| abstract |
In accordance with the invention, compositions of matter are provided for forming two coatings for protecting carbonaceous substrates from degradation at elevated temperatures and to improve said substrate's resistance to surface crazing and cracking. Preferably, the compositions are a mixture of particulate silicon, silicon carbide, alumina and boron. Preferably, the primary mixture contains between about 40% and 50% silicon by weight of the total composition, between about 30% and 50% silicon carbide by weight of the total composition, and between about 20% and 30% alumina by weight of the total composition. Preferably, the secondary mixture contains between about 25% and 40% silicon by weight of the total composition, between about 50% and 70% silicon carbide by weight of the total composition, between about 1% and 15% boron by weight of the total composition, and a minor amount of magnesium oxide. The method is provided for forming a primary protective coating on carbonaceous substrates utilizing the aforesaid primary and secondary mixtures. |