OXIDATION RESISTANT COATING FOR CARBON-CARBON COMPOSITES

THE RESEARCH EFFORT DESCRIBED IN THIS PROPOSAL IS DIRECTED AT DEVELOPING A NOVEL COATING SYSTEM FOR CARBON-CARBON COMPOSITES (CCC) FOR USE AT TEMPERATURES UP TO 2000C. THE OUTER EROSION/CORROSION RESISTANT LAYER IS PLASMA SPRAYED LANTHANUM HAFNATE. THE INNER COATING IS A HIGHLY ADHERENT NOBLE METAL COMPOSITE DIFFUSION BARRIER WITH A VARYING COEFFICIENT OF THERMAL EXPANSION ACROSS ITS THICKNESS. THE SYSTEM IS DESIGNED TO AFFORD MAXIMUM PROTECTION TO CCC BY PROVIDING: 1) A CHEMICALLY INERT DIFFUSION BARRIER FOR CARBON AND OXYGEN. 2) A MEANS OF RELIEVING STRESSES DUE TO THERMAL EXPANSION MISMATCH, AND 3) AN INERT OUTER COATING WHICH IS HIGHLY STABLE IN OXIDIZING ATMOSPHERES AND ALSO MINIMIZES VAPORIZATION LOSS FROM THE NOBLE METAL BARRIER LAYER BELOW.