The disclosure describes a method for forming a surface layer of a ceramic matrix composite (CMC) article. The technique includes depositing a slurry on a surface of an infiltrated CMC. The slurry includes a carrier material, a binder, a plasticizer, and solid particles. The solid particles include a plurality of fine ceramic particles defining a fine particle average size less than about 5 micrometers. The method further includes drying the slurry to form an article having an outer surface layer that includes the solid particles on the infiltrated CMC. The method further includes machining at least a portion of the outer surface layer of the article. The method further includes infiltrating the article with a molten infiltrant to form a composite article.

The disclosure describes a method for forming a surface layer of a ceramic matrix composite (CMC) article. The technique includes depositing a slurry on a surface of an infiltrated CMC. The slurry includes a carrier material, a binder, a plasticizer, and solid particles. The solid particles include a plurality of fine ceramic particles defining a fine particle average size less than about 5 micrometers. The method further includes drying the slurry to form an article having an outer surface layer that includes the solid particles on the infiltrated CMC. The method further includes machining at least a portion of the outer surface layer of the article. The method further includes infiltrating the article with a molten infiltrant to form a composite article.

The disclosure describes techniques for forming a surface layer of an article including a CMC using a cast. In some examples, the surface layer includes three-dimensional surface features, which may increase adhesion between the CMC and a coating on the CMC. In some examples, the surface layer may include excess material, with or without three-dimensional surface features, which is on the CMC. The excess material may be machined to remove some of the excess material and facilitate conforming the article to dimensional tolerances, e.g., for fitting the article to another component. The excess material may reduce a likelihood that the CMC (e.g., reinforcement material in the CMC) is damaged by the machining.

The disclosure describes techniques for forming a surface layer of an article including a CMC using a cast. In some examples, the surface layer includes three-dimensional surface features, which may increase adhesion between the CMC and a coating on the CMC. In some examples, the surface layer may include excess material, with or without three-dimensional surface features, which is on the CMC. The excess material may be machined to remove some of the excess material and facilitate conforming the article to dimensional tolerances, e.g., for fitting the article to another component. The excess material may reduce a likelihood that the CMC (e.g., reinforcement material in the CMC) is damaged by the machining.

Methods for producing components for use in high temperature systems that include reacting a fluid reactant and a porous preform that has a pore volume and contains a solid oxide reactant that defines a solid volume of the porous preform. The method includes infiltrating the fluid reactant into the porous preform to react with the solid oxide reactant to produce a oxide/metal composite component, during which a displacing metal replaces a displaceable species of the solid oxide reactant to produce at least one solid oxide reaction product that has a reaction product volume that at least partially fills the pore volume. The oxide/metal composite component includes at least one oxide phase and at least one metal phase. The component is exposed to temperatures greater than 500° C. and the at least one oxide phase and the at least one metal phase exhibit thermal expansion values within 50% of one another.

Methods for producing components for use in high temperature systems that include reacting a fluid reactant and a porous preform that has a pore volume and contains a solid oxide reactant that defines a solid volume of the porous preform. The method includes infiltrating the fluid reactant into the porous preform to react with the solid oxide reactant to produce a oxide/metal composite component, during which a displacing metal replaces a displaceable species of the solid oxide reactant to produce at least one solid oxide reaction product that has a reaction product volume that at least partially fills the pore volume. The oxide/metal composite component includes at least one oxide phase and at least one metal phase. The component is exposed to temperatures greater than 500° C. and the at least one oxide phase and the at least one metal phase exhibit thermal expansion values within 50% of one another.

A method to form a machinable ceramic matrix composite comprises forming a porous ceramic multilayer on a surface of a fiber preform. In one example, the porous ceramic multilayer comprises a gradient in porosity in a direction normal to the surface. In another example, the porous ceramic multilayer includes low-wettability particles having a high contact angle with molten silicon, where an amount of the low-wettability particles in the porous ceramic multilayer varies in a direction normal to the surface. After forming the porous ceramic multilayer, the fiber preform is infiltrated with a melt, and the melt is cooled to form a ceramic matrix composite with a surface coating thereon. An outer portion of the surface coating is more readily machinable than an inner portion of the surface coating. The outer portion of the surface coating is machined to form a ceramic matrix composite having a machined surface with a predetermined surface finish and/or dimensional tolerance.

A method to form a machinable ceramic matrix composite comprises forming a porous ceramic multilayer on a surface of a fiber preform. In one example, the porous ceramic multilayer comprises a gradient in porosity in a direction normal to the surface. In another example, the porous ceramic multilayer includes low-wettability particles having a high contact angle with molten silicon, where an amount of the low-wettability particles in the porous ceramic multilayer varies in a direction normal to the surface. After forming the porous ceramic multilayer, the fiber preform is infiltrated with a melt, and the melt is cooled to form a ceramic matrix composite with a surface coating thereon. An outer portion of the surface coating is more readily machinable than an inner portion of the surface coating. The outer portion of the surface coating is machined to form a ceramic matrix composite having a machined surface with a predetermined surface finish and/or dimensional tolerance.

In a method of making a gaseous emissions treatment component, a ‘green’ ceramic mix is extruded through a die to form an extrusion having cells extending along the extrusion, the cells being bounded by walls dividing adjacent cells from one another. In concert with the extruding, metal is fed through the die with the extruded mix. A length of the extrusion and associated metal is then cut off and fired to form the component.

In a method of making a gaseous emissions treatment component, a ‘green’ ceramic mix is extruded through a die to form an extrusion having cells extending along the extrusion, the cells being bounded by walls dividing adjacent cells from one another. In concert with the extruding, metal is fed through the die with the extruded mix. A length of the extrusion and associated metal is then cut off and fired to form the component.