Process for producing oxidation resistant refractory coating on dense graphite

Claim 1

IN A PROCESS FOR PRODUCING A HIGH TEMPERATURE OXIDATION RESISTANT REFRACTORY COATING ON DENSE NUCLEAR GRADE GRAPHITE HAVING AN ISOTROPIC COEFFICIENT OF THERMAL EXPANSION IN THE RANGE OF 3 TO 8X10**-6 IN./IN./*C., THE STEPS COMPRISING APPLYING SUBSTANTIALLY OXIDE-FREE SILICON METAL TO SAID POROUS SURFACE IN LIMITED QUANTITIES WHILE MAINTAINED AT AN ELEVATED TEMPERATURE ABOVE THE MELTING POINT OF SILICON TO REACT THEREWITH AND PRODUCE THEREON A COMPOSITE LAYER OF SILICON CARBIDE INTERPENETRATED BY LOCALIZED RESIDUAL GRAPHITE REGIONS OF SAID SURFACE, REMOVING EXPOSED PORTIONS OF SAID RESIDUAL GRAPHITE REGIONS FROM SAID CARBIDE LAYER BY CONTACT WITH AN OXIDIZING ATMOSPHERE AT ELEVATED TEMPERATURES TO PRODUCE A POROUS EXTERIOR SURFACE THEREON, WHEREBY SAID LAYER MAY SERVE AS AN INTERMEDIATE BONDING LAYER, AND APPLYING MOLTEN SILICON METAL TO SAID POROUS EXTERIOR SURFACE OF SAID CARBIDE LAYER TO PROVIDE AN ADHERENT CONTINUOUS LAYER OF SILICON METAL COATING BONDED TO THE GRAPHITE BY SAID INTERMEDIATE CARBIDE LAYER.