Stock material or miscellaneous articles – All metal or with adjacent metals – Having metal particles
Reexamination Certificate
2000-07-06
2001-12-18
Dunn, Tom (Department: 1725)
Stock material or miscellaneous articles
All metal or with adjacent metals
Having metal particles
C428S615000, C029S889100, C228S119000, C228S245000, C415S012000
Reexamination Certificate
active
06331361
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the repair and manufacture of components, preferably turbo-machinery components, by the insertion of directionally solidified or single crystal sections into parts comprised mostly of equiaxed cast or wrought alloys.
Thermal mechanical fatigue, oxidation/corrosion, and creep all play a role in the overall life expectancy of components and in particular, turbo-machinery components operating at high temperatures. These mechanisms produce cracking and microstructural degradation in all areas of the component but the most severe damage usually occurs at the leading and trailing edges of vanes. The entire component is typically manufactured from a single forging or is cast. During a repair process, the most damaged areas are often replaced with new “coupon” pieces of equiaxed cast or wrought material. These coupons or inserts are usually welded into position.
SUMMARY OF THE INVENTION
Since the stresses in many of the most critical areas are unixal, the main object of the present invention is to provide a method of manufacturing and repair wherein additional strength in the direction of primary loading is obtained to improve the components' physical strength and in-service life. High temperature materials are weakest at the boundaries between the individual grains of metal. Directionally solidified castings are produced by special processes, which cause the grain to grow uniformy in a single direction. The result is a material which has greater strength in a single direction (the direction of grain orientation), because there are no grain boundaries normal to the applied loading direction. Single crystal materials do not have grain boundaries and have improved strength in multi-axial loaded conditions.
Directionally solidified and single crystal materials have been used for years in rotating hot section blades to increase the creep and thermal mechanical fatigue properties of those parts. In recent years, this same technology has been successfully applied to materials for whole stationary components. Both of these casting processes are limited by the size of the product. It becomes increasingly difficult to maintain the proper structure and grain orientation as the casting size increases. Another object of the present invention is to provide a composite component manufactured primarily from a forging or conventional casting with one or more directionally solidified or single crystal inserts in critical areas to improve the overall performance of the part. A further object is the modification and improvement of established product designs and the insertion or replacement of critical areas of service exposed, equiaxed components with directionally solidified or single crystal materials to increase the remaining life expectancy.
These and other objects of the invention are achieved in accordance with the invention by a method form manufacturing, comprising the steps of providing a component composed of equiaxed cast or wrought alloys and joining at least one section composed of directionally solidified or single crystal material to the component. The at least one section can be joined by welding or other joining process. In one embodiment, the component is composed of equiaxed cast or wrought alloys and is provided without the at least one section. The component can be a gas turbine vane without leading and trailing edge sections thereof and wherein the at least one section comprises the leading and trailing edge sections of the gas turbine vane with respect to a direction of the gas therethrough. In that embodiment, the directionally solidified or single crystal material in the leading and trailing edge sections preferably have a grain orientation normal to the direction of gas.
Another embodiment of the invention is a method for repairing a component, comprising the steps of providing a component composed of equiaxed cast or wrought alloys, removing at least one section of the component, providing at least one new section composed of directionally solidified or single crystal material and joining the at least one new section to the component. Where the component is a gas turbine vane, the at least one section preferably comprises leading and trailing edge sections of the gas turbine vane with respect to a direction of gas therethrough. In that embodiment, the directionally solidified or single crystal material in the leading and trailing edge sections preferably have a grain orientation normal to the direction of the gas.
A further embodiment of the invention is an article of manufacture comprising a section composed of equiaxed cast or wrought alloys and at least one section composed of directionally solidified or single crystal material joined thereto.
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Esch Hans van
Greaves Wayne
Clifford Chance Rogers & Wells LLP
Dunn Tom
Hickham Industries, Inc.
Schaefer, Esq. Ira J.
Stoner Kiley
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