Patent Application
20140205490
The present invention is directed to alloys and turbine components containing alloys. More specifically, the present invention is directed to nickel-based alloys.
Gas turbine components are subjected to both thermally, mechanically, and chemically hostile environments. For example, in the compressor portion of a gas turbine, atmospheric air is compressed, for example, to 10-25 times atmospheric pressure, and adiabatically heated, for example, to 800°-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, for example, 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 the fan and compressor of the turbine, and the exhaust system, where the gases provide sufficient energy to rotate a generator rotor to produce electricity. To improve the efficiency of operation of the turbine, combustion temperatures have been raised. To handle such higher temperatures, it is desirable to improve the properties of materials within such components.
Many alloys used in these environments include cobalt. One known alloy having cobalt at a relatively high concentration has a composition, by weight, of between about 15% and about 20% cobalt, between about 10% and 19% chromium, between about 2.5% and 3.4% aluminum, less than about 0.5% tantalum, less than about 1.0% molybdenum, less than about 0.06% zirconium, less than about 0.04% boron, between about 1.1% and about 1.5% niobium, between about 3.0% and 3.9% titanium, up to about 3% tungsten, between about 0.03% and 0.07% carbon, and a balance of nickel. Another known alloy having cobalt at relatively high concentration has a composition, by weight, of about between about 0.08% and 0.12% carbon, between about 22.2% and 22.8% chromium, about 0.10% manganese, about 0.25% silicon, between about 18.5% and 19.5% cobalt, between about 1.8% and 2.2% tungsten, about 2.3% titanium, about 1.2% aluminum, about 1.0% tantalum, about 0.8% niobium, about 0.05% zirconium, about 0.008% boron, and a balance of nickel. Another known alloy has a composition, by weight, of about 22.5% chromium, about 19% cobalt, about 2% tungsten, about 1.35% niobium, about 2.3% titanium, about 1.2% aluminum, about 0.1% carbon, about 0.01% zirconium, about 0.01% boron, and a balance of nickel. Another alloy has a composition, by weight, of about 22.5% chromium, about 19% cobalt, about 2% tungsten, about 1.35% niobium, about 2.3% titanium, about 1.7% aluminum, about 0.1% carbon, about 0.01% zirconium, about 0.01% boron and a balance of nickel.
In general, the above alloys have desirable mechanical properties, oxidation-resistance properties, and hot corrosion properties. However, using cobalt at these high concentrations can be undesirable because cobalt has been subject to substantial price fluctuations, limited availability, and often comes from regions having geopolitical instability. Prior attempts to reduce cobalt have been unsuccessful in maintaining these properties, especially creep strength.
A nickel-based alloy and a turbine component containing a nickel-based alloy that do not suffer from one or more of the above drawbacks would be desirable in the art.
In an exemplary embodiment, a nickel-based alloy includes, by weight, between about 8% and about 11% cobalt, up to about 3% niobium, up to about 3% titanium, up to about 2.3% aluminum, up to about 3% tungsten, up to about 25% chromium, up to about 0.1% carbon, up to about 0.01% boron, and a balance nickel.
In another exemplary embodiment, a nickel-based alloy includes, by weight, between about 1% and about 3% niobium, between about 1% and about 3% titanium, between about 2.1% and about 2.5% aluminum, up to about 3% tungsten, up to about 11% cobalt, up to about 25% chromium, up to about 0.1% carbon, up to about 0.01% boron, and a balance nickel.
In another exemplary embodiment, a turbine component includes one or both of a first nickel-based alloy comprising between about 8% and about 11% cobalt, up to about 3% niobium, up to about 3% titanium, up to about 2.3% aluminum, up to about 3% tungsten, up to about 25% chromium, up to about 0.1% carbon, up to about 0.01% boron, and a balance nickel and a second nickel-based alloy comprising between about 1% and about 3% niobium, between about 1% and about 3% titanium, between about 2.1% and about 2.5% aluminum, up to about 3% tungsten, up to about 11% cobalt, up to about 25% chromium, up to about 0.1% carbon, up to about 0.01% boron, and a balance nickel.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, which illustrates, by way of example, the principles of the invention.
Provided is an exemplary nickel-based alloy and a turbine component containing a nickel-based alloy. Embodiments of the present disclosure have desirable mechanical properties, oxidation-resistance properties, hot corrosion properties, creep strength, and permit resistance to price fluctuations of cobalt and/or limited availability of cobalt, or combinations thereof. In some embodiments, in comparison to the known higher cobalt alloys, the exemplary nickel-based alloy includes substantially equivalent or increased weldability, castability, structural stability, high temperature strength, hot corrosion resistance, creep strength, yield strength, ductility, phase stability, gamma prime (volume, fraction, size, and/or distribution), or combinations thereof.
The exemplary nickel-based alloy includes cobalt, chromium, tungsten, niobium, titanium, aluminum, carbon, boron, and nickel. In one embodiment, the nickel-based alloy is all or a portion of a turbine component, such as, a turbine nozzle casting, a turbine blade, a turbine bucket, a turbine dovetail, and/or any other suitable component.
The cobalt is at a concentration, by weight, of between about 8% and about 11%. In further embodiments, the cobalt is at a concentration, by weight, of between about 8% and about 10%, between about 8% and about 9.5%, at about 8%, at about 9%, at about 9.5%, at about 10%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the chromium is at a concentration, by weight, of up to about 25%, up to about 23%, up to about 22.5%, between about 20% and about 25%, between about 21% and about 23%, between about 22% and about 23%, at about 20%, at about 21%, at about 22%, at about 22.5%, at about 23%, at about 25%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the tungsten is at a concentration, by weight, between about 1% and about 3%, at about 1%, at about 2%, at about 2.5%, at about 3%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the niobium is at a concentration, by weight, between about 1% and about 3%, at about 2%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the titanium is at a concentration, by weight, between about 2% and about 3%, between about 2% and about 2.3%, between about 2.3% and about 2.5%, between about 2% and about 2.5%, at about 2.3%, at about 2.5%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the aluminum is at a concentration, by weight, of between about 2% and about 2.3%, at about 2.1%, at about 2.2%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the carbon is at a concentration, by weight, of up to about 0.1%, up to about 0.08%, between about 0.05% and about 0.15%, between about 0.05% and about 0.1%, between about 0.05% and about 0.08%, between about 0.08% and about 0.1%, at about 0.05%, at about 0.08%, at about 0.1%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the boron is at a concentration, by weight, of up to about 0.01%, up to about 0.008%, between about 0.005% and about 0.015%, between about 0.005% and about 0.01%, at about 0.005%, at about 0.008%, at about 0.01%, or any suitable combination, sub-combination, range, or sub-range thereof.
In one embodiment, the nickel-based alloy includes a balance of nickel.
In one embodiment, the nickel-based alloy includes or consists of, by weight, about 22.5% chromium, about 9.5%, cobalt, about 2% tungsten, about 2% niobium, about 2.3% titanium, about 2.3% aluminum, about 0.08% carbon, about 0.008% boron, incidental impurities, and a balance nickel.
In other embodiments, the nickel-based alloy is devoid or substantially devoid of tantalum, molybdenum, zirconium, or a combination thereof.
In one embodiment, the nickel-based alloy includes tensile strength at 1200° F. for 0.2% yield strength of at about 90 ksi.
In one embodiment, the nickel-based alloy includes tensile ductility at 1200° F. of greater than about 20%.
In one embodiment, the nickel-based alloy includes low-cycle fatigue properties (creep strength) at 1600° F. with 0.7% strain for 2 minutes of greater than about 3,500 cycles prior to crack initiation.
In one embodiment, the nickel-based alloy exhibits 2% creep under 18 ksi at 1600° F. after about 1,900 hours.
In one embodiment, the nickel-based alloy exhibits oxidation, after about 2,000 hours, at about 127 microns.
In one embodiment, the nickel-based alloy includes corrosion-resistance, under conditions of 1,700° F. in 5 ppm salt with 0.4% sulfur. For example, in one embodiment, at about 600 hours, maximum penetration into the nickel-based alloy is at about 1.85 mils. In one embodiment, at about 1,000 hours, maximum penetration into the nickel-based alloy is at about 4.56 mils. In one embodiment, at about 1,400 hours, maximum penetration into the nickel-based alloy is at about 7.46 mils.
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.
