Fabrication of high-strength and anti-hydration water-soluble calcia-based ceramic core modified with nano-ZrO2 via direct ink writing method

Abstract

An additive manufacturing method, named direct ink writing (DIW), was adopted to fabricate high-strength and anti-hydration water-soluble calcia-based ceramic cores in this paper. The green bodies were prepared using calcium carbonate as precursor material, polyethylene glycol aqueous solution as binder and nano-ZrO2 as modifier, and then calcia-based ceramic cores were obtained by sintering at 1400 °C. The effect of different nano-ZrO2 contents on the properties and microstructure of the calcia-based ceramic cores was investigated. The results indicated that when the nano-ZrO2 content increased, the shrinkage rate of the ceramic cores in the X, Y and Z directions gradually decreased, the bending strength increased significantly and the hydration resistance enhanced, while the water-soluble rate decreased. The incorporation of nano-ZrO2 led to an augmentation in the CaZrO3 phase content within the CaO matrix of the calcia-based ceramic core. The CaZrO3 phase was interconnected and uniformly distributed around the CaO grain boundaries, which was the reason for increasing the bulk density of the ceramic core and increasing the sintering neck, reducing linear shrinkage rate and improving bending strength, while decreasing the water-soluble rate. The high-strength and anti-hydration water-soluble calcia-based ceramic core is achieved by adding 10 wt% nano-ZrO2, with the bending strength of 11.68 MPa, the shrinkage rate of 16.72%, 48h moisture absorption rate of 5.88%, and the water-soluble rate of 4.21 g/(s·m2) in 60 °C water, which is suitable for the rapid casting of the complex internal castings.