Hafnium Carbide Coatings Deposited by Suspension Vacuum Plasma Spraying for Ultra-High-Temperature Oxidation Barrier on Carbon Composites

Hafnium carbide (HfC) coatings on carbon composites have been extensively researched owing to their excellent high-temperature properties. However, it is still challenging to fabricate thick coatings. Vacuum plasma spraying is one of the methods of fabricating thick coatings. However, the formation of dense coatings is a problem because conventional sized thermal spray powders possessing ultra-high melting temperatures cannot be satisfactorily melted. In this study, a dense 50-mu m-thick HfC coating was fabricated via suspension vacuum plasma spraying using nanometer-sized powders. The HfC coating was characterized through scanning electron microscopy and X-ray diffraction. The HfC coating contained hafnium oxide owing to the reaction with the oxygen present in the solvent during the spraying process. The ultra-high-temperature oxidation resistance of the HfC coating was determined by performing a laser oxidation test at 2000 degrees C. The weight reduction rate of HfC-coated carbon composites was seven times less than that of uncoated carbon composites.