnesorge’s number of .258 making the Z number 3.876. During the thermal curing process, the difunctional monomer polymerizes and crosslinks at the onset temperature of 138 °C, becoming a solid dimethacrylate network. When the binder is utilized within the stainless-steel powder bed at 200 °C, it forms a network incorporating the stainless-steel particles, binding the powder into any specified geometry. Crosslinking the monomer within the stainless-steel 420 powder bed imparts a flexural strength of 1.0–3.3 MPa to the green part depending on the volume of monomer in the part. After sintering, the final stainless-steel parts results in a void fraction close to 60 % and carbon content below 0.4 %.