CAREER: Coatings for High Temperature Alloys

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9624927 Hampikian Combustion chemical vapor deposition (CVD) is a novel approach to chemical vapor deposition. Because CVD is carried out in an open atmosphere, it has the potential to be a new cost-effective coating process. In this CAREER program coatings of alumina are applied to prototype nickel- base alloys to assess improvements in oxidation imparted to the alloys by the CVD coatings. Several key issues related to reactive element effects are examined through use of CVD applied coatings containing various concentrations of reactive element dopants. The effectiveness of reactive element additions in suppressing cationic diffusion in alumina scales is addressed through study of doped and undoped alumina scales and subsequent characterization. The mechanism of such suppression is explored for a critical concentration effect to ascertain the validity of the segregant/defect pair postulate. The mechanism of degradation of the uncoated and coated alloys to high temperature corrosion is explored with the goal of adding significantly to the current knowledge base in this area. %%% Work of this type is vital for optimum design of coating systems for parts experiencing aggressive environments. For example thin ceramic coatings can be used to improve the corrosion resistance of bulk materials. The coatings act as barriers between the environment and the substrate to protect the substrate from erosion and gaseous and liquid corrodants. ***