Docket # 08-2485-01
Researchers at Princeton have patented a new thermal barrier coating composition to protect aircraft jet engines and turbine engines for electrical power operating at otherwise prohibitively high temperatures. Improvements to the performance of thermal barrier coatings can lead to lower maintenance, lower energy costs, and longer operational lifetimes for coated machine components.
A state-of-the-art thermal barrier coating (TBC) for a nickel-based jet engine consists of a nickel-aluminum alloy bond coat, a thermally protective yttria-stabilized zirconia top coat, and a thin, thermally grown oxide layer of aluminum oxide between the top and bond coats. Growth of the aluminum oxide layer during thermal cycling prevents oxidative corrosion of the engine surface but is a major source of TBC failure. The polycrystalline aluminum oxide layer accumulates stress as it thickens, resulting in grain boundary sliding to relieve stress, subsequent plastic deformation or creep, and eventual peeling away from the engine surface. Early transition metals are commonly added to the bond layer as dopants because they slow both oxide growth and the creep rate to extend the lifespan of the TBC.
Using periodic density functional theory calculations, the Carter Group at Princeton University found that elemental barium raises the activation barrier to grain boundary sliding more than any dopant commonly used in TBCs, including scandium, titanium, yttrium, zirconium, lanthanum, and hafnium. A barium-doped bond coat is thus predicted to reduce grain boundary sliding and prolong the lifetime of the TBC further than currently used dopants. The Carter Group has proposed that adding Ba to the NiAl bond coat alloy as an additional dopant to those already in common use, e.g., Y, Hf, and Pt could extend TBC lifetimes even further.
Princeton is currently seeking an industrial partner to commercialize this technology. For more information, please contact:
John Ritter
Director, Office of Technology Licensing
4 New South
Princeton University, 08544
Phone: 609-258-1570
Email: jritter@princeton.edu
Publications
Milas and E. A. Carter, ¿Effect of Dopants on Alumina Grain Boundary Sliding: Implications for Creep Inhibition, J. Mater. Sci., 44, 1741 (2009).
K. A. Marino, B. Hinnemann, and E. A. Carter, Atomic-scale Understanding Of and Design Principles For Jet Engine Thermal Barrier Coatings From Theory, Proc. Natl. Acad. Sci. U.S.A., 108, 5480 (2011).
Intellectual property
U.S. Patent No. 7,927,714: Barium-doped bond coat for thermal barrier coatings