Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1999-01-29
2001-02-20
Jenkins, Daniel J. (Department: 1742)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C075S255000, C075S338000, C075S351000, C427S456000, C427S123000, C427S208200, C427S229000, C427S328000, C427S376800
Reexamination Certificate
active
06190785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a spray coating powder material having excellent high-temperature corrosion resistance and hence suitable for use with moving and stationary blades of gas turbines, as well as high-temperature components coated therewith. Moreover, it also relates to a spray coating powder material having excellent high-temperature corrosion resistance and hence suitable for use with burner diffusers and other components for boilers, as well as high-temperature components coated therewith.
2. Description of the Related Art
Recently, the development of gas turbines using a low-quality fuel oil as fuel is being carried on from the viewpoint of resources saving, fuel cost reduction and the like. However, such low-quality fuel oils contain large amounts of constituents accelerating the corrosion of metals, such as sulfur, vanadium and sodium, so that moving and stationary blades which are high-temperature components of gas turbines are exposed to a very severe corrosive environment. In such an environment, base metals comprising conventional heat-resisting alloys and heat-resisting steel fail to show sufficient corrosion resistance and hence undergo accelerated deterioration with time. In the existing state of the art, therefore, the corrosion resistance of base metals comprising heat-resisting alloys and heat-resisting steel is secured by coating them with a powder material to a thickness of about 100-400 &mgr;m according to a plasma spraying technique. The power materials conventionally used for this purpose include, for example, Ni-50% Cr and MCrAlY materials (in which M represents Co, Ni, Fe or the like). that have been evaluated to have excellent corrosion resistance.
More recently, cruder low-quality fuel oils [for example, fuel oil C containing 10 to 30 mg/kg of sodium (Na), potassium (K) and vanadium (V)] have come to be used with a view to achieving a further reduction in fuel cost, and this exposes metallic components to a more corrosive environment. However, the aforesaid conventional Ni-50% Cr and MCrAlY materials fail to provide sufficient corrosion resistance and thereby function as a protective coating satisfactorily, so that the gas turbine shows a reduction in performance.
Under such circumstances, there is a demand for a spray coating powder material which can yield a sprayed coating having more excellent corrosion resistance and thermal shock resistance at high temperatures than those formed from conventional materials such as Ni-50% Cr and MCrAlY materials.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a spray coating powder material which, when applied to gas turbines using a crude low-quality fuel oil as fuel, has sufficiently higher corrosion resistance to sulfur, vanadium, sodium and other substances that accelerate corrosion in a high-temperature service environment, than conventional materials such as Ni-50 Cr and MCrAlY materials, as well as high-temperature components coated therewith.
The present invention has been made for the purpose of accomplishing the above-described object, and its subject matter includes a spray coating powder material comprising, on a weight basis, greater than 45% and up to 60% of chromium, 5 to 15% of aluminum, 0.5 to 10% of zirconium, and the balance comprising cobalt or iron, or both, and incidental impurities, as well as high-temperature components coated therewith. This material can yield a sprayed coating having high corrosion resistance to sulfur, vanadium, sodium and other substances that accelerate corrosion in a high-temperature service environment.
Thus, the present invention makes it possible to obtain a spray coating powder material having excellent corrosion resistance at high temperatures and excellent corrosion resistance to sulfur, vanadium and sodium, as well as high-temperature components coated therewith.
REFERENCES:
patent: 4101713 (1978-07-01), Hirsch et al.
patent: 5116690 (1992-05-01), Brindley et al.
patent: 0 688 885 (1995-12-01), None
patent: 10102227 (1998-04-01), None
Koji: “Powder Material For Thermal Spraying Excellent In High Temperature Corrosion Resistance”; Patent Abstracts of Japan; Publication No. 10 102227; Publication Date: Apr. 21, 1998 vol. 098, No. 009; (Jul. 31, 1998).
Fujimoto Koji
Koshiro Ikumasa
Shige Takashi
Takahashi Koji
Yonezawa Toshio
Foley & Lardner
Jenkins Daniel J.
Mitsubishi Heavy Industries Ltd.
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