CVD and CVR Silicon-based functionally gradient coatings on CC composites

Carbon-carbon (CC) composites are considered an emerging technology critical to several military and commercial applications. However, CC composites' inherent susceptibility to air oxidation at temperatures above 500 °C greatly limits their use to primarily price-insensitive military and space applications. Over the past several decades huge R&D efforts were conducted to develop an effective oxidation protection system for CC composites. The acceptance of coating cracking was the basis of the majority of these efforts, resulting in an extensive and costly development of inhibitors and sealants. This paper addresses new and innovative approaches to the oxidation protection of CC composites based upon crackfree coatings produced by Chemical Vapor Deposition (CVD) and Chemical Vapor Reaction (CVR) technology. Correlation between coating properties and the oxidation behavior of the coated CC composites is discussed.