Abstract
In this work, alumina ceramics were formed via stereolithography based 3D printing technology. Effects of holding time during sintering on microstructure and properties of alumina ceramics were investigated. Sintered alumina ceramics were made up of layered structures due to layer-by-layer forming method. In addition, interlayer spacing decreased with the increase in holding time. Average particle size, shrinkage, crystallite size, flexural strength, and hardness increased with the increase in holding time due to strong interfacial bonding among alumina particles. Open porosity decreased slightly as holding time increased. Moreover, it was found that holding time had little influence on bulk density, phase composition, and chemical bonds of the ceramic. The shrinkage in Z direction was about 1.8 times higher than that in X or Y direction due to layered structure caused by 3D printing forming method. The optimum holding time was 90 minutes, which resulted in ceramic product with interlayering spacing of 11.8 μm, shrinkage of 2.1% in X direction, 2.1% in Y direction, and 4.1% in Z direction, flexural strength of 20.7 MPa, hardness of 17.6 GPa, Vickers hardness of 114.3 HV, bulk density of 2.5 g/cm3, and open porosity of 39.0%.
Highlights
Alumina ceramic core is a complex part with fine structure, which can be used to manufacture high-temperature hollow turbine blades because it provides efficient cooling passage for the blades (Gromada et al, 2015)
No cracks were found in the samples when the holding time during sintering was increased to 60 min or longer
Photosensitive resin was heated and turned into gases, such as carbon dioxide and water vapor. These volatile components were removed from the green bodies, and only alumina powder was left in the samples after the debinding process (Choi and Jeong, 2009), the sintering process was conducted to promote the alumina particles to stick together
Summary
Alumina ceramic core is a complex part with fine structure, which can be used to manufacture high-temperature hollow turbine blades because it provides efficient cooling passage for the blades (Gromada et al, 2015). Alumina ceramic has excellent properties, such as low thermal expansion coefficient, high chemical stability, and good high-temperature performance (Ikeda et al, 2011). It is extensively applied in the astronautics engineering and material engineering fields related to high-temperature environments (Chen et al, 2019). One of the most difficult and significant problems of preparing alumina ceramic core is its preparation method and prototyping precision.
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