Recovery Act - Microcomposite Coatings for Advanced Heat Exchangers
Next generation heat exchangers will operate at higher pressures and temperatures than current models in order to increase cycle efficiency, reduce fuel consumption and emissions. Ultra-supercritical coal-fired boilers can generate electric power with low emissions while burning high-sulfur coal and can increase efficiency from ~28% to >46%. The problem lies in the materials that are currently used. Current materials solutions include nickel-based superalloys, but these are prohibitively expensive. This project has sought to bypass this issue through the development of microcomposite coatings that are resistant to erosive wear, creep and gas corrosion at elevated temperatures. During the Phase I project, several aluminide coating formulations were evaluated for durability in simulated operational environments. One of the major obstacles that had to be overcome was the mismatch of the coefficient of thermal expansion between the coating and the substrate. This hurdle was overcome through the use of ceramic additions to the coating that enabled the CTE of the coating to match the substrate. These ceramic additions were both manufactured into the coating material and developed in-situ during the coating process through controlled thermite reactions to form a fine dispersion of alumina in an aluminide matrix. Commercial Applications and Other Benefits: The Phase II will continue to study the use of exothermic reactions to improve coating properties and to generate durable coating materials. Additional work in the Phase II project will explore the development of additional coating compositions to further improve erosion resistance and to meet the environmental conditions in other applications. The work will culminate in the cladding of a boiler tube section for evaluation in a sub-scale supercritical boiler testing facility.
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24112 Rockwell Dr. Euclid, OH 44117
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