GOALI: Comibinatorial Methods and Micro-Scale Characterization Techniques for TBC Optimization

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This GOALI grant from the Division of Materials Research to Johns Hopkins University is to employ combinatorial methods and micro-scale testing to elucidate the role of alloy chemistry on the martensite transformation in bond coats for thermal barrier coatings (TBCs) applied to superalloys. With this award, Professors Hemker and Zhao will be opening a new paradigm for bond coat design, and the research will promote the development of experimental tools needed to advance new materials into a variety of structural applications. This grant is motivated by the recent discovery of martensite transformation occurring in thermally cycled, platinum modified, nickel aluminide bond coats. This transformation has been shown to dramatically influence the performance of the TBC and is known to be highly dependent on alloy chemistry, which can vary as a result of element interdiffusion. The use of diffusion multiples provides a highly efficient means for clarifying the role that stoichiometry and ternary elements (e.g. Platinum, Chromium, Rhenium, Tungsten, Molybdenium, Tantalum, Cobalt and Hafnium) will have in governing martensite formation. Targeted thin film combinatorial samples of specific compositions, determined using diffusion multiples, are fabricated with inert plasma deposition and characterized with a suite of novel micro-scale characterization techniques (micro-tensile testing, nanoindentation, micro-probe spectroscopy, differential thermal analysis, X-ray diffraction and transmission electron microscopy). The results should provide a fundamental understanding of the martensite transformation that occurs in TBC bond coats and thereby provide a science-based protocol for the development of long lasting, high performance TBC coatings. The technological motivation for this research is rooted in the fact that thermal barrier coatings offer tremendous opportunities for increasing the temperature capabilities and durability of components in aircraft engines and power turbines. In addition, the scientific challenges to be addressed, namely the development of combinatorial methods and novel micro-scale characterization techniques for assessing the stability, strength and performance of multilayered coatings, have a much broader application for the development of multicomponent structural materials. This Grant Opportunities for Academic Liaison with Industry (GOALI) collaboration includes closely meshed research activities and yearly personnel exchanges, and places Johns Hopkins students and faculty in direct contact with engineers and scientists at the GE Global Research Center. This broadens the education of the JHU students by providing invaluable technological and industrial experience. The benefits to GE include the availability of unique JHU experimental expertise and the ability to focus on fundamental research in an area that is of high technological interest.