Abstract
Urchin-like mullite whiskers synthesized by the vapor–liquid–solid growth method were used to improve the high-temperature performance of porous gelcast SiO2-based ceramic molds. Aluminum was used to facilitate the synthesis of polycrystal urchin-like mullite whiskers which acted as bridges between particles. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the microstructures and phase compositions of the sintered ceramic samples, respectively. Urchin-like mullite whiskers with diameters of 0.2~1.0 µm and lengths of 1.0~8.0 µm were successfully synthesized in SiO2-based ceramic. When 15 vol% Al was added, the high-temperature strength at 1200 °C was improved from 8.5 to 27.5 MPa, and the creep deformation was decreased to 0.56 mm. Meanwhile, a sintering shrinkage below 0.3% was obtained, and the de-coring rate was accelerated by 67% compared to that of the pure SiO2-based ceramic. This method showed excellent high-temperature strength and high precision, having remarkable potential in the fabrication of hollow turbine blades.
Highlights
SiO2 -based ceramic molds are widely used for casting hollow turbine blades for gas turbines and aircraft engines [1] because of their low density, good leachability, and excellent creep resistance [2,3,4].Li put forward the integral fabrication technique (IFT) to manufacture ceramic molds with complex internal cores by stereolithography (SL) and gelcasting methods [5]
2-based ceramic mold, indicating that urchin-like mullite whiskers synthesized through the VLS growth method were effective in improving the high-temperature synthesized through the VLS growth method were effective in improving the high-temperature performance of porous SiO2 -based ceramic molds which meet the requirements of investment casting performance ofxporous
The high-temperature performance of SiO2-based ceramic molds was significantly improved by the use of urchin-like mullite whiskers synthesized using the VLS growth method
Summary
SiO2 -based ceramic molds are widely used for casting hollow turbine blades for gas turbines and aircraft engines [1] because of their low density, good leachability, and excellent creep resistance [2,3,4]. Many methods, including mineralizer addition [8], high solid loading [4], infiltration strengthening [9], as well as fiber or whisker addition [10,11,12], have been used to improve the high-temperature strength of SiO2 -based ceramic molds in much research. Few reports about the high-temperature strength of gelcast SiO2 -based ceramic molds reinforced by VLS synthesized mullite whiskers have appeared in the literature. The oxidation of Al proceeds as both solid/gas and liquid/gas reactions which could provide the VLS growth conditions [24] It can be considered a sintering additive to facilitate the formation of mullite in SiO2 -based ceramic. SiO2 -based ceramic molds were investigated, and the strengthening mechanism of high-temperature strength was discussed
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