Additive manufacturing of zirconia parts by fused filament fabrication and solvent debinding: Selection of binder formulation

The material extrusion additive manufacturing technique known as fused filament fabrication (FFF) is an interesting method to fabricate complex ceramic parts whereby feedstocks containing thermoplastic binders and ceramic powders are printed and the resulting parts are subjected to debinding and sintering. A limiting factor of this process is the debinding step, usually done thermally. Long thermal cycles are required to avoid defects such as cracks and blisters caused by trapped pyrolysis products. The current study addresses this issue by developing a novel FFF binder formulation for the production of zirconia parts with an intermediate solvent debinding step. Different unfilled binder systems were evaluated considering the mechanical and rheological properties required for the FFF process together with the solvent debinding performance of the parts. Subsequently, the same compounds were used in feedstocks filled with 47 vol.% of zirconia powder, and the resulting morphology was studied. Finally, the most promising formulation, containing zirconia, styrene-ethylene/butylene-styrene copolymer, paraffin wax, stearic acid, and acrylic acid-grafted high density polyethylene was successfully processed by FFF. After solvent debinding, 55.4 wt.% of the binder was dissolved in cyclohexane, creating an interconnected porosity of 29 vol.% that allowed a successful thermal debinding and subsequent pre-sintering.