Gelcasting of ZTA/Cr2O3 ceramics for pressureless sintering of complex components: slurry rheological properties and mechanical properties

ZTA/Cr 2 O 3 ceramics were fabricated by gelcasting via gelcasting followed by pressureless sintering. The effects of pH, dispersant content, ball-milling time, solid loading, and Cr 2 O 3 content on slurry rheological properties, green body properties, sintering densification behavior, and mechanical properties were investigated. The addition of Cr 2 O 3 effectively decreased slurry viscosity and improves flowability, facilitating the preparation of high-solid-loading slurries. The green body relative density and flexural strength reached optimum values at a solid loading of 54 vol%, reaching 54.83% and 19.7 ± 0.27 MPa, respectively. After sintering at 1600 °C for 3 h, the optimum mechanical properties were obtained at a Cr 2 O 3 content of 0.4 vol%. The Vickers hardness, flexural strength, and fracture toughness were 17.17 ± 0.26 GPa, 581.22 ± 9.20 MPa, and 6.59 ± 0.32 MPa m 1/2 , respectively. Compared with Cr 2 O 3 -free ZTA ceramics, the hardness, flexural strength, and fracture toughness increased by 5.5%, 17.58%, and 10.75%, respectively. The enhanced mechanical properties are mainly attributed to the synergistic effects of the solid-solution incorporation of Cr 3+ in the α-Al 2 O 3 lattice, the resulting changes in lattice parameters, grain refinement, improved densification, and enhanced stability of the t-ZrO 2 phase. Furthermore, complex-shaped ZTA/Cr 2 O 3 ceramic components were successfully fabricated, showing no visible defects and uniform shrinkage after sintering, providing useful guidance for the near-net-shape fabrication of high-performance ceramic components.