Patent Application
20070081912
The present invention relates to turbine disks and, more particularly, to turbine disks that are multiple microstructure components.
During operation of a gas turbine engine, a disk that supports a plurality of turbine blades typically rotates at high speeds in a high temperature environment. In many cases, a hub portion of the disk is exposed to temperatures of about 1000° F., while a rim portion of the disk is exposed to higher temperatures, such as about 1500° F. or higher. Because of the differences in operating conditions, the hub and rim are preferably formed of alloys having different properties. For example, hubs have been formed from alloys having high tensile strength and high resistance to low cycle fatigue, while rims have been formed from alloys having high stress rupture and creep resistance.
Several techniques currently exist for constructing dual alloy turbine wheel hubs. However, each suffers from certain drawbacks. For example, one technique includes metallurgically bonding an inner hub preform to a rim preform and isothermally forging the two together. Although such a technique yields acceptable disks, only one disk may be produced from the two preforms. Another technique involves forming a disk preform having a first grain structure and using specialized equipment to heat an outer periphery of the disk structure to obtain a second grain microstructure. However, such equipment is relatively expensive and thus, the technique is costly to implement. Still another technique uses a conventionally cast ingot that is extruded or hot isostatically pressed to yield an ingot having an inner and an outer region, each having a different grain microstructure. However, the boundary, location, and shape of the first and second regions may be imprecise.
Thus, there is a need for a method for forming a dual alloy turbine wheel hub that is relatively inexpensive and that utilizes conventional equipment. Additionally, there is a need for a method that can be used to form more than one turbine wheel hub.
The present invention provides methods for manufacturing turbine disks each having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the method employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature.
In one embodiment, and by way of example only, the method includes the steps of forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having a microstructure that is less coarse than the second microstructure, and exposing the ingot to a temperature between the first and second gamma prime solvus temperatures while forming the ingot into a plurality of turbine disks to transform the microstructure of the outer section into the second microstructure.
In another embodiment, and by way of example only, a method is provided for manufacturing a turbine disk having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the method employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature. The method comprises the steps of forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having the second microstructure, and exposing the ingot to a temperature below the first gamma prime solvus temperature while forming the ingot into a plurality of turbine disks.
Other independent features and advantages of the preferred methods will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Turning now to
To form the turbine disk 100, generally, first an ingot 200, shown in
The ingot 200 and turbine disk 100 may be formed using any one of the following methods. It will be appreciated that in each of the following methods, two powder alloys are used. Each powder alloy includes a gamma phase component and a gamma prime phase component, where the gamma phase component is a metal matrix and the gamma prime phase component is a precipitate that is held in solution within the metal matrix when the first powder alloy phase changes into a solid. Each gamma prime phase component preferably has a different temperature at which it enters into solution, and heat treatment above that temperature results in grain growth. In the methods described below, a gamma prime solvus temperature TA of the first powder alloy is greater than a gamma prime solvus temperature TB of the second powder alloy.
It will be appreciated that any one of numerous suitable powder alloys conventionally used in the formation of turbine disks may be employed. For example, two chemical variations of a single alloy, such as Alloy 10 produced by Honeywell, Inc. of Morristown, N.J. may be used. In this embodiment, a first variation may include 18.5 wt. % Cr, while a second variation may includes 19.5 wt % Cr. Other suitable powder alloys that include, but are not limited to Rene 95, low carbon Astroloy, and Alloy 720 may alternatively be used.
One exemplary method 300, shown in
As briefly mentioned above, the first powder alloy is deposited into a first volume, step 302. Preferably, the first volume is configured to have the shape of the inner section 202 of the ingot 200 and is contained in a suitably shaped space of a container. Thus, for example, the container may be a hollow cylinder. The container is preferably constructed of any one of numerous suitable materials capable of withstanding temperatures of at least 2000° F. to allow the first powder alloy to solidify into a desired shape.
After deposition, the first powder alloy is then pressurized at a temperature below its gamma prime solvus temperature, TA, step 304. Preferably, the powder alloy is pressurized at a pressure of between about 10 ksi and about 30 ksi. Consequently, the first powder alloy transforms into the first component having a fine grain microstructure, where each grain size is between about 5 microns and about 10 microns. In an embodiment in which the first powder alloy is deposited into a hollow cylinder, the first section is formed into a solid rod.
The second powder alloy is deposited into a second volume, step 306. In one exemplary embodiment, the second volume is contained in a container shaped similarly to the outer section 204 of the ingot 200. In this regard, the container may be an annular tube having an outer annular space separated from an inner space sized to receive the first component. In another exemplary embodiment, the container has any shape.
The second powder alloy is pressurized at a temperature above its gamma prime solvus temperature, TB, step 308, to form the second component. Preferably, the powder alloy is pressurized at a pressure of between about 10 ksi and about 30 ksi. As a result, the second powder alloy transforms into a solid having a coarse grain microstructure with grain sizes of between about 15 microns and about 30 microns.
After the first and second components are formed, they are containerized in a single container, step 310. In one embodiment of method 300, the first and second components are machined into appropriate shapes before containerization. If needed, the first component is machined into the shape of the ingot inner section 202, for example, a rod, while the second section is formed into the shape of the ingot outer section 204, for example, an annular cylinder having a suitably sized rod-shaped shape therein. During containerization, the first component is nested in the space of the second component.
Next, the first and second components are pressurized at a temperature below TA, step 312. During this step, the first and second components are subjected to a pressure of between about 10 ksi and about 30 ksi and are metallurgically bond to each other to form the ingot 200. While maintaining a temperature below TA, the ingot 200 is then processed to form the turbine disk 100, step 314. Specifically, the ingot 200 is sliced, machined, and/or heat-treated.
It will be appreciated that although these steps 302, 304, 306, 308, 310, 312, 314 are discussed above in a specific sequence, they may be performed in any other suitable sequence.
Another exemplary method 400 for forming the turbine disk 100, is depicted in
In one exemplary embodiment of method 400, the powder alloys in the container are pressurized at a temperature below TB, step 404. Preferably, the powder alloys are pressurized at a pressure of between about 10 ksi and about 30 ksi. As a result, the first and second powder alloys solidify and metallurgically bond together to form the inner and outer sections 202, 204 of the ingot 200, respectively. The inner and outer sections 202, 204 each have a fine-grained microstructure. It will be appreciated that the pressurization of the powder alloys may be performed in any one of numerous manners. For example, the powder alloys may be extruded from a container having a first diameter through a container having a second, smaller diameter, step 406. In either case, the ingot 200 is further processed, for example, sliced, machined, and/or heat treated to form the turbine disk 100 at a temperature that is between TA and TB, step 408. Consequently, grain growth occurs in the outer section 204, but does not occur in the inner section 202 to thereby yield a coarse-grained microstructure and fine-grained microstructure, respectively.
In another exemplary embodiment of the method 400, the powder alloys in the container are pressurized at a temperature that is between TA and TB, step 410. Preferably, the powder alloys are pressurized at a pressure of between about 10 ksi and about 30 ksi. The first and second powder alloys solidify to form the inner and outer sections 202, 204 of the ingot 200, respectively, where the inner section 202 has a fine-grained microstructure and the outer section 204 has a coarse-grained microstructure. Additionally, the inner and outer sections 202, 204 are metallurgically bonded to form the ingot 200. Next, the ingot 200 is further processed, for example, sliced, machined, and/or heat treated, step 412. Preferably, the processing is performed at a temperature that is below TA to maintain the fine-grained microstructure of the inner section 202 and the coarse-grained microstructure of the outer section 204.
In one exemplary embodiment of method 500, the containerized first component and second powder alloy are pressurized at a temperature below TB, step 510. Preferably, pressurization occurs at between about 10 ksi and about 30 ksi. As a result, the second powder alloy solidifies and forms the second component. The second component, which surrounds the first component, metallurgically bonds thereto to form the ingot 200. Additionally, the second component transforms into a fine-grained microstructure. The ingot 200 is then further processed into the turbine disk 100 at a temperature between TA and TB, step 512. Consequently, the outer section 204 experiences grain growth to form a coarse-grained microstructure, while the inner section 202 maintains a fine-grained structure.
In an alternate embodiment of method 500, the containerized first component and second powder alloy are pressurized at a temperature between TA and TB, step 514, after the containerization step 508. Preferably, pressurization occur at between about 10 ksi and about 30 ksi. During this step, the second powder alloy solidifies and forms the second component, and the first and second components metallurgically bond to form the ingot 200 having the inner and outer sections 202, 204. In this embodiment, the inner section 202 has a fine-grained microstructure, while the outer section 204 has a coarse-grained microstructure. The ingot 200 is then processed into the turbine disk 100 at a temperature that is below TA, step 516, so that the microstructures of the inner and outer sections 202, 204 are maintained.
In one exemplary embodiment of method 600, the containerized second component and first powder alloy are pressurized at a temperature between TA and TB, step 610. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. As a result, the first powder alloy solidifies and forms the first component having a coarse-grained microstructure. Additionally, the second component maintains a fine-grained microstructure. Moreover, the first and second components metallurgically bond to each other and form the ingot 200. The ingot 200 is then processed, for example, sliced, machined, and/or heat-treated, at a temperature that is below TB to form the turbine disk 100, step 612.
In an alternate embodiment of method 600, after step 608, the containerized second component and first powder alloy are pressurized at a temperature below TB, step 614. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. In this case, the first powder alloy phase changes into a solid first component and metallurgically bonds to the second component to form the ingot 200. However, both the ingot inner and outer sections 202, 204 have fine-grained microstructures. After step 614, the ingot 200 is processed at a temperature of between TA and TB, step 616, and as a result, the inner section 202 maintains a fine-grained microstructure, while the outer section 204 experiences grain growth and forms a coarse-grained microstructure.
After step 706, the second component and first powder alloy are containerized, step 708. Preferably, the second component is positioned in a suitable container and the first powder alloy is deposited into the hollow section of the second component. The containerized second component and first powder alloy are pressurized at a temperature between TA and TB, step 710. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. In this regard, the first powder alloy solidifies to form the first component and the first and second components metallurgically bond to each other to form the ingot 200. The pressurization step causes the grains in the ingot outer section 204 to grow into a coarse-grained microstructure, while the ingot inner section 202 has a fine-grained microstructure. Subsequently, the ingot 200 is further processed into the turbine disk 100 at a temperature below TA, step 712. Thus, while the ingot 200 is being sliced, machined, and/or heat-treated, the fine-grained microstructure of the inner section 202 and the coarse-grained microstructure of the outer section 204 are maintained.
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 to 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.
