Process of producing a ceramic matrix composite article and article formed thereby
A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.
1. A ceramic matrix composite article comprising:
a ceramic matrix composite substrate comprising silicon carbide and containing a ceramic reinforcement material in a ceramic matrix material, a fraction of the reinforcement material being at a surface of the substrate, wherein at least a portion of the ceramic reinforcement material is coated with interface layers comprising boron nitride and carbon and wherein an outermost interface layer is coated with at least one coating layer comprising silicon carbide or silicon nitride; and
a ceramic protective layer on the ceramic matrix composite substrate defining an outermost surface of the ceramic matrix composite article, wherein the ceramic protective layer comprises carbon-containing filamentary material and does not comprise the reinforcement material of the ceramic matrix composite substrate.
2. The ceramic matrix composite article according to claim 1 , wherein the ceramic protective layer comprises the ceramic matrix material.
3. The ceramic matrix composite article according to claim 1 , further comprising an environmental barrier coating on the ceramic protective layer.
4. The ceramic matrix composite article according to claim 1 , wherein the ceramic protective layer is harder than the ceramic matrix composite substrate.
5. The ceramic matrix composite article according to claim 1 , wherein the filamentary material comprises carbon, silicon carbide, a polymer, or combinations thereof.
6. The ceramic matrix composite article according to claim 5 , wherein the filamentary material comprises chopped or milled fibers.
7. The ceramic matrix composite article according to claim 5 , wherein the filamentary material comprises carbon paper or mat.
8. The ceramic matrix composite article according to claim 7 , wherein the filamentary material comprises a carbon mat.
9. The ceramic matrix composite article according to claim 8 , wherein the carbon mat comprises a low density, non-directional carbon paper.
10. The ceramic matrix composite article according to claim 1 , wherein the ceramic reinforcement material comprises silicon carbide fibers.