Appeal No. 2002-0669 2
Application No. 09/527,270
The first layer is a bond coat of MCrAlY allow. The second layer is an inward diffusion
aluminide layer which has a diffusion zone below the surface of the bond coat. The third
layer is a thermal barrier coating. The conditions required by the claimed subject matter
are directed to parameters circumscribed by the term, “about.” The term, “about” is
utilized with respect to the concentration of an activator, the temperature of an aluminiding
reaction and the duration. Additional limitations are present in the following illustrative
claims.
THE CLAIMS
Claims 8 and 15 are illustrative of appellants’ invention and are reproduced below:
8. A process for forming a thermal barrier coating system on a surface of a
superalloy component, the method comprising the steps of:
plasma spraying an MCrAIY bond coat on the surface of the component to
have a surface roughness of at least 300 µinch Ra and a surface area ratio of at least
1.4;
forming an inward diffusion aluminide layer in the surface of the bond coat
using a vapor phase deposition process performed in a coating container and having
process parameters that include a process temperature of about 925oC to about
1040oC and a process duration of four to twelve hours, the vapor phase deposition
process using an aluminum donor containing 50 to 60 weight percent aluminum
and an aluminum halide activator at a concentration of about 1.8 grams of activator
per liter of coating container volume, the inward diffusion aluminide layer causing
the surface of the bond coat to have an aluminum concentration of at least 30
weight percent while maintaining a surface roughness of at least 300 µinch Ra and
a surface area ratio of at least 1.4; and
depositing a ceramic layer on the bond coat.
15. A process for forming a thermal barrier coating system on a surface of a
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