Patent Application
20120213626
The present invention is directed to manufactured components and processes of forming manufactured components. More specifically, the present invention relates to explosion-welded components and explosion welding processes.
The operating temperature within a gas turbine is both thermally and chemically hostile. Significant advances in high temperature capabilities have been achieved through the development of iron, nickel, and cobalt-based superalloys and the use of environmental coatings capable of protecting superalloys from oxidation, hot corrosion, etc., but coating systems continue to be developed to improve the performance of the materials.
In the compressor portion of a gas turbine, atmospheric air is compressed to 10-25 times atmospheric pressure, and adiabatically heated to 800° F.-1250° F. (427° C.-677° C.) in the process. This heated and compressed air is directed into a combustor, where it is mixed with fuel. The fuel is ignited, and the combustion process heats the gases to very high temperatures, in excess of 3000° F. (1650° C.). These hot gases pass through the turbine, where airfoils fixed to rotating turbine disks extract energy to drive an attached generator which produces electrical power. To improve the efficiency of operation of the turbine, combustion temperatures have been raised. Of course, as the combustion temperature is raised, steps must be taken to prevent thermal degradation of the materials forming the flow path for these hot gases of combustion.
Certain known alloys are used for components disposed along the flow path of these hot gases. Certain portions of these components must be able to withstand temperatures higher than other portions of these components. For example, certain portions may be resistant to temperatures for adiabatic heating (for example, 800° F.-1250° F.) and other portions may be further resistant to hot gases heated by the combustion processes (for example, in excess of 3000° F.). Components made entirely of alloys resistant to the highest temperature may be undesirable by being overly expensive or failing to include other properties desirable in other portions of the components. Alternatively, components made entirely of alloys resistant only to the temperature of the lower temperature portions may fail.
Generally, gas turbine shrouds are manufactured from one or more rings or cylinders. As such, manufacturing and tooling facilities are configured for manufacturing gas turbine shrouds from one or more rings or cylinders. Welding of multiple materials to form gas turbine shrouds may include techniques such as weld build-up, strip cladding, brazing, or solid state bonding. These techniques suffer from a drawback that they may be limited based upon properties of the materials (for example, crystal structures, compositions, or other suitable properties).
Explosion welding is a bonding technique that generally includes welding planar materials by an explosive force and results in a microstructure differing from other weld techniques. Explosion welding permits metals to be bonded that are otherwise generally incompatible. However, explosion welding processes have been limited to simple shapes and geometries. Therefore, current explosion welding techniques have been unable to bond structures in gas turbine shrouds.
An explosion-welded turbine shroud, an explosion-welded component, and an explosion-welding process that do not suffer from one or more of the above drawbacks would be desirable in the art.
According to an exemplary embodiment, a gas turbine shroud includes a first alloy explosion welded to a second alloy. The first alloy forms at least a portion of a hot gas path of the gas turbine shroud.
According to another exemplary embodiment, a gas turbine shroud includes an expansion region and a first alloy explosion welded to a second alloy. The expansion region of the gas turbine shroud includes the first alloy.
According to another exemplary embodiment, a process of forming an explosion-welded gas turbine shroud includes explosion welding a first alloy to a second alloy. The first alloy forms at least a portion of a hot gas path of the gas turbine shroud.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
Provided is an explosion-welded gas turbine shroud, a non-planar explosion-welded component, and a process of forming a non-planar explosion-welded component. Embodiments of the present disclosure permit components to be used in thermally and chemically hostile environments, permit components to be resistant to oxidation and/or hot corrosion, permit the overall material cost of components to be reduced in comparison to single alloy components, permit different portions of components to have different properties (for example, heat resistant properties), permit non-planar components to have properties available through explosion welding, permit materials having otherwise incompatible properties to be bonded (for example, otherwise incompatible crystal structures and/or compositions), and combinations thereof.
The shroud 100 includes a first alloy 102 and a second alloy 106. The first alloy 102 is positioned along the substantially planar member 109 as a cladding layer 104 and the second alloy 106 forms the substantially planar member 109 and is a backing layer 108. The cladding layer 104 is resistant to heat above a first temperature (for example, about 1000° F., about 1250° F., about 1500° F., about 2000° F., or about 3000° F.). The backing layer 108 is resistant to heat above a second temperature (for example, between 800° F. and 1250° F., about 800° F., about 1000° F., about 1250° F., about 1500° F., or about 2000° F.). In one embodiment, the first temperature is substantially higher than the second temperature. In a further embodiment, the second alloy 106 is unsuitable for being exposed to the first temperature.
The first alloy 102 is an austenitic alloy, such as austenitic stainless steel or austenitic manganese steel. The first alloy 102 is any suitable cladding material. Suitable cladding materials include, but are not limited to, stainless steel alloys, aluminum alloys, tantalum alloys, nickel alloys, copper alloys, titanium alloys, zirconium alloys, and combinations thereof In one embodiment, the second alloy 106 is an austenitic alloy. In one embodiment, the second alloy 106 is a ferritic alloy such as ferritic stainless steel. The second alloy 106 is any suitable backing material. Suitable backing materials include, but are not limited to, carbon steel, chromium-molybdenum alloy steel, forgings, stainless steel, or combinations thereof.
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In one embodiment of the process, the forming of the shroud 100 or any other suitable component includes positioning a first portion of the shroud 100 and positioning a second portion of the shroud 100. The first portion includes the first alloy 102 (for example, the cladding layer 104) and the second portion includes the second alloy 106 (for example, the substantially planar member 109 or the backing layer 108). The first portion and the second portion are explosion welded together to form the preform 300. The preform 300 is then machined, deformed, further welded, or otherwise processed to remove excess material 302 and form the desired features of the shroud 100. In an alternative embodiment where the preform 300 does not include the ribs 107, the ribs 107 are formed on the preform 300 after the explosion welding by removing material through machining or by bonding the ribs 107 to the substantially planar member 109.
The explosion welding of the first alloy 102 to the second alloy 106 is by ignition or initiation of detonation to direct the first alloy 102 with explosive force to contact the second alloy 106. The explosion welding is continued until a desired portion of the first alloy 102 is explosion welded to the second alloy 106. The explosion welding is performed along any suitable path. Suitable paths include, but are not limited to, a helical path for a cylindrical component (or preform), a series of paths, an S-shaped path, or combinations thereof. In embodiments including a series of paths, multiple coordinated ignitions or initiations of detonations coordinate the explosive welding (for example, concurrent, sequential, or otherwise controlled detonations).
During the explosion welding process, the ignitions or detonations are performed at predetermined conditions. In one embodiment, parameters include a predetermined pressure (for example, between about 1 GPa and about 10 GPa, about 5 GPa, or about 10 GPa), a predetermined detonation rate (for example, between about 1500 m/s and 4000 m/s, between about 1500 m/s and about 2000 m/s, between about 3500 m/s and about 4000 m/s, at about 1500 m/s, at about 2000 m/s, at about 3500 m/s, or at about 4000 m/s), a predetermined impact angle (for example, between about 3° and about 30°, between about 3° and about 5°, between about 25° and about 30°, at about 3°, at about 5°, at about 25°, or at about)30°, a predetermined collision velocity (for example, between about 225 m/s and about 550 m/s, between about 225 m/s and about 250 m/s, between about 500 m/s and about 550 m/s, at about 225 m/s, at about 250 m/s, at about 500 m/s, or at about 550 m/s), or combinations thereof.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
