Ultra-High-Temperature Ceramic Coatings ZrC, ZrB2, HfC, and HfB2

Ultra-high-temperature ceramic coatings are a fast-developing field of study with a broad variety of applications. Due to their exceptional physical and chemical characteristics, like heat resistance, oxidation resistance, and thermal stability zirconium and hafnium-based carbide and boride coatings have gained considerable popularity. Refractory carbide coatings of zirconium and hafnium are mostly used in ultra-high-temperature applications. Zirconium carbide possesses both ceramic and metallic properties, such as a very high melting point, high hardness, and exceptional corrosion resistance. Zirconium carbide coatings are also good hydrophobic and have low interfacial contact resistance. Because of these unique qualities, hafnium carbide has a very high melting point of 3890 ℃ and is also chemically stable at high temperatures. Hafnium carbide forms a protective oxide layer of HfO2 on top of it to protect the substrate against oxidation at ultra-high temperatures. HfO2 also has a very high melting point which further protects the underlying coating and substrate. These characteristics make hafnium carbide very promising as an anti-ablation coating for ultra-high-temperature applications. The deposition of zirconium boride (ZrB2) and hafnium boride (HfB2) provides the substrate with thermal and mechanical protection. Mechanical and physical properties of the composites are studied to determine optimal conditions for the application of such coatings.