This disclosure relates to nickel based superalloys. In particular this disclosure relates to superalloys used in high temperature gas turbine engine components such as turbine discs and compressor discs.
In operation, the turbine discs encounter different operating conditions radially from the center or hub portion to the exterior or rim portion. The rim is hotter than the hub and, in general, all of the operating temperatures are higher for more advanced engines. The stress conditions also vary radially, with lower stresses at the rim and higher stresses at the hub. As a result of different operating conditions, the material at the rim of the disc must exhibit good high temperature creep and stress rupture resistance as well as high temperature strength and hold time fatigue crack growth resistance. The hub region of the disc must exhibit high tensile strength at more moderate temperatures and resistance to low cycle fatigue crack growth. In the most common designs, the entire turbine disc is made of a single forged and heat treated piece of material. The alloy used in the disc is therefore selected to meet all of the material requirements discussed above.
Exotic materials have been developed to address the demands of turbine disc use. U.S. Pat. No. 6,521,175 (the '175 patent) discloses an advanced nickel based superalloy for powder metallurgical (PM) manufacture of turbine discs. The disclosure of the '175 patent is incorporated by reference herein in its entirety. The '175 patent discloses disc alloys optimized for short time engine cycles, with disc temperatures approaching temperatures of about 1500° F. (816° C.). U.S. Pat. App. Pub. 2010/0008790 discloses a nickel based disc alloy having a relatively high concentration of tantalum coexisting with a relatively high concentration of one or more other components. Other disc alloys are disclosed in U.S. Pat. No. 5,104,614, U.S. Pat. No. 5,662,749, U.S. Pat. No. 6,908,519, EP 1,201,777, and EP 1,195,446.
It is advantageous in some instances to use different materials for a disc hub and rim to maximize performance.
A nickel braze alloy may include less than about 2.0 wt. % aluminum, about 18.0-23.0 wt. % cobalt, about 12.0-15.0 wt. % chromium, about 3.8-4.5 wt. % molybdenum, about 0.8-1.5 wt. % niobium, about 1.8-3.0 wt. % tantalum, less than about 2.0 wt. % titanium, about 2.0-3.5 wt. % tungsten, about 0.8-1.2 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
In an embodiment a method of joining a first superalloy component with a first joining surface to a second superalloy component with a second joining surface along the matching joining surfaces includes forming an assembly wherein the first component and the second component are positioned such that the first and second joining surfaces face each other with a layer of transient liquid phase brazing alloy therebetween having with the following composition: less than about 2.0 wt. % aluminum, about 18.0-23.0 wt. % cobalt, about 12.0-15.0 wt. % chromium, about 3.8-4.5 wt. % molybdenum, about 0.8-1.5 wt. % niobium, about 1.8-3.0 wt. % tantalum, less than about 2.0 wt. % titanium, about 2.0-3.5 wt. % tungsten, about 0.8-1.2 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities on the first and/or second joining surfaces. The assembly is then heated to a predetermined temperature such that the transient liquid phase brazing alloy melts and the first and second superalloy joining surfaces do not melt. The assembly is then held at the predetermined temperature for a predetermined amount of time wherein the brazing alloy isothermally solidifies and forms a metallurgical bond between the first and second superalloy components.
The disc 22 may be formed by a powder metallurgical forging process (e.g., as indicated in U.S. Pat. No. 6,521,175).
The quench for the heat treatment may also form strengthening precipitates of a desired distribution of sizes and desired volume percentages. Subsequent heat treatments are used to modify these distributions to produce the requisite mechanical properties of the manufactured forging. Increased grain size is associated with good high temperature creep resistance and decreased rate of crack growth during the service of the manufactured forging. The heat treated forging is then subject to machining of the final profile and the slots.
The alloy series described in the '175 alloy series patent forms a disc product with exceptional bore strength. Recent alloy series described in commonly owned U.S. Pat. App. Pubs. 2013/0209265 (the '265 alloy series) and 2013/02109266 (the '266 alloy series), which are incorporated herein by reference in their entirety, disclose alloys with improved high temperature creep and rupture lives over prior art alloys. Hybrid disc structures with '175 alloy series bores and '265 and/or '266 alloy series rim structures can provide improved performance over single-material disc structures.
The '175 alloy series bore composition comprises about 2.6-4.8 wt. % aluminum, about 16.0-22.4 wt. % cobalt, about 6.6-14.3 wt. % chromium, about 1.9-3.9 wt. % molybdenum, about 0.9-3.0 wt. % niobium, about 1.4-3.5 wt. % tantalum, about 2.4-4.6 wt. % titanium, about 1.9-4.0 wt. % tungsten, about 0.02-0.10 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.10 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The '265 alloy series rim composition comprises about 3.10-3.75 wt. % aluminum, about 20.0-22.0 wt. % cobalt, about 9.5-11.25 wt. % chromium, about 2.8-4.2 wt. % molybdenum, about 1.6-2.4 wt. % niobium, about 4.2-6.1 wt. % tantalum, about 2.6-3.5 wt. % titanium, about 1.8-2.5 wt. % tungsten, about 0.02-0.09 wt. % boron, about 0.02-0.09 wt. % carbon, about 0.04-0.09 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The '266 alloy series rim composition comprises about 3.2-4.1 wt. % aluminum, about 20.0-22.0 wt. % cobalt, about 8-10.5 wt. % chromium, about 2.8-3.1 wt. % molybdenum, about 1.6-2.4 wt. % niobium, about 2.5-7.3 wt. % tantalum, about 2.6-3.6 wt. % titanium, about 2.8-3.3 wt. % tungsten, about 0.02-0.09 wt. % boron, about 0.02-0.09 wt. % carbon, about 0.04-0.09 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
Advanced TLP braze alloys to join '175 hub alloys to '265 and/or '266 rim alloys to form hybrid disc structure 40 are the subject of the present disclosure. Prior art commercially available TLP braze alloys for superalloys are eutectic compositions of nickel, chromium, and boron, a melting point depressant. During brazing, the structure is heated to a fixed temperature exceeding the melting point of the braze alloy but not above the melting points of the two structures being joined. Maintaining the brazing temperature at a fixed temperature allows boron to defuse away from the joint and into the surrounding structure. As the braze alloy loses boron, the melting temperature increases until the braze alloy isothermally solidifies and forms a metallurgical bond.
Prior art brazing alloys could result in a weak bond as a result of the limited diffusion of solid solution strengtheners such as niobium, titanium and tungsten and the limited formation of gamma prime as a result of limited mean free path of diffusion of large atoms such as aluminum, titanium, tantalum, and niobium.
In an embodiment of the invention, a preferred brazing alloy composition for brazing superalloy disc structures includes less than about 2.0 wt. % aluminum, about 18.0-23.0 wt. % cobalt, about 12.0-15.0 wt. % chromium, about 3.8-4.5 wt. % molybdenum, about 0.8-1.5 wt. % niobium, about 1.8-3.0 wt. % tantalum, less than about 2.0 wt. % titanium, about 2.0-3.5 wt. % tungsten, about 0.8-1.2 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
A preferred brazing alloy within this range has a composition that includes less than 1.8 wt. % aluminum, about 20.0-22.0 wt. % cobalt, about 13.0-14.5 wt. % chromium, about 3.9-4.3 wt. % molybdenum, about 0.9-1.0 wt. % niobium, about 2.0-2.5 wt. % tantalum, less than about 1.95 wt. % titanium, about 2.1-3.0 wt. % tungsten, about 0.9-1.1 wt. % boron, about 0.04-0.06 wt. % carbon, about 0.04-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
A particularly preferred braze alloy within this range has a composition that includes about 21.90 wt. % cobalt, about 14.00 wt. % chromium, about 4.10 wt. % molybdenum, about 0.97 wt. % niobium, about 2.58 wt. % tantalum, about 2.26 wt. % tungsten, about 1.00 wt. % boron, about 0.05 wt. % carbon, about 0.05 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
Another particularly preferred braze alloy within this range has a composition that includes about 1.73 wt. % aluminum, about 21.10 wt. % cobalt, about 13.48 wt. % chromium, about 3.94 wt. % molybdenum, about 0.93 wt. % niobium, about 2.45 wt. % tantalum, about 1.92 wt. % titanium, about 2.18 wt. % tungsten, about 1.00 wt. % boron, about 0.05 wt. % carbon, about 0.05 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A nickel braze alloy may include in combination less than about 2.0 wt. % aluminum, about 18.0-23.0 wt. % cobalt, about 12.0-15.0 wt. % chromium, about 3.8-4.5 wt. % molybdenum, about 0.8-1.5 wt. % niobium, about 1.8-3.0 wt. % tantalum, less than about 2.0 wt. % titanium, about 2.0-3.5 wt. % tungsten, about 0.8-1.2 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.06 wt. % zirconium and a balance of nickel and minor amounts of impurities.
The alloy of the preceding paragraph can optionally included, additionally and/or alternatively any, one or more of the following features, configurations and/or additional components:
The composition may include less than about 1.8 wt. % aluminum, about 20.0-22.0 wt. % cobalt, about 13.0-14.5 wt. % chromium, about 3.9-4.3 wt. % molybdenum, about 0.9-1.0 wt. % niobium, about 2.0-2.5 wt. % tantalum, less than about 1.95 wt. % titanium, about 2.1-3.0 wt. % tungsten, about 0.9-1.1 wt. % boron, about 0.04-0.06 wt. % carbon, about 0.04-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The composition may include about 21.90 wt. % cobalt, about 14.00 wt. % chromium, about 4.10 wt. % molybdenum, about 0.97 wt. % niobium, about 2.58 wt. % tantalum, about 2.26 wt. % tungsten about 1.00 wt. % boron, about 0.05 wt. % carbon, about 0.05 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The composition may include about 1.73 wt. % aluminum, about 21.10 wt. % cobalt, about 13.48 wt. % chromium, about 3.94 wt. % molybdenum, about 0.93 wt. % niobium, about 2.48 wt. % tantalum, about 1.92 wt. % titanium, about 2.18 wt. % tungsten, about 1.00 wt. % boron, about 0.05 wt. % carbon, about 0.05 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The alloy may be a foil, tape, cloth, powder, or slurry.
The alloy may be a foil.
The foil may have a thickness of from about 1.0 mils (2.54 microns) to about 1.5 mils (38.1 microns).
A method of joining a first superalloy component with a first joining surface to a second superalloy component with a second joining surface along the matching joining surfaces may include: forming an assembly wherein the first component and the second component are positioned such that the first and second joining surfaces are facing each other with a layer of transient liquid phase brazing alloy therebetween having the following composition: less than about 2.0 wt. % aluminum, about 18.0-23.0 wt. % cobalt, about 12.0-15.0 wt. % chromium, about 3.8-4.5 wt. % molybdenum, about 0.8-1.5 wt. % niobium, about 1.8-3.0 wt. % tantalum, less than about 2.0 wt. % titanium, about 2.0-3.5 wt. % tungsten, about 0.8-1.2 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities on the first and/or second joining surfaces; heating the assembly to a predetermined temperature such that the transient liquid phase brazing alloy melts and the first and second superalloy joining surfaces do not melt; and holding the assembly at the predetermined temperature for a predetermined amount of time wherein the brazing alloy isothermally solidifies and forms a metallurgical bond between the first and second superalloy components.
The method of the preceding paragraph can optionally include, additionally and/or alternatively any, one or more of the following features, configurations and/or additional components:
The transient liquid phase brazing alloy may have the following composition: less than about 1.8 wt. % aluminum, about 20.-22.0 wt. % cobalt, about 13.0-14.5 wt. % chromium, about 3.9-4.3 wt. % molybdenum, about 0.9-1.0 wt. % niobium, about 2.0-2.5 wt. % tantalum, less than about 1.95 wt. % titanium, about 2.1-3.0 wt. % tungsten, about 0.9-1.7 wt. % boron, about 0.04-0.06 wt. % carbon, about 0.04-0.06 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The transient liquid phase brazing alloy may have the following composition: about 21.90 wt. % cobalt, about 14.00 wt. % chromium, about 4.10 wt. % molybdenum, about 0.97 wt. % niobium, about 2.58 wt. % tantalum, about 2.26 wt. % tungsten, about 1.00 wt. % boron, about 0.05 wt. % carbon, about 0.05 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The transient liquid phase brazing alloy may have the following composition: about 1.73 wt. % aluminum, about 21.10 wt. % cobalt, about 13.48 wt. % chromium, about 3.94 wt. % molybdenum, about 0.93 wt. % niobium, about 2.48 wt. % tantalum, about 1.92 wt. % titanium, about 2.18 wt. % tungsten, about 1.00 wt. % boron, about 0.05 wt. % carbon, about 0.05 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The transient liquid phase brazing alloy may be a foil, tape, cloth, powder, or slurry.
The transient liquid phase brazing alloy may be a foil.
The foil may have a thickness of from about 1.0 mils (25.4 microns) to about 1.5 mils (38.1 microns).
The first component may be an alloy with the following composition: about 2.6-4.8 wt. % aluminum, about 16.0-22.4 wt. % cobalt, about 6.6-14-3 wt. % chromium, about 1.9-3.9 wt. % molybdenum, about 0.9-3.0 wt. % niobium, about 1.4-3.5 wt. % tantalum, about 2.4-4.6 wt. % titanium, about 1.9-4.0 wt. % tungsten, about 0.02-0.10 wt. % boron, about 0.02-0.10 wt. % carbon, about 0.03-0.10 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The second component may be an alloy with the following composition: about 3.10-3.75 wt. % aluminum, about 20.0-22.0 wt. % cobalt, about 9.5-11.25 wt. % chromium, 2.8-4.2 wt. % molybdenum, about 1.6-2.4 wt. % niobium, about 4.2-6.1 wt. % tantalum, about 2.6-3.5 wt. % titanium, about 1.8-2.5 wt. % tungsten, about 0.02-0.09 wt. % boron, about 0.02-0.09 wt. % carbon, about 0.04-0.09 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
The second compound may be an alloy with the following composition: about 3.2-4.1 wt. % aluminum, about 20.0-22.0 wt. % cobalt, about 8-10.5 wt. % chromium, about 2.8-3.1 wt. % molybdenum, about 1.6-2.4 wt. % niobium, about 2.5-7.3 wt. % tantalum, about 2.6-3.6 wt. % titanium, about 2.8-3.3 wt. % tungsten, about 0.02-0.09 wt. % boron, about 0.02-0.09 wt. % carbon, about 0.04-0.09 wt. % zirconium, and a balance of nickel and minor amounts of impurities.
While the invention has been described with reference to an exemplary embodiment(s), 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(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
This invention was made with government support under Contract No. FA8650-14-2-5209 awarded by United States Air Force. The government has certain rights in the invention.