The proposed metal chromium-aluminum-yttrium (MCrAlY; where M = nickel [Ni], cobalt [Co] or a mixture of Ni and Co) bond coats will be synthesized via an electrolytic codeposition process, followed by a post-plating heat treatment. In contrast to traditional electro-codeposition processes where sulfate or sulfamate bath is used for Ni/Co deposition, a sulfur-free electrolyte will be employed to control the impurity levels in the MCrAlY coatings. The reduced sulfur (S) levels will be expected to improve oxide scale adhesion. The amounts of Cr, Al, and particularly the Y reservoir, in the MCrAlY bond coat will be optimized to extend the lifetime of the thermal barrier coating (TBC) system. Reactive elements such as Y + hafnium (Hf) or Y + zirconium (Zr) will be co-doped into the MCrAlY coatings by modifying the composition of the CrAlY alloy powder. The composition of the CrAlY+ alloy (where "+" equals Hf or Zr, etc.) will be carefully designed, based on the literature data for model MCrAlY alloys and other types of MCrAlY coatings. Other parameters of the electrolytic codeposition process will be systematically studied using a design-of-experiment approach to provide a fundamental understanding of their synergistic effects and to optimize the coating composition and microstructure.
This project will utilize a novel coating process to synthesize a nickel/cobalt- chromium-aluminum-yttrium (MCrAlY) bond coat. Turbine materials research seeks to improve coating materials that will allow for higher temperature operation and increased durability leading to increased turbine efficiency and reduced maintenance. Specifically, this project will use electro-codeposition to deposit optimally designed MCrAlY bond coats using a sulfur free electrolyte and analyze the process and resulting bond coats for effects on composition and microstructure.
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