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.
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.
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.
currently seeking an industrial partner to commercialize this technology. For
more information, please contact:
Director, Office of
4 New South
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).
U.S. Patent No. 7,927,714:
Barium-doped bond coat for thermal barrier coatings