Low-Cost Alloy Coatings by Pulsed Electrodeposition for Combustors

A need has been identified for new fabrication methods to enable production of low-cost combustors for biomass with enhanced durability against high temperatures and corrosive environments. Biomass represents an abundant, renewable fuel source with significant unrealized potential to supplant nonrenewable fossil fuels in providing for the Nations energy needs. Cost concerns typically require that combustor hardware be composed of mild or low-alloy steels, which do not possess the required material properties to achieve acceptable lifetimes in biomass combustion applications. Accordingly, interest has been expressed in development of novel, low-cost approaches for fireside surface modifications of the base steel that will provide the desired thermal and chemical resistances. Identify and develop corrosion-resistant cobalt-chromium-molybdenum coatings for the inner surfaces of low-alloy steel biomass combustors to provide the necessary resistance to high temperatures 600-900 C) and corrosion from attack by alkali halides and water. Demonstrate the capability of pulsed electrodeposition to fabricate suitable coatings on the coupon scale, with scale-up in Phase II to coating electrodeposition and testing of combustor bodies on a demonstration scale. Various experimental electrodeposition conditions will be explored to determine those that afford cobalt-chromium-molybdenum coatings of varying composition on test substrates. These coatings will be evaluated for properties such as uniformity, adhesion, and thermal expansion coefficient match, after which the coating compositions will be down-selected to the most promising candidates, and applied to low-alloy steel coupons for corrosion testing in a simulated biomass combustion environment at 600-900 C. Results will inform the design of coating deposition and performance testing and apparatus for Phase II demonstration-scale combustors. Economic and market evaluation of the proposed coating technology will also be performed. Economical application of corrosion-resistant cobalt- chromium-molybdenum coatings to steel biomass combustors has the potential to facilitate enhanced economics and utilization of biomass as an energy source. Improved combustor technology will decrease the cost-of-ownership; integration with other technological advances catalytic converters) would presumably increase the extractible energy per mass of fuel, further enhancing cost-effectiveness. The technology has the potential to facilitate a transition of large-scale electrical generation from non- renewable fossil fuels to renewable biomass. The potential global market for generation steadily increasing from 14.6 petawatt-hours of fossil-fired generation in 2011) is substantial. The public benefit from reduced electricity prices and decreased net greenhouse gas emissions is anticipated to be significant.