Process for making silicon carbide reinforced silicon carbide composite

A process comprising the steps of:

• a) providing a fiber preform comprising:
• i) between 20 vol % and 80 vol % coated fiber, the fiber comprising silicon carbide, and
• ii) between 20 vol % and 80 vol % porosity,
• b) impregnating a slurry comprising ceramic particles into the porosity of the fiber preform to form a green body having a porosity which is lower than the porosity of the fiber preform and an exterior surface, and
• c) depositing ceramic particles on the exterior surface of the green body to form a monolithic layer of ceramic particles on the exterior surface of the green body, and
• d) green machining the monolithic layer to a surface roughness Ra of no more than 200 .mu.inches.

A process comprising the steps of:

• a) providing a green body comprising:
• i) between 20 vol % and 80 vol % coated fiber, the fiber comprising silicon carbide, and
• ii) between 20 vol % and 80 vol % porosity,
• b) soaking the preform in a solution consisting essentially of water and a surfactant,
• c) providing a porous mold,
• d) placing the soaked fiber preform in the mold,
• e) contacting the fiber preform with a slurry comprising water and ceramic particles to infiltrate the porosity of the fiber preform with the ceramic particles of the slurry, and
• f) pressure casting the slurry to form a green body having a porosity which is lower than that of the fiber preform.

A pressure casting process for producing an impregnated fiber preform, comprising the steps of:

• a) providing a fiber preform comprising:
• i) between 20 vol % and 80 vol % coated fiber, the fiber comprising silicon carbide,
• ii) between 20 vol % and 80 vol % porosity,
• b) providing a porous mold,
• c) placing the fiber preform in the mold,
• d) contacting the fiber preform with a slurry comprising water and ceramic particles to infiltrate the porosity of the fiber preform with the ceramic particles of the slurry, and
• e) pressure casting the slurry to form a green body having a porosity which is lower than that of the fiber preform.

A process comprising the steps of:

• a) providing a fiber preform comprising a non-oxide ceramic fiber having at least one coating, the coating comprising silicon carbide, the fiber having a degradation temperature of between 1410.degree. C. and 1450.degree. C.
• b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon to produce an impregnated green body,
• c) providing a cover mix comprising:
• i) an alloy comprising silicon and between 0.003 wt % and 10 wt % carbon dissolved therein, and
• ii) a resin,
• d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body,
• e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and
• f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite having less than 3 vol % in-situ formed silicon carbide and less than 1% porosity.