Ceramics and process for producing

Abstract

The present invention provides a process for producing alumina matrix carbide and boride reinforced ceramic composites wherein for any particular composite, the relative density is about 97% or more of the theoretical density. The composites are prepared in a container wherein the interior surfaces of the container are graphite and have a protective coating consisting of a first layer comprising silicon carbide and boron carbide with a binder and a second layer comprising silicon carbide particles, wherein the protective coating prevents carbon bleed-through and the protective coating maintains a boride-containing equilibrium atmosphere during the process. The present invention further provides an alumina-based ceramic composite which comprises a metal carbide preferably selected from the group consisting of silicon carbide, titanium carbide and zirconium carbide, and mixtures thereof, and a boride preferably selected from the group consisting of boron carbide, titanium boride, or zirconium boride, and mixtures thereof. Finally, the present invention provides a protective coating for a surface comprising a first layer of a silicon carbide and a boron carbide in a binder and a second layer comprising a silicon carbide wherein the protective coating is able to withstand repeated exposure to high temperature.