Surface-engineered bimodal yttria powder system enables high-performance ceramic cores via binder jetting for titanium alloy casting

This study employs a bimodal powder system composed of nanoscale agglomerated spherical particles and micrometer-scale irregular particles to fabricate yttria (Y 2 O 3 ) ceramic cores via Binder Jetting (BJ) technology, aiming to overcome sintering challenges in titanium alloy casting. This study employs an innovative two-step surface modification method for spherical powders: first, coating with 4wt% bis (dioctyl pyrophosphate) vinyl titanate to suppress binder adsorption, followed by activation with 3wt% fatty alcohol polyoxyethylene ether to enhance wettability, ultimately achieving a BJ forming process based on nanopowders. The optimized bimodal mixing ratio (fine powder 24.5%/coarse powder 75.5%) endows the powder bed with exceptional packing density (2.143 g/cm 3 ) and flowability (Hausner ratio=1.41), while the formed green body exhibits excellent bulk density (2.10 ± 0.13 g/cm 3 ) and flexural strength (2.56±0.108 MPa). After sintering at 1700°C, the F24.5C75.5 formulation exhibited accurate anisotropic shrinkage (X-axis: 8.67±0.44%, Y-axis: 9.24±0.46%, Z-axis: 11.64±0.74%), achieving a flexural strength of 23.86±1.2 MPa—a 166% improvement compared to the pure micron-scale formulation—along with a surface roughness of 8.96±0.47 μm, meeting aerospace standard SAE AS71051. Mechanistic analysis revealed that nanoclusters promote interparticle neck formation, while micron-scale particles provided a dimensional anchoring effect, establishing a new paradigm for refractory ceramic additive manufacturing.