Effect of Al Powder on Property and Microstructure of Silica-based Ceramic Core

doi:10.15541/jim20180206

Abstract

Abstract:

Silica-based ceramic core was produced by fused silica as matrix material, corundum powder as mineralizer, and Al powder as additive. Effects of aluminum powder contents on the ceramic core regarding shrinkage rate, physical performance, and microstructure were investigated. Results showed that through sintering process, aluminum powder was oxidized to alumina, accompanying with volume expansion and weight gain, which reduced sintering and casting shrinkages of silica-based ceramic core. There is no obvious inhibitory effect on devitrification by Al powder in the sintering process. Due to increased looseness of core skeleton structure in the casting process, the high temperature creep deformation increased. The sample with 1wt% Al showed good comprehensive properties, of which three-dimensional direction of sintering shrinkage rate were 0.01%, 0.03%, 0.03%, respectively, and porosity rate, deflection bending strength were 28.58%, 0.57 mm, 12.1 MPa, respectively. All these data demonstrated that the new core materials can meet the requirement of directional solidification and be expected to improve the dimensional accuracy of the hollow turbine blade.

Key words: silica-based ceramic core, Al powder, sintering shrinkage, hollow blade

CLC Number:

TQ174

LI Xin, NIU Shu-Xin, YAO Jian-Sheng, TANG Ding-Zhong, CAO Chun-Xiao, YAN Jun-Hao. Effect of Al Powder on Property and Microstructure of Silica-based Ceramic Core[J]. Journal of Inorganic Materials, 2019, 34(2): 207-212.

Figures/Tables 11

Table 1 Characteristics of fused silica, alumina, and aluminite powder as raw materials

Raw materials	Purity/%	Particle size distribution/μm
Raw materials	Purity/%	D₁₀	D₅₀	D₉₀
Fused silica	≥99.95	7.5	34.4	104.0
Corundum	Al₂O₃≥99.5	3.2	15.9	40.5
Aluminite	≥99.5	-	1-3	-

Fig. 1 SEM images of Al powders(a) Room temperature; (b) 1100 ℃, 0.5 h

Fig. 2 Effect of Al content on sintering shrinkage of ceramic cores

Fig. 3 Thermal analysis graphs of Al powder

Fig. 4 Effect of Al content on as-casting shrikage of ceramic cores

Fig. 5 Flexural strength and apparent porosity results of the ceramic cores with various Al contents

Fig. 6 Variation of the creep deformation of ceramic core with Al contents

Fig. 7 Pore size distribution curve of as-casting ceramic core with different Al contents

Fig. 8 XRD patterns of Al powder heat-treatement at different temperatures

Fig. 9 XRD patterns of ceramic cores with different Al contents sintered at 1200 ℃

Fig. 10 SEM images of sintered core samples with various Al contents(a) 0; (b) 1wt%; (c) 3wt%; (d) 5wt%; (e) High magnification image of 3wt% sample; (f) High magnification image of 5wt% sample

References 17

[1]	GU GUO-HONG, CAO LA-MEI.Development of ceramic cores for investment casting hollow blades.Foundry Technology, 2002, 23(2): 81-83.
[2]	KANG HAI-FENG, LI FEI, ZHAO YAN-JIE,et al. Research status on ceramic cores and shells for superalloy hollow blades investment casting. Journal of Materials Engineering, 2013, 3(8): 85-91.
[3]	LI SHI-FENG, BU KUN, DONG YI-WEI,et al. Analyzing and controlling deformation of hollow turbine blade in near net-shape process. Proceedings of the Chinese Society for Electrical Engineering, 2011, 31(14): 109-112.
[4]	FENG WEI, WANG WEN-HU, WANG XIAO-ZHONG,et al. Size calculation method of ceramic core locators for hollow turbine blade investment casting wax patterns. Acta Aeronautica et Astronautica Sinica, 2013, 34(1): 181-186.
[5]	LI BO, SUN CHANG-BO, LIU YAN,et al. Effect of ceramic core powder particle size on inner cavity dimensions of casting. Foundry, 2015, 64(10): 1025-1028.
[6]	LIU XIAO-GUANG, LI XIN, TANG DING-ZHONG,et al. Effect of bimodal granularity distribution on the properties of silica-based ceramic cores. Materials Science Forum, 2017, 898: 1724-1731.
[7]	LI XIN, YAO JIAN-SHENG, LIU XIAO-GUANG,et al. Microstructure and performance of fused silica-based ceramic core reinforced by mullite fiber. Materials Science Forum, 2016, 848: 228-232.
[8]	LU Z L, FAN Y X, YANG D S,et al. The effect of SiC whisker on the performances of Al2O3 matrixceramics mould for hollow turbine blade. IEEE International Symposium on Assembly and Manufacturing, 2013: 85-87.
[9]	LIU XIAO-GUANG, QI CHANG-JIAN, HE LI-LI,et al. Effect of sintering temperature on ceramic cores performances of SiO2-ZrO2 system. Journal of Aeronautical Materials, 2011, 31(5): 62-65.
[10]	TRUNOV M A, UMBRAJKAR S M, SCHOENITZ M,et al. Oxidation and melting of aluminum nanopowders. Journal of Physical Chemistry B, 2006, 110(26): 13094.
[11]	SONG ZHEN-YA, WU YU-CHENG, YANG YE,et al. Preparation of alumina ultrafine powders and its modification by titania doping. Journal of the Chinese Ceramic Society, 2004, 32(8): 920-924.
[12]	CLAUSSEN N, JANSSEN R, HOLZ D.Reaction bonding of aluminum oxide (RBAO) science and technology.Journal of the Ceramic Society of Japan, 2010, 103(1200): 749-758.
[13]	TRUNOV M A, SCHOENITZ M, DREIZIN E L.Effect of polymorphic phase transformations in alumina layer on ignition of aluminium particles.Combustion Theory and Modelling, 2006, 10(4): 603-623.
[14]	CLAUSSEN N, LE T, WU S.Low-shrinkage reaction-bonded alumina.Journal of the European Ceramic Society, 1989, 5(1): 29-35.
[15]	ZHENG BIN, LIU JIA-CHEN, DU HAI-YAN,et al. Effect of boron nitride on crystallization of the quartz ceramic. Rare Metal Materials and Engineering, 2013, 42(S1): 370-372.
[16]	LIU JIN-QIU, PENG LI-HUA, QIN SHAN.Effect of Si3N4 on crystallinity of fused silica crucibles during casting.Refractories, 2016, 50(4): 248-251.
[17]	LI QIAN, MA DE-WEN, JIANG YIN-HONG,et al. Effect of cristobalite content on the properties of ceramic core in making directionally solidified hollow blade. Journal of Materials Engineers, 1994, 5: 18-19.