Cyclic Ablation Behaviors of ZrB2–SiC Composites Sintered with Nano‐Sized Particles

• Published in: Advanced engineering materials 2018-11, Vol.20 (11), p.n/a
• Main Authors: Li, Pan, Jin, Xiaochao, Hou, Cheng, Wang, Xiaobing, Yuan, Meini, Fan, Xueling
• Format: Article
• Language: English
• Subjects: ablation test; oxidation reaction; spark plasma sintering; ultra‐high temperature ceramic
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201800551

Ultra‐high temperature ceramic (UHTC) is one of the most promising materials used in thermal protection system for hypersonic flight vehicles. In this work, ZrB2–0.5 vol% SiC composites are fabricated with nano‐sized ZrB2 and SiC particles by spark plasma sintering (SPS) at 1500 °C. The average density of the composites reaches 5.47 g cm−3, while the average grain size is only 1 μm. Then, single and cyclic ablation tests are conducted using a plasma generator. Ablation mechanisms and microstructure evaluation of the composites are discussed in detail. In addition, a digital optical microscope system is adopted to obtain the surface micrograph after ablation. Results show that ablation center will become protuberant rather than form an ablation crater, due to the relative porous and loose oxide layer and flushing action of ablation flame. Thickness of oxide layer and mass gain of the sample obviously increase during the single ablation, while the mass change rate decreases gradually and is then kept stable with the ablation time increasing. Compared with the single ablation, the cyclic ablation leads to higher mass gain and mass change rate, as many microcracks formed on the surface which will significantly accelerate the oxidation. ZrB2 based ultra‐high temperature ceramic is one of the most promising materials for thermal protection system applications, due to the high melting points and excellent mechanical properties. In this work, single and cyclic ablations under plasma jet are performed to provide a better understanding of the ablation mechanisms of ZrB2 based ceramics.