Double layer ZrSi₂–ZrC–SiC/SiC oxidation protective coating for carbon/carbon composites

Abstract

A ZrSi₂–ZrC–SiC/SiC double layer coating was prepared on the surface of carbon/carbon (C/C) composites by pack cementation. The microstructure, oxidation and thermal shock resistance of the coating were studied. These results show that the outer coating is mainly composed of ZrSi₂, ZrC, SiC and Si respectively. Oxidation tests were conducted in air at 1173 K for 100 min and 1773 K for 67 h and a weight decrease of 0·37 and 0·12% were recorded. After 20 times thermal shocks between 1773 K and room temperature, the weight of the coated specimens increased by only 0·12%. The excellent thermal shock resistance is attributed to the aptness to oxidation of the minor phases distributing in the gaps among the SiC particles and the coarseness of the coating.

Keywords:

• Carbon/carbon composites
• Coating
• Oxidation
• Thermal shock