Influence of Oxidation Behavior of Feedstock on Microstructure and Ablation Resistance of Plasma-Sprayed Zirconium Carbi
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JTTEE5 24:1302–1311 DOI: 10.1007/s11666-015-0307-2 1059-9630/$19.00 ASM International
Influence of Oxidation Behavior of Feedstock on Microstructure and Ablation Resistance of Plasma-Sprayed Zirconium Carbide Coating Cui Hu, Xuelian Ge, Yaran Niu, Hong Li, Liping Huang, Xuebin Zheng, and Jinliang Sun (Submitted March 19, 2015; in revised form August 10, 2015) Plasma spray is one of the suitable technologies to deposit carbide coatings with high melting point, such as ZrC. However, in the spray processes performed under atmosphere, oxidation of the carbide powder is inevitable. To investigate the influence of the oxidation behavior of feedstock on microstructure and ablation resistance of the deposited coating, ZrC coatings were prepared by atmospheric and vacuum plasma spray (APS and VPS) technologies, respectively. SiC-coated graphite was applied as the substrate. The obtained results showed that the oxidation of ZrC powder in APS process resulted in the formation of ZrO and Zr2O phases. Pores and cracks were more likely to be formed in the as-sprayed APS-ZrC coating. The VPS-ZrC coating without oxides possessed denser microstructure, higher thermal diffusivity, and lower coefficients of thermal expansion as compared with the APS-ZrC coating. A dense ZrO2 layer would be formed on the surface of the VPS-ZrC-coated sample during the ablation process and the substrate can be protected sufficiently after being ablated in high temperature plasma jet. However, the ZrO2 layer, formed by oxidation of the APS-ZrC coating having loose structure, was easy to be washed away by the shearing action of the plasma jet.
Keywords
ablation resistance, atmospheric plasma spray, oxidation behavior, vacuum plasma spray, ZrC coating
1. Introduction Carbon materials, such as graphite and carbon/carbon composites (C/C composites), are ideal structural materials applied in ultra-high temperature environments due to their low density, excellent mechanical properties and thermal shock resistance, et al. Nevertheless, carbon materials could be oxidized in an oxidizing environment and thus their applications are limited (Ref 1, 2). Applying an external coating is a promising method to offer protection for carbon materials. Zirconium carbide (ZrC), as one of the ultra-high temperature ceramics, possessing desirable comprehensive properties of high melting point Cui Hu, Yaran Niu, Liping Huang, and Xuebin Zheng, Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China; Xuelian Ge, Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China and Research Center of Composite Materials, Shanghai University, Shanghai 200072, China; and Hong Li and Jinliang Sun, Research Center of Composite Materials, Shanghai University, Shanghai 200072, China. Contact e-mails: [email protected] and xbzheng@ mail.sic.ac.cn
1302—Volume 24(7) October 2015
(3420 C), high thermal conductivity, and good ablation resis
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