CHEMICAL VAPOR DEPOSITION PROCESSES FOR CERAMIC COATING FOR TITANIUM AND TITANIUM ALLOYS

TITANIUM HAS A UNIQUE COMBINATION OF THERMOPHYSICAL PROPERTIES WHICH RESULT IN OXIDATION SUSCEPTIBILITY. A NUMBER OF COATINGS HAVE BEEN DEVELOPED FOR TITANIUM TO IMPROVE ITS OXIDATION RESISTANCE. COATING PROCESSES FOR TITANIUM PRESENT A VARIETY OF PROBLEMS AND ALL POSSESS LIMITATIONS. CHEMICAL VAPOR DEPOSITION (CVD) PROCESSES HAVE EXCELLENT POTENTIAL TO DEVELOP UNIFORM COATINGS ON COMPLEX GEOMETRIES. CURRENT CVD PROCESSES TO PRODUCE TITANIUM CARBIDE OR TITANIUM DIBORIDE, WHICH ARE COATING CANDIDATES FOR TITANIUM, INVOLVE REACTION TEMPERATURES ABOVE THE PHASE TRANSFORMATION TEMPERATURE OF TITANIUM AND EXPOSE TITANIUM TO ATTACK BY HYDROGEN AND CHLORINE. LOW TEMPERATURE CVD PROCESSES FOR THE FORMATION OF TITANIUM CARBIDE AND TITANIUM DIBORIDE ARE PROPOSED FOR INVESTIGATION. ALL REACTIONS PROPOSED ARE BELOW THE PHASE TRANSFORMATION TEMPERATURE OF TITANIUM. SEVERAL ARE BELOW THE CRITICAL TEMPERATURE FOR THE ONSET OF HYDROGEN REACTIVITY. ALL APPEAR CAPABLE OF DEVELOPING CARBIDE AND DIBORIDE COATINGS WITH EXCELLENT OXIDATION, CHEMICAL AND WEAR RESISTANCE.