Nickel-iron-base alloy and process of forming a nickel-iron-base alloy   

FIELD OF THE INVENTION

The present invention is directed to alloys, articles including alloys, and processes of forming alloys. More specifically, the present invention is directed to a nickel-iron-base alloy and a process of forming a nickel-iron-base alloy.

BACKGROUND OF THE INVENTION

The operating temperature within a gas turbine engine 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 engine, atmospheric air is compressed to 10-25 times atmospheric pressure, and adiabatically heated 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, 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 engine, and the exhaust system, where the gases provides sufficient thrust to propel the aircraft. To improve the efficiency of operation of the engine, 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.

Demand for enhanced performance continues to increase. This demand for enhanced performance applies for newer engines and modifications of proven designs. Specifically, higher thrusts and better fuel economy are among the performance demands. To improve the performance of engines, the combustion temperatures have been raised to very high temperatures. This can result in higher thrusts and/or better fuel economy.

Stator components (nozzles and shrouds) are hot gas path components for gas turbines. It is desirable for the stator components to have oxidation resistance, thermal-mechanical fatigue capability and high temperature creep strength. Traditionally, the stator components are made of Ni-based or Co-based cast superalloys. These superalloys suffer from the drawback that they can have very high costs.

Known attempts to use different materials have been unsuccessful. For example, advanced stainless steels (for example Alumina-Forming Austenitic (AFA) alloys, developed by Oak Ridge National Laboratory) contain nano-precipitates and oxide-forming elements and demonstrate an outstanding heat-resistance. However, these advanced stainless steels have undesirably low creep strength for nozzles. Particularly, the creep strength of these advanced stainless steels only reaches about one half of design requirement for gas turbine nozzles.

Another group of low cost alternative materials, nickel-iron-base superalloys including A286, INCOLOY® 901, INCOLOY® 903 and IN706, have been regarded as suffering from several drawbacks. “INCOLOY” is a federally registered trademark of alloy produced by Inco Alloys International, Inc., Huntington, W. Va. For example, INCOLOY® 901 has been regarded as lacking gamma prime phases (resulting in low creep strength), containing significant amounts of eta, sigma, and laves phases (resulting in low ductility and/or poor long-term mechanical properties), and having a wide solidification range and poor castability.

A nickel-iron-base alloy and a process of forming a nickel-iron-base alloy that do not suffer from the above drawbacks is desirable in the art.

SUMMARY

According to an exemplary embodiment of the present disclosure, a nickel-iron-base alloy having by weight about 0.06% to about 0.09% C, about 35% to about 37% Fe, about 12.0% to about 16.5% Cr, about 1.0% to about 2.0% Al, about 1.0% to about 3.0% Ti, about 1.5% to about 3.0% W, up to about 5.0% Mo, up to about 0.75% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and balance essentially Ni.

According to another exemplary embodiment of the present disclosure, a nickel-iron-base alloy has a solidification range of less than about 110° F., a gamma prime solvus of greater than about 1700° F., substantially no eta phase, a laves phase of less than about 5%, a sigma phase of less than about 5%, and is devoid of Co.

According to another exemplary embodiment of the present disclosure, a process of forming a modified alloy includes providing a base alloy composition, identifying a plurality of predetermined properties, and modifying the base alloy composition to form a modified alloy composition having the plurality of predetermined properties. The plurality of predetermined properties includes having a solidification range of less than about 110° F., having a gamma prime solvus of greater than about 1700° F., having substantially no eta phase, having a laves phase of less than about 5%, and having a sigma phase of less than about 5%. The base alloy composition includes one or more of a first composition comprising about 0.05% C, about 36% Fe, about 12.50% Cr, about 0.20% Al, about 2.80% Ti, up to about 0.12% W, about 5.70% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, balance essentially Ni and a second composition including about 0.02% C, about 37% Fe, 16.00% Cr, about 0.20% Al, about 1.75% Ti, up to about 0.12% W, up to about 0.12% Mo, about 2.90% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, balance essentially Ni.

One advantage of an embodiment of the present disclosure includes the modified alloy having a desirable creep strength through the formation of sufficient amount of gamma prime phase and reduced or eliminated Eta phase.

Another advantage of an embodiment of the present disclosure includes the modified alloy having desirable ductility and/or long-term mechanical properties.

Another advantage of an embodiment of the present disclosure includes the modified alloy having desirable castability.

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.

DETAILED DESCRIPTION

Provided is a nickel-iron-base alloy having a plurality of predetermined properties and a process of forming a nickel-iron-base alloy having a plurality of predetermined properties.

Embodiments of the present disclosure involve a nickel-iron-base alloy formed from one or more low cost alloys previously regarded as unsuitable for hot gas path components such as engine turbine stators. The nickel-iron-base alloy does not contain Eta phaseresulting in a desirable creep strength. The nickel-iron-base alloy has desirable ductility and/or long-term mechanical properties. Also, the nickel-iron-base alloy has desirable castability.

The nickel-iron-base alloy can be formed by any suitable process. In one embodiment, the nickel-iron-base alloy has a creep rupture life of about 1000 hours at about 1400° F. and at about 25 ksi to about 30 ksi of loading. In one embodiment, the nickel-iron-base alloy is resistant to oxidation for 48,000 hours. In one embodiment, low cycle fatigue of the modified alloy is substantially the same as FSX414 alloy.

In one embodiment, the process includes providing a base alloy. The base alloy is one or more alloys previously considered undesirable for hot gas path components. For example, in one embodiment, the base alloy is Base Alloy 1. As used herein, “Base Alloy 1” refers to an alloy having a composition of about 0.05% C, about 0.20% Al, about 2.80% Ti, about 12.50% Cr, about 5.70 Mo, about 36% Fe, and other suitable elements (throughout the disclosure, all percents are by weight unless otherwise specified). In one embodiment, Base Alloy 1 further includes up to about 0.12% W, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si., up to about 0.006 B, and a balance essentially Ni. In a further embodiment, Base Alloy 1 does not include Co.

In another embodiment, the base alloy is Base Alloy 2. As used herein, “Base Alloy 2” refers to an alloy having a composition of about 16.00% Cr, about 37% Fe, about 2.90% Nb, about 1.75 Ti, about 0.20% Al, about 0.02% C, and other suitable elements. In one embodiment, Base Alloy 2 further includes up to about 0.12% W, up to about 0.2% Mn, up to about 0.1% Si., up to about 0.006 B, and a balance essentially Ni. In a further embodiment, Base Alloy 2 does not include Co.

The process continues by identifying a plurality of predetermined properties desired for the modified alloy. Data corresponding to the plurality of predetermined properties can be analyzed by a computer executed program such as a computational thermodynamic modeling program. The computer executed program correlates data regarding the base alloys and generates outputs of properties corresponding to the modified alloy. The outputs generated are based upon the modifications to composition of the base alloy that form the modified alloy. Analysis of the generated outputs permits identification of one or more compositions to be further analyzed.

The properties include any suitable quantifiable properties. The properties include a solidification range, a gamma prime solvus, a lack of eta phase, a laves phase percent, a sigma phase percent, a laves phase formation temperature, other suitable properties, or any combination thereof In one embodiment, the solidification range is less than about 110° F. resulting in good castability. In one embodiment, the gamma prime solvus is greater than about 1700° F. In one embodiment, the lack of eta phase includes being devoid of eta phase. In one embodiment, the laves sigma percent is less than about 5%. In one embodiment, the formation temperature is less than about 1200° F.

The correlation of data regarding the base alloys and outputs of properties corresponding to the nickel-iron-base alloy can involve any suitable relationship between compositional modifications to the base alloy and properties affected. For example, Al reduces eta phase. Including a concentration of greater than about 1% Al eliminates eta phase. Thus, the correlation of data can generate an output indicating an absence of eta phase upon a concentration of Al exceeding about 1%. Other relationships that can be correlated are that increasing the concentration of Mo increases eta phase, increasing the concentration of W reduces eta phase, increasing the concentration of Al reduces the solidification range, and combinations thereof. Combined correlations can also be utilized. For instance, when Al is at about 0.8%, increasing the concentration of W increases solidification. However, when Al is at about 1.5%, increasing the concentration of W reduces solidification. Thus, the concentration of Al and the concentration of W can be related in the correlation.

The correlation can further include additional experimental data based upon analysis of a component formed with the nickel-iron-base alloy and comparisons of the predetermined properties for different compositions of the nickel-iron-base alloy. For example, the data can include any combination of specific chemistries, scale-up heats, long-term microstructure stability studies, long-term oxidation tests, creep tests (for example 5,000 hour creep tests), and other mechanical property tests.

Based upon the correlation, a selection (either manual or automatic) of the base alloy(s) utilized and modified nickel-iron-base alloy(s) to be formed into the component is made. The component can be formed by any suitable technique (for example, casting, forging, heat treating, repair welding, or any suitable combination thereof).

In one embodiment, the nickel-iron-base alloy includes a compositional range of about 0.07% to about 0.09% C, about 35% to about 37% Fe, about 12.0% to about 16.5% Cr, about 1.0% to about 2.0% Al, about 2.0% to about 3.0% Ti, about 2.0% to about 3.0% W, about 3.0% to about 5.0% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy includes a compositional range of about 0.07% to about 0.09% C, about 35% to about 37% Fe, about 12.0% to about 13.0% Cr, about 1.35% to about 1.65% Al, about 2.25% to about 2.75% Ti, about 2.3% to about 2.7% W, about 3.4% to about 3.6% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy is devoid of Co.

In another embodiment, the nickel-iron-base alloy includes a compositional range of about 0.07% to about 0.09% C, about 35% to about 37% Fe, about 12.0% to about 16.5% Cr, about 1.0% to about 2.0% Al, about 2.0% to about 3.0% Ti, about 1.5% to about 2.5% W, about 3.0% to about 5.0% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy includes a compositional range of about 0.07% to about 0.09% C, about 35% to about 37% Fe, about 13.5% to about 14.5% Cr, about 1.35% to about 1.65% Al, about 2.25% to about 2.75 Ti, about 1.8% to about 2.2% W, about 3.9% to about 4.1% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy is devoid of Co.

In one embodiment, the nickel-iron-base alloy includes a compositional range of about 0.07% to about 0.09% C, about 35% to about 37% Fe, about 12.0% to about 16.5% Cr, about 1.0% to about 2.0% Al, about 2.0% to about 3.0% Ti, about 1.5% to about 2.5% W, about 0.5% to about 1.5% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy includes a compositional range of about 0.07% to about 0.09% C, about 35% to about 37% Fe, about 15.5% to about 16.5% Cr, about 1.35% to about 1.65% Al, about 2.25% to about 2.75 Ti, about 1.8% to about 2.2% W, about 0.9% to about 1.1% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy is devoid of Co.

In one embodiment, the nickel-iron-base alloy includes a compositional range of about 0.06% to about 0.08% C, about 35% to about 37% Fe, about 12.0% to about 16.5% Cr, about 1.0% to about 2.0% Al, about 1.0% to about 2.5% Ti, about 1.5% to about 2.5% W, up to about 0.25% Mo, about 0.25% to about 0.75% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy includes a compositional range of about 0.06% to about 0.08% C, about 35% to about 37% Fe, about 15.5% to about 16.5% Cr, about 1.35% to about 1.65% Al, about 1.5% to about 1.8% Ti, about 1.8% to about 2.2% W, up to about 0.12% Mo, about 0.4% to about 0.6% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In a further embodiment, the nickel-iron-base alloy is devoid of Co.

In one embodiment, the nickel-iron-base alloy can have a composition originally based upon the composition of Base Alloy 1. In one embodiment, the nickel-iron-base alloy includes a composition of about 0.08% C, about 36% Fe, about 12.5% Cr, about 1.50% Al, about 2.50% Ti, about 2.50% W, about 3.50% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In another embodiment, the nickel-iron-base alloy includes a composition of about 0.08% C, about 36% Fe, about 14.0% Cr, about 1.50% Al, about 2.50% Ti, about 2.50% W, about 4.00% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni. In another embodiment, the nickel-iron-base alloy includes a composition of about 0.08% C, about 36% Fe, about 16.0% Cr, about 1.50% Al, about 2.50% Ti, about 2.50% W, about 1.00% Mo, up to about 0.1% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni.

In one embodiment, the nickel-iron-base alloy can have a composition originally based upon the composition of Base Alloy 2. In one embodiment, the nickel-iron-base alloy includes a composition of about 0.07% C, about 37% Fe, about 16.0% Cr, about 1.50% Al, about 1.75% Ti, about 2.00% W, up to about 0.12% Mo, about 0.50% Nb, up to about 0.2% Mn, up to about 0.1% Si, up to about 0.006% B, and a balance essentially Ni.

In one embodiment, the composition of the alloy is used in hot gas turbine components. For example, the alloy can be used in stator components including, but not limited to, a nozzle, a shroud, other suitable portions, 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.