Appeal 2007-0687
Application 10/797,422
1 Hasz further discloses that it has been discovered that degradation of
2 thermal barrier coatings by environmental contaminants that form molten
3 contaminant compositions can be prevented by depositing impermeable
4 barrier coatings on surfaces of thermal barrier coatings. An impermeable
5 barrier coating inhibits the degradation of the thermal barrier coating when
6 in contact with the molten contaminant composition at operating
7 temperatures of the thermal barrier coating. Hasz, col. 2, ll. 45-53.
8 The impermeable barrier coating prevents infiltration or viscous flow
9 of liquid contaminant compositions into thermal barrier coating cracks,
10 openings, and pores. Hasz, col. 2, ll. 54-56.
11 The impermeable coating is a ceramic or metal outer coating,
12 deposited on the outer surface of the thermal barrier coating. Hasz, col. 3, ll.
13 40-42.
14 Impermeable barrier coatings include aluminum oxide. Hasz, col. 3,
15 ll. 45-52.
16 The impermeable barrier coating may be deposited on the thermal
17 barrier coating by coating methods known in the art, such as sol-gel. Hasz,
18 col. 4, ll. 25-27.
19 Spence discloses a method for reducing coke formation on metallic
20 substrates such as fuel contacting components of gas turbines. Spence, col.
21 3, ll. 9-12.
22 Coke deposition is an undesirable side effect caused by the catalytic-
23 thermal degradation of hydrocarbon fuels during their consumption in gas
24 turbine engines. Spence, col. 1, ll. 14-17.
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