Process of making an article having a hard carbide, boride or silicide outer region

Claim 1

IN THE PROCESS FOR MAKING AN ARTICLE HAVING AT LEAST AN OUTER LAYER OF SUBSTANTIAL THICKNESS CONTAINING AT LEAST ONE HARD, HIGH MELTING POINT CARBIDE, COMPRISING THE STEPS OF: (A) INFILTERING A PERMEABLE FRAMEWORK WHICH IS EESSENTAILLY ELEMENTAL CARBON WITH A LIQUID METALLIC MATERIAL COMPRISING AT LEAST ONE METALLIC ELEMENT CAPABLE OF CHEMICALLY COMBINING WITH THE FRAMEWORK MATERIAL TO FORM AT LEAST ONE HARD, HIGH MELTING POINT CARBIDE, SAID INFILTRATION BEING CARRIED OUT AT A TEMPERATURE SUFFICIENTLY LOW THAT SAID METALLIC MATERIAL REMAINS IN THE LIQUID PHASE THROUGHOUT THE INFILTRATION OF SAID FRAMEWORK, SAID INFILTRATION BEING CONTINUED UNTIL SUBSTANTIALY ALL OF THE VOIDS IN SAID FRAMEWORK ARE SUBSTANTIALLY COMPLETELY FILLED TO AT LEAST A DEPTH SUFFICIENT TO PERMIT REMOVAL OF AN OUTER PORTION OF SAID ARTICLE OF SUBSTANTIAL THICKNESS WITHOUT DESTROYING MORE THAN A MINOR OUTER PORTION OF THE INFILTERED REGION; AND (B) SUBJECTING THE INFILTERED FRAMEWORK TO CARBIDE FORMING PRESSURE AND TEMPERATURE CONDITIONS FOR A SUFFICIENTLY LONG TIME TO CHEMICALLY COMBINE AT LEAST A PORTION OF SAID FRAMEWORK WITH AT LEAST ONE ELEMENT IN SAID METALLIC MATERIAL TO FORM AT LEAST ONE HARD, HIGH MELTING POINT CARBIDE; THE IMPROVEMENT OF ADDING TO SAID METALLIC MATERIAL BEFORE THE INFILTRATION OF SAID FRAMEWORK CERIUM IN AN AMOUNT SUFFICIENT TO REDUCE THE SIZE OF THE PARTICLES PRODUCED IN THE REACTION OF THE METALLIC MATERIAL WITH THE FRAMEWORK AND IN THE RANGE OF FROM ABOUT 0.1 TO ABOUT 10 PERCENT OF THE METALLIC MATERIAL.