Microstructure and properties of 3D-printed alumina ceramics with different heating rates in vacuum debinding

The effect of heating rates during vacuum debinding on the microstructure and mechanical properties of alumina ceramics are discussed in this paper. The three-dimensional (3D)-printed alumina ceramics examined in this study were found to have a layered structure, and interlayer spacing increased as the heating rate increased. The pore diameter, shrinkage, flexural strength and hardness were found to decrease as the heating rate increased due to weak interfacial bonding between alumina particles. Shrinkage was found to be much larger along the Z direction than along the X or Y directions due to the layer-by-layer forming mode during 3D printing. 0.5 °C·min⁻¹ is considered the optimum heating rate, yielding ceramics with interlayer spacing of 0.65 µm, shrinkage of 2.6%, 2.3% and 4.0% along the X, Y and Z directions, respectively, flexural strength of 27.5 MPa, hardness of 29.8 GPa, Vickers hardness of HV 266.5, pore diameter of 356.8 nm, bulk density of 2.5 g·cm⁻³, and open porosity of 38.4%. The debinding procedure used in this study could be used to produce a high-quality ceramic which can be used for fabricating alumina ceramic cores.