Reactive binder jet additive manufacturing for microstructural control and dimensional stability of ceramic materials

Abstract

Binder jet additive manufacturing (BJAM) is particularly suited to processing brittle materials such as ceramics as its process flow separates the steps of shaping and densification. Polymer binders are typically used in BJAM, including for the processing of ceramics. However, ceramic components in the green state are especially prone to distortion or fracture during sintering due to the low strength of polymer-bound parts after polymer decomposition and high sintering temperatures of ceramics. This paper presents the development and use of reactive metal salt binders for BJAM of ceramic components. Using aluminum oxide as the feedstock powder, we compare the performance of aluminum nitrate and magnesium nitrate metal salts as binders, and polyethylene glycol as a reference polymer binder. Test components are fabricated using a custom BJAM testbed, sintered, and characterized for density and deformation. The metal salt binders form solid interparticle bridges after decomposition, which provide continued strength to printed components during sintering. Additionally, increased densification results from the use of magnesium nitrate binders and reduced shrinkage results from use of aluminum nitrate binders, showcasing the utility of reactive binders that convert into ceramic sintering aids upon decomposition and sustain part strength during sintering. • A custom binder jet additive manufacturing testbed is used to fabricate ceramic components with reactive metal salt binders. • Reactive metal salt binders form solid metal oxide bridges between powder particles upon post-print decomposition. • Reactive binders provide continued part strength during sintering with reduced deformation compared to polymer binder. • Sintered density of printed components is increased through the use of magnesium nitrate reactive metal salt binders. • Part shrinkage of printed components is reduced through the use of aluminum nitrate reactive metal salt binders.