Preparation and Ablation Properties of Y 2 SiO 5 Coating for SiC-Coated C/C Composites by Supersonic Plasma Spraying
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JTTEE5 24:994–1001 DOI: 10.1007/s11666-015-0256-9 1059-9630/$19.00 Ó ASM International
Preparation and Ablation Properties of Y2SiO5 Coating for SiC-Coated C/C Composites by Supersonic Plasma Spraying Jia-Ping Zhang, Qian-Gang Fu, Lei Zhuang, He-Jun Li, and Can Sun (Submitted November 19, 2014; in revised form May 19, 2015) Y2SiO5 coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying at different powers of 35, 40, 45, and 50 kW. The microstructures and phase compositions were characterized by scanning electron microscopy and x-ray diffraction, respectively. Roughness of the coating was measured by a confocal laser scanning microscope. Bonding force between Y2SiO5 outer coating and SiC inner coating was measured by a scratch tester. The results show that Y2SiO5 coating prepared at the spraying power of 45 kW possesses the biggest deposition rate, minimum surface roughness (Ra = 11.12 lm), and maximum bonding force (up to 28 N). The linear and mass ablation rates of Y2SiO5 coating prepared at 45 kW are 2.6 lm/s and 0.031 mg cm22 s21 in the heat flux of 2.38 MW/m2 under oxyacetylene torch. During ablation, a glassy layer of SiO2 + Y2O3 was formed, acting as a barrier to high-speed gas flow of oxyacetylene flame.
Keywords
bond strength, ceramics, corrosion resistance, plasma spray forming
1. Introduction Carbon/carbon (C/C) composites, having high strengthto-weight ratio and retention of mechanical properties, are extensively applied as thermo-structural materials for aerospace vehicles (Ref 1). Unfortunately, poor ablation resistance of C/C composites is the key factor that restricts the more comprehensive applications (Ref 2, 3). Coating technology has been proved to be an effective method for improving the ablation resistance of C/C composites (Ref 4, 5). Up to date, many multilayer ceramic coatings, such as SiC/ Zr-Si-C (Ref 6), SiC/ZrB2-SiC (Ref 7), and AlPO4-SiCMoSi2/SiC (Ref 8), have been developed. Due to its good physical and chemical adaptability with C/C composites, SiC coating was usually selected as an internal buffer layer in multilayer coating systems (Ref 6–9). However, the mismatch of thermal expansion coefficient (CTE) between ceramic outer coating and SiC inner coating might result in an inevitable damage of the coating when exposed in high-speed gas flow. Y2SiO5 (Ref 10), having a similar CTE with that of SiC (aY2SiO5 = 4.8 9 106 K1 (Ref 10), aSiC = 4.5 9 106 K1 (Ref 11), possesses low evaporation rate, low oxygen permeability, and good damage tolerance that might effiJia-Ping Zhang, Qian-Gang Fu, Lei Zhuang, He-Jun Li, and Can Sun, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, XiÕan 710072, P.R. China. Contact e-mails: [email protected] and fuqiangang@ nwpu.edu.cn.
994—Volume 24(6) August 2015
ciently address the problem of CTE mismatch. Extensive studies have been conducted on the fabrication of Y2SiO5 coating, such as dip coating (Ref 12) and electrophoretic deposition (Ref 13). In order to
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