Kinetic Metallization of Oxidation Resistant Coatings for Ultrasupercritical Coal-Fired Boilers

New ferritic, austenitic, and nickel-base alloys have been designed to meet the creep resistance properties for ultrasupercritical coal-fired boilers, an emerging technology that offers increased power-generating efficiency. However, the high operating temperatures and harsh chemically-reactive environments subject these materials to oxidation and corrosion degradation. Thus, oxidation- and corrosion-resistant coatings are required to protect these structures and to extend operating life. Aluminide materials, deposited using chemical vapor desposition (CVD) and pack-cementation processes, can provide superior oxidation and corrosion coatings for these boiler materials, because they form a protective alumina layer at the surface. Unfortunately, these processes are not suitable for production-scale coating of large surfaces. This project will investigate the suitability of an FeCrAlY alloy, which will be spray-deposited onto ferritic, austenitic, and nickel-base alloys using the emerging Kinetic Metallization process. Phase I will determine the feasibility of depositing these ferritic FeCrAlYcoatings on the above alloys. The coatings will be tested in a humid environment at 700oC. The ability of the coatings to maintain a sufficient aluminum reserve, in order to extend the lifetime of the coating from losses due to alumina surface scaling and substrate diffusion in the operating environment, will be determined. Commercial Applications and Other Benefits as described by the awardee: The Kinetic Metallization process should provide a low cost method of spraying boiler tubes and structures with oxidation and corrosion resistant coatings at high density. Because the Kinetic Metallization process is performed at low temperatures, the coating can be applied without compromising the mechanical strength and properties of ferritic, austenitic, and nickel-based alloy structures. The technology would extend the life of ultrasupercritical coal-fired boilers, which would be used by the coal-fired power generation industry. Secondary commerical applications would be likely in the aerospace industries, where gas turbine engines require more stable coatings at high operating temperatures.