Available Technology

Method of Applying a Cerium Diffusion Coating to a Metallic Alloy

The Department of Energy’s National Energy Technology Laboratory (NETL) is seeking licensing partners interested in implementing United States Patent Number 7,553,517 titled "Method of Applying a Cerium Diffusion Coating to a Metallic Alloy." This invention is applicable to advanced, next-generation power plant components; solid oxide fuels cells; heaters and heat exchangers; or any other application where oxidation-resistant metals are needed.
In order to produce power more efficiently and cleanly, the next generation of power plant boilers, turbines, solid oxide fuel cells (SOFCs) and other essential equipment will have to be operated at extreme pressures and temperatures, in what is known as the "ultrasupercritical" range. This range involves pressures up to 5,400 psi and temperatures up to 1,400°F. Even nickel-based superalloys and stainless steels suffer from excessive oxidation at these conditions, leading to the premature failure of components. A possible solution is to coat the metallic components with a protective layer of a ceramic oxide such as cerium oxide, then thermally treat the alloy so that Ce diffuses into the surface of the bulk metal alloy. Researchers at NETL have developed a simple and robust method of applying a CeO2 slurry with an activator compound to the surface of a metal component by brushing, spraying, or dipping. This low-cost process ensures a uniform coating on parts of complex shapes that are difficult to coat using sputtering, vapor deposition, or traditional pack cementation. Analysis of the coatings after thermal treatment showed that the CeO2 reacts with the metal surface to form a Ce-rich layer, with a Cr-Mn sublayer, resulting in a protective surface layer with a microstructure that greatly slows the oxidation rate. In most cases, the cerium surface treatment improved oxidation resistance by a factor of 2 to 3, and in a few alloys it resulted in to an order of magnitude improvement in performance.
A method of modifying the surface of nickel superalloys or stainless steels to impart oxidation resistant properties through Ce diffusion -A means of increasing the oxidation resistance properties of metal alloys by a factor of 2 to 3 in most cases -A way to reduce the migration of Cr from the interconnect plates of solid oxide fuel cells
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