Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
1998-08-12
2001-10-23
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of metal
C428S472200, C428S937000, C416S24100B
Reexamination Certificate
active
06306515
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally describes multilayer coating systems comprising a composite metal/metal oxide bond coating layer. The coating systems of the present invention may be used in gas turbines.
BACKGROUND OF THE INVENTION
In gas turbine applications, superalloys, MCrAlY bond coatings, and overlay coatings often contain elements such as aluminum or chromium for oxidation and corrosion resistance. One or more of these elements form a thermally grown oxide (TGO) layer on the surface which acts as a barrier to further oxidation and corrosion. Over time, alloying elements like Ti, W, Ta or Hf diffuse up from the substrate and into the thermally grown oxide layer. Such impurities degrade the thermally grown oxide layer and reduce its protective ability. There can also be a significant loss of aluminum via diffusion from the bond coat into the substrate, thereby reducing the aluminum reservoir required to maintain the protective layer.
There is a need in the art for thermal barrier coating systems and overlay coating systems that reduce interdiffusion of elements between the substrate and the bond coat in order to increase the life of the systems. The present invention is directed to these. as well as other, important ends.
SUMMARY OF THE INVENTION
The present invention generally describes multilayer thermal barrier coating systems comprising a thermal barrier coating, layer, a high density metallic bond coating layer, a composite metal/metal oxide bond coating layer and a substrate. The thermal barrier coating systems further comprise a thermally grown oxide layer that forms during manufacture and/or service.
The present invention also generally describes overlay coating systems comprising a high density metallic bond coating layer, a composite metal/metal oxide bond coating layer and a substrate.
The present invention also describes methods of making multilayer thermal barrier coating system comprising depositing a composite metal/metal oxide bond coating layer on a substrate; depositing a high density metallic bond coating layer on the composite metal and oxide bond coating layer; and depositing a thermal barrier coating layer on the high density metallic bond coating layer. The method further comprises heating the multilayer thermal barrier coating system to produce a thermally grown oxide layer between the thermal barrier coating layer and the high density metallic bond coating layer.
The present invention also describes methods of making multilayer overlay coating system comprising depositing a composite metal/metal oxide bond coating layer on a substrate, and depositing a high density metallic bond coating layer on the composite metal/metal oxide bond coating layer.
These and other aspects of the present invention will become clearer from the following detailed description.
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Goedjen John G.
Sabol Stephen M.
Sloan Kelly M.
Vance Steven J.
Eckert Seamans Cherin & Mellott , LLC
Jones Deborah
Siemens Westinghouse Power Corporation
Young Bryant
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