TECHNICAL: This grant supports fundamental research that explores the influence of coating chemistry and microstructure on the mechanical properties and oxidation resistance of novel NiAl-Hf overlay bond coatings. The coatings are designed for use in high-temperature structural applications. The research relies on the application of novel micromechanical and analytical techniques to characterize the microstructures and properties of multiphase, sputter-deposited overlay coatings. The technological motivation is development of novel coatings that will increase the capability and durability of emerging engineering structures targeted for high-temperature structural applications. While this program is primarily directed towards the development of bond coatings for thermal barrier coating systems, related applications include environmental barrier coatings for silicon-based ceramics and overlay coatings for high speed cutting tools. A basic understanding of the changes in coating properties produced by microstructural modification (i.e., grain morphology and precipitate distribution) will open new horizons for the development and application of thinner, more durable coatings. NONTECHNICAL: This project has a positive impact on science and engineering infrastructure through the training of graduate students. The two graduate students in the project employ aspects of surface science, physical chemistry, metallurgical and ceramic engineering, thin film science, materials processing, microstructural characterization, and materials selection. The students benefit by being involved in advanced research in the micromechanical, chemical, and microstructural characterization of multilayered materials. They utilize state-of-the-art analytical tools. The integration of undergraduate students from the freshman and sophomore classes at the University of Alabama and from neighboring HBCU's provides those students with practical laboratory experiences above and beyond that normally associated with their academic coursework. In addition, the relevance of the project to advanced coating technologies provides a strong practical motivation for the work in addition to ensuring good career options for the students involved.
