Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2002-05-29
2004-01-13
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S469000, C428S472000, C428S701000, C428S697000, C428S699000, C428S937000, C416S24100B
Reexamination Certificate
active
06677064
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to the field of thermal barrier coatings and, in particular, to multiphase ceramic thermal barrier coatings used in high temperature applications for coating superalloy components of a combustion turbine engine.
BACKGROUND OF THE INVENTION
Many power generation plants produce electricity by converting potential energy (e.g. fossil fuel) into mechanical energy (e.g. rotation of a turbine shaft), and then converting the mechanical energy into electrical energy (e.g. by the principles of electromagnetic induction). These power generation plants typically use a turbine to convert the potential energy into mechanical energy and a generator to convert the mechanical energy into electricity.
One aspect of the above-described power generation scheme involves the use of increasingly higher combustion temperatures within the combustion portion of the turbine to improve the turbine efficiency of combustion turbine. Turbine components must therefore be capable of withstanding the increasingly higher temperatures from the combustion gas flow path for prolonged sustained periods of time, which can exceed 1200° C. and even 1400° C.
The turbine components are typically made of temperature resistant nickel or cobalt based “superalloy” materials. These superalloy components are typically further protected by an alumina or MCrAlY basecoat. The basecoat is then typically covered by a ceramic thermal barrier coating (“TBC”), such as stabilized zirconia, for example, 8 wt. % yttria stabilized zirconia (“8YSZ”). The TBC provides low thermal conductivity with low coefficient of thermal expansion mismatch with the basecoat and/or superalloy substrate.
TBCs are typically deposited as a generally columnar grain structure with discrete intercolumnar gaps or cracks that extend generally perpendicular to the top surface of the substrate, as taught for example, in U.S. Pat. No. 4,321,311. This columnar structure is typically formed by plasma assisted physical vapor deposition, electron beam physical vapor deposition, ion beam irradiation, and the like. Alternatively, TBCs are also typically deposited as a generally flat grain structure with discrete cracks or pores that extend generally parallel to the top surface of the substrate, as taught for example, in U.S. Pat. No. 6,294,260. This flat type of coating structure tends to have a poorer erosion resistance but a lower thermal conductivity than columnar structures, and is typically formed by air plasma spraying techniques and the like.
However, currently used air plasma sprayed (“APS”) and/or physical vapor deposited (“PVD”) YSZ TBCs tend to destabilize after prolonged sustained exposure to temperatures above approximately 1200° C. Such prolonged sustained high temperature exposure can also lead to potential sintering and loss of strain compliance, as well as possible premature TBC failure. YSZ and similar TBCs are also susceptible to corrosion upon exposure to contaminants in the fuel and erosion due to foreign object damage.
U.S. Pat. Nos. 6,294,260 and 6,296,945 to Subramanian disclose certain multiphase TBCs adapted for prolonged exposure to temperatures above approximately 1200° C. and even above approximately 1400° C. These multiphase TBCs comprise the reaction product of a ceramic oxide base layer material having the composition (A,B)xOy and a ceramic oxide overlay precursor material having the composition CzOw. Multiphase TBCs possess a unique set of properties, which the individual constituents may not provide.
However, multiphase TBCs can tend to be relatively difficult to chemically form, manufacture, or arrange onto a basecoat or superalloy substrate, as well as relatively expensive. There is thus a need to continue and improve upon the existing multiphase TBCs adapted for prolonged exposure to temperatures above approximately 1200° C. and even above approximately 1400° C. There is also a need for new and additional multiphase TBCs that tend to be relatively easier to chemically form, manufacture, or arrange onto a basecoat or superalloy substrate, as well as relatively less expensive than that of the prior art.
SUMMARY OF THE INVENTION
The present invention provides new and additional multiphase TBCs that tend to be relatively easier to chemically form, manufacture, or arrange onto a basecoat or superalloy substrate, as well as relatively less expensive than that of the prior art. The present invention also continues and improves upon existing multiphase TBCs adapted for prolonged exposure to temperatures above approximately 1200° C. and even above approximately 1400° C.
One aspect of the present invention thus involves a multiphase ceramic thermal barrier coating adapted for use in high temperature applications for coating superalloy components of a combustion turbine engine. The coating comprises a ceramic single or two oxide base layer disposed on the substrate surface; and a ceramic oxide reaction product material disposed on the base layer, the reaction product comprising the reaction product of the base layer with a ceramic single or two oxide overlay layer.
Another aspect of the invention involves a device adapted for use in a high temperature environment in excess of about 1200° C., comprising a substrate having a surface; a ceramic single oxide base layer disposed on the substrate surface; and a ceramic oxide reaction product material disposed on the base layer, the reaction product comprising the reaction product of the base layer with a ceramic single oxide overlay layer, wherein the single oxide base layer comprises a composition having the formula CzOw and the single oxide overlay layer comprises a composition having the formula AxOy, wherein C and A are selected from the group consisting of: Al, Ca, Mg, Zr, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Ta, Nb, z and x are selected from the group of integers consisting of: 1, 2, 3, and 4, and w and y are selected from the group of integers consisting of: 1, 2, 3, 4 and 5.
Another aspect of the invention involves a device adapted for use in a high temperature environment in excess of about 1200° C., comprising a substrate having a surface; a ceramic two-oxide base layer disposed on the substrate surface; and a ceramic oxide reaction product material disposed on the base layer, the reaction product comprising the reaction product of the base layer with a ceramic two-oxide overlay layer, wherein the two-oxide base layer comprises a composition having the formula (C,D)
w
,O
z
and the two-oxide overlay layer comprises a composition having the formula (A,B)xOy, wherein C, D, A and B are selected from the group consisting of: Al, Ca, Mg, Zr, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Ta, Nb, w and x are decimals ranging from about 0.5 to about 1.5, and z and y are decimals ranging from about 0.5 to about 2.0.
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Jones Deborah
McNeil Jennifer
Siemens Westinghouse Power Corporation
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