A thermal-initiated monomer binder enhancing green strength with low binder saturation for binder jetting additive manufacturing of cemented carbide

Abstract

Binder jetting (BJ) additive manufacturing (AM) technology is a competitive technology for fabricating ceramic and metal parts. In most cases, a high level of binder saturation is necessary to achieve sufficient strength for the green part. However, the oversaturated binder may lead to shape distortion and excess carbon residual of the green part. To solve the problem, a novel binder consisting of HEMA (2-Hydroxyethyl methacrylate) monomer and HDDA (1,6-Hexanediol diacrylate) monomer was proposed to improve the green strength and reduce carbon residual of parts at a low level of binder saturation. The monomer binder curing under the thermal-initiated free radical induced polymerization. This paper studies the printability, pyrolysis, and curing kinetics of the monomer binder, and investigates the effect of binder saturation on the strength and dimensional accuracy of WC-12Co green parts. The experimental results show that the monomer binder enables WC-12Co green parts to achieve a transverse rupture strength (TRS) of 0.66 MPa at a low binder saturation of 20%, and exhibits high dimensional accuracy. Additionally, the binder exhibited a high pyrolysis efficiency of 97.66%, resulting in a low residual carbon content of less than 0.3 wt% after debinding. This favorable pyrolysis characteristic does not compromise the phase composition of the WC-12Co matrix during the sintering process. This paper provides a new solution for fabricating cemented carbide parts with BJ AM technology.