Journal
CERAMICS INTERNATIONAL
Volume 46, Issue 13, Pages 21233-21242Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ceramint.2020.05.211
Keywords
Carbon-carbon composites; Coating; Hafnium carbide; Indentation; Mechanical behavior
Categories
Funding
- Korean government (Ministry of Trade, Industry and Energy, MOTIE) through Institute of Civil-Military Technology Cooperation
- Korean government (Defense Acquisition Program Administration, DAPA) through Institute of Civil-Military Technology Cooperation
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In this study, high-temperature oxidations and indentations on silicon carbide (SiC)- and hafnium carbide (HfC)-coated carbon-carbon (C/C) composites were investigated to prevent the oxidation of C/C composites in air. The SiC and HfC layers were coated to protect the composite from oxidizing in air at a high temperature. High-temperature oxidation tests were performed at 500 degrees C, 1,000 degrees C, 1,350 degrees C, and 1,500 degrees C for 1 h in air and then cooled to room temperature by thermal shock. This cycle was repeated until the coating layer was damaged. As a result of measuring the weight change according to the thermal cycle and observing the fiber damage in the C/C composites, the oxidation resistance of HfC was evaluated to be superior to that of SiC. The change of the mechanical behavior was investigated using an indentation test with a tungsten carbide ball with a radius of either 3.18 or 7.93 mm before and after the high-temperature oxidation WA by thermal shock. The relative elastic modulus was predicted based on the slope of the indentation load-displacement curve during loading or that of the curve during unloading. The relative hardness was also analyzed based on residual displacement after indentation. The hardness and elastic modulus of the HfC and SiC coating were higher than those of C/C composites and the mechanical properties of the HfC-coated C/C composite were relatively good compared with those of the SiC-coated composites prior to the thermal shock test. In particular, in this study, it was found that the mechanical behaviors of HfC-coated C/C composites exposed to temperatures > 1,000 degrees C in air were transferred from elastic to quasi-plastic. The quasi-plasticity of the HfC coating layer was evaluated to be excellent regarding its resistance to mechanical damage as the coating layer was not easily delaminated or damaged even by oxidation.
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