| Crack healing in the SiC–SiC ceramic matrix composites fabricated with different process |
| Zicheng Meng1, Tae Woo Kim1, Sung Min Lee2, Kee Sung Lee1 |
1School of Mechanical Engineering, Kookmin University, Seoul 02707, Korea
2Engineering Ceramics Team, Korea Institute of Ceramic Engineering Technology (KICET), Icheon 17303, South Korea |
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Received: March 27, 2020; Revised: May 29, 2020 Accepted: August 10, 2020. Published online: January 31, 2021. |
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| ABSTRACT |
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In this study, crack healing in a SiC–SiC ceramic matrix composite (CMC) was investigated. As a gas turbine often operates at a high temperature above 1350 °C and is frequently cooled to room temperature, small cracks that form in the interior of a hot gas component propagate to the surface of the component. Owing to a mechanical constraint condition and dynamic vibrations, stress concentration occurs at the cracks, which grow and eventually reduce the service life of the turbine component. Self-healing technology has been used to solve this problem. We studied the crack-healing behavior of plate-type SiC–SiC CMC samples prepared by liquid melt infiltration (LMI) and cylindrical SiC–SiC CMC samples produced by chemical vapor infiltration (CVI) in an experiment. First, a crack was deliberately formed on the surface of the samples through indentation. Subsequently, the sample was subjected to heat treatment, in which the crack-healing temperature and the healing time were controlled. The crack-healing regions on the surface of the samples were observed using a scanning electron microscope, and the composition of the crack-healing region was analyzed by energy-dispersive spectrometry. While the cracks in the SiC–SiC CMC samples prepared by CVI were healed at 1500 °C, those in the SiC–SiC CMC samples produced by LMI were healed at a lower temperature, 1400 °C, because of the oxidation of residual Si. The four-point bending test was performed at room temperature and a high temperature (1200 °C) on the SiC–SiC CMC samples prepared by LMI, and it confirmed the healing in the samples. |
| Key words:
Coatings · Crack healing · Strength · Indentation |
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