Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1998-12-14
2003-03-04
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S469000, C428S627000, C428S632000, C428S650000, C428S655000, C428S668000, C428S680000, C416S24100B
Reexamination Certificate
active
06528189
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an article of manufacture, including a substrate formed of a nickel or cobalt-based superalloy, an anchoring layer placed on the substrate and a ceramic coating placed on the anchoring layer. The invention also relates to a method of placing a ceramic coating on an article of manufacture including a substrate formed of a nickel or cobalt-based superalloy, the method which includes placing an anchoring layer on the substrate and placing the ceramic coating on the anchoring layer.
The invention in particular relates to an article of manufacture to be used as a gas turbine component which is subjected to a hot and oxidizing gas stream streaming along it in operation. Such gas turbine components include gas turbine airfoil components like blades and vanes as well as gas turbine heat shield components.
U.S. Pat. No. 4,055,705 to Stecura et al.; U.S. Pat. No. 4,321,310 to Ulion et al., and U.S. Pat. No. 4,321,311 to Strangman disclose coating systems for gas turbine components made from nickel or cobalt-based superalloys. A coating system described includes a thermal barrier layer made from ceramic, which in particular has a columnar grained structure, placed on a bonding layer or bond coating which in its turn is placed on the substrate and bonds the thermal barrier layer to the substrate. The bonding layer is made from an alloy of the MCrAlY type, namely an alloy containing chromium, aluminum and a rare earth metal such as yttrium in a base including at least one of iron, cobalt and nickel. Further elements can also be present in an MCrAlY alloy; examples are given below. An important feature of the bonding layer is a thin layer developed on the MCrAlY alloy and used for anchoring the thermal barrier layer. This layer may be alumina, alumina mixed with chromium oxide or a double layer of alumina facing the thermal barrier layer and chromium oxide facing the bonding layer, depending on the composition of the MCrAlY alloy and the temperature of the oxidizing environment where the layer is developed. Eventually, an alumina layer may be placed purposefully by a separate coating process like physical vapor deposition (PVD).
U.S. Pat. No. 5,238,752 to Duderstadt et al. discloses a coating system for a gas turbine component which also incorporates a ceramic thermal barrier layer and a bonding layer or bond coating bonding the thermal barrier layer to the substrate. The bonding layer is made from an intermetallic aluminide compound, in particular a nickel aluminide or a platinum aluminide. The bonding layer also has a thin alumina layer which serves to anchor the thermal barrier layer.
U.S. Pat. No. 5,262,245 to Ulion et al. describes a result of an effort to simplify coating systems incorporating thermal barrier layers for gas turbine components by avoiding a bonding layer to be placed below the thermal barrier layer. To this end, a composition for a superalloy is disclosed which may be used to form a substrate of a gas turbine component and which develops an alumina layer on its outer surfaces under a suitable treatment. That alumina layer is used to anchor a ceramic thermal barrier layer directly on the substrate, eliminating the need for a special bonding layer to be interposed between the substrate and the thermal barrier layer. In its broadest scope, the superalloy is formed essentially of, as specified in weight percent: 3 to 12 Cr, 3 to 10 W, 6 to 12 Ta, 4 to 7 Al, 0 to 15 Co, 0 to 3 Mo, 0 to 15 Re, 0 to 0.0020 B, 0 to 0.045 C, 0 to 0.8 Hf, 0 to 2 Nb, 0 to 1 V, 0 to 0.01 Zr, 0 to 0.07 Ti, 0 to 10 of the noble metals, 0 to 0.1 of the rare earth metals including Sc and Y, balance Ni.
U.S. Pat. No. 5,087,477 to Giggins, Jr., et al. shows a method for placing a ceramic thermal barrier layer on a gas turbine component by a physical vapor deposition process including evaporating compounds forming the thermal barrier layer with an electron beam and establishing an atmosphere having a controlled content of oxygen at the component to receive the thermal barrier layer.
U.S. Pat. No. 5,484,263 to B. A. Nagaraj et al. shows a metal article having a heat shield including: a barrier layer on a surface of the article and a reflective layer on the barrier layer. The reflective layer being formed from a material which is selected from the group formed of the noble metals, noble metal alloys and aluminum. The barrier layer may be an oxide or a nitride.
European Patent Application 0 446 988 A1 to V. Andoncecchi et al. shows a process for forming a silicon carbide coating on a nickel-based superalloy, including nitriding pretreatment of the superalloy or deposition of a film of titanium nitride on the superalloy by reactive sputtering. Thereafter a thin film of titanium nitride is being deposed using vapor-phase chemical deposition. After this the nickel-based superalloys annealed in a nitrogen and hydrogen atmosphere and a silicon carbide layer is placed using vapor-phase chemical deposition. With this process a coating is obtained wherein between a ceramic layer containing silicion carbide or silicion nitride and a superalloy an intermediate layer containing titanium nitride is being interposed.
European Patent Application 0 688 889 A1 to P. Broutin et al. shows a process for passivating the surface of a metallic article formed of a nickel-based superalloy. This metallic article is a stove-pipe or the like. On the substrate formed of the nickel-based superalloy a protective layer is applied containing silicion carbide or silicion nitride. Between the ceramic protective layer and the substrate an intermediate layer formed of aluminum nitride or titan aluminum nitride is interposed. The intermediate layer has a thickness of 0.15 to 5 &mgr;m which is less than a thickness of the protective layer.
U.S. Pat. Nos. 5,154,885; 5,268,238; 5,273,712; and 5,401,307, all to Czech et al. disclose advanced coating systems for gas turbine components including protective coatings of MCrAlY alloys. The MCrAlY alloys disclosed have carefully balanced compositions to give exceptionally good resistance to corrosion and oxidation as well as an exceptionally good compatibility to the superalloys used for the substrates. The basis of the MCrAlY alloys is formed by nickel and/or cobalt. Additions of further elements, in particular silicon and rhenium, are also discussed. Rhenium in particular is shown to be a very advantageous additive. All MCrAlY alloys shown are also very suitable as bonding layers for anchoring thermal barrier layers, particularly in the context of the invention disclosed hereinbelow.
The aforementioned U.S. Pat. No. 5,401,307 also contains a survey over superalloys which are considered useful for forming gas turbine components that are subject to high mechanical and thermal loads during operation. Particularly, four classes of superalloys are given. The respective superalloys are formed essentially of, as specified in percent by weight:
1. 0.03 to 0.05 C, 18 to 19 Cr, 12 to 15 Co, 3 to 6 Mo, 1 to 1.5 W, 2 to 2.5 Al, 3 to 5 Ti, optional minor additions of Ta, Nb, B and/or Zr, balance Ni. These alloys are brought into shape by forging; examples are specified as Udimet 520 or Udimet 720 by usual standard.
2. 0.1 to 0.15 C, 18 to 22 Cr, 18 to 19 Co, 0 to 2 W, 0 to 4 Mo, 0 to 1.5 Ta, 0 to 1 Nb, 1 to 3 Al, 2 to 4 Ti, 0 to 0.75 Hf, optional minor additions of B and/or Zr, balance Ni. These alloys are cast into shape; examples are GTD 222, IN 939, IN 6203 DS and Udimet 500.
3. 0.07 to 0.1 C, 12 to 16 Cr, 8 to 10 Co, 1.5 to 2 Mo, 2.5 to 4 W, 1.5 to 5 Ta, 0 to 1 Nb, 3 to 4 Al, 3.5 to 5 Ti, 0 to 0.1 Zr, 0 to 1 Hf, an optional minor addition of B, balance Ni. These alloys are cast into shape; examples are IN 738 LC, GTD 111, IN 792 and PWA 1483 SX.
4. 0.2 to 0.7 C, 24 to 30 Cr, 10 to 11 Ni, 7 to 8 W, 0 to 4Ta, 0 to 0.3 Al, 0 to 0.3 Ti, 0 to 0.6 Zr, an optional minor addition of B, balance cobalt. These alloys are cast into shape; examples are FSX 414, X 45, ECY 768 and MAR-M-509.
A standard practice in placing a thermal barrier coating o
Greenberg Laurence A.
Jones Deborah
Locher Ralph E.
McNeil Jennifer
Siemens Aktiengesellschaft
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