Nanostructured Coatings by Pulsed Plasma Processing for Alloys used in Coal-Fired Environments

The efficient and profitable operation of coal-fired power plants requires higher steam temperatures and pressures, necessitating the use of advanced alloys. A major concern in using these advanced materials is their poor corrosion and oxidation resistance in fossil energy environments. Therefore, protective coatings on the ferritic and austenitic steels used in these coal-fired environments are needed to assure the economic and safe operation of the power plants. This project will develop an innovative plasma coating technology to apply durable nanostructured coatings of iron and nickel aluminide on Fe- and Ni-based alloys. Phase I demonstrated the feasibility of depositing nanostructured coatings of Ni3Al and Fe3Al on substrates of 304L and P91 steels. Coated samples were characterized by chemical, physical, structural, and microscopical techniques. The performance of plasma-coated samples was compared with uncoated samples in a simulated furnace environment. Phase II will optimize the coating chemistry and demonstrate the scalability of the process to coat tubes upto 24¿ in length. The performance of coatings will be evaluated in simulated and real coal gasification environments.Commercial Applications and other Benefits as described by the awardee: The coating technology should have a significant impact on the electrical utility industry by saving the materials costs involved in replacing corroded tubes, reducing downtime, increasing efficiency in power generation, and reducing the probability of a catastrophic failure. The technology is versatile and could be extended to materials or components used in other industrial applications. Because the technology is not a line-of sight process, it could be used to coat complex shaped components. Lastly, the process is highly energy efficient and could be automated.