Nickel-Base Alloys

The present application claims priority to co-pending U.S. nonprovisional patent application Ser. No. 17/751,919, filed May 24, 2022, which in turn claims priority to U.S. provisional patent application Ser. No. 63/220,057, filed on Jul. 9, 2021, now expired. The entire disclosures of the foregoing applications are hereby incorporated herein by reference.

The present disclosure relates to nickel-base alloys.

Nickel-base alloys are used in aerospace, aeronautic, defense, marine, energy, and automotive applications including, for example, gas turbines, super critical carbon dioxide devices, concentrating solar plants, and ultra-super critical steam applications. These applications can be demanding on the nickel-base alloy and can require an advantageous combination of strength, weldability, formability, oxidation resistance, and microstructural stability at temperatures in excess of 1400° F. (760° C.). Developing a nickel base alloy that exhibits an advantageous combination of strength, creep resistance, weldability, formability, oxidation resistance, and microstructural stability at temperature above 1400° F. (760° C.) presents certain challenges.

One of the challenges encountered is that in order to achieve desired strength at these high temperatures through precipitation hardening, weldability and formability are reduced. This is evidenced, for example, by the known fabricability issues related to Rene 41 and Waspaloy alloys, both of which exhibit rapid age hardening and, as a result, can be difficult to form and weld. To address this fabricability issue, UNS N07208 reportedly was designed to simultaneously optimize strain age cracking, microstructural stability, and creep-rupture strength. While a favorable combination of properties has been reported for UNS N07208, this came at the expense of creep-rupture (compared to Rene 41 alloy) and strain age cracking (compared to Nimonic 263 alloy). Therefore, further improvement in creep-rupture, microstructural stability, and strain age cracking resistance is highly desirable.

A nickel-base alloy of the present disclosure comprises, in weight percentages based on the total weight of the nickel-base alloy: 1.6% to 3% aluminum; 0.3% to 1.5% titanium; 1.5% to 2.4% tantalum; nickel; and impurities.

Additional embodiments of a nickel-base alloy of the present disclosure comprise, in weight percentages based on the total weight of the nickel-base alloy: 1.6% to 3% aluminum; 0.3% to 1.5% titanium; 1.5% to 4% tantalum; 16% to 23% chromium; 5% to 20% cobalt; 4% to 10% molybdenum; 0 to 5% tungsten; nickel; and impurities. Certain non-limiting embodiments of the nickel-base alloy have a composition according to one or more of the following equations:

Additional embodiments of a nickel-base alloy of the present disclosure comprise, in weight percentages based on the total weight of the nickel-base alloy: 1.6% to 3% aluminum; 0.3% to 1.5% titanium; 1.5% to 4% tantalum; 16% to 23% chromium; 5% to 20% cobalt; 4% to 10% molybdenum; 0 to 5% tungsten; 0 to 1.2% niobium; 0 to 0.5% carbon; 0 to 0.1% boron; 0 to 5% iron; 0 to 2% manganese; 0 to 2% vanadium; 0 to 2% copper; 0 to 1% silicon; 0 to 1% zirconium; 0 to 1% hafnium; 0 to 1% rhenium; a total of 0 to 1% of rare earth elements; nickel; and impurities.

Additional embodiments of a nickel-base alloy of the present disclosure comprise, in weight percentages based on the total weight of the nickel-base alloy: 1.6% to 2.7% aluminum; 0.4% to 1.4% titanium; 1.6% to 3% tantalum; 17% to 21% chromium; 6% to 19% cobalt; 5% to 10% molybdenum; 0 to 3% tungsten; nickel; and impurities. Certain non-limiting embodiments of the nickel-base alloy have a composition according to one or more of the following equations:

Additional embodiments of a nickel-base alloy of the present disclosure comprise, in weight percentages based on total weight of the nickel-base alloy: 1.6% to 2.7% aluminum; 0.4% to 1.4% titanium; 1.6% to 3% tantalum; 17% to 21% chromium; 6% to 19% cobalt; 5% to 10% molybdenum; 0 to 3% tungsten; 0 to 0.9% niobium; 0 to 0.2% carbon; 0 to 0.05% boron; 0 to 3% iron; 0 to 2% manganese; 0 to 2% vanadium; 0 to 2% copper; 0 to 1% silicon; 0 to 1% zirconium; 0 to 1% hafnium; 0 to 1% rhenium; a total of 0 to 1% of rare earth elements; titanium; and impurities.

Additional embodiments of a nickel-base alloy of the present disclosure comprise, in weight percentages based on total weight of the nickel-base alloy: 1.7% to 2.4% aluminum; 0.5% to 1.3% titanium; 1.7% to 2.9% tantalum; 17% to 21% chromium; 7% to 18% cobalt; 6% to 9.5% molybdenum; 0 to 1% tungsten; nickel; and impurities. Certain non-limiting embodiments of the nickel-base alloy have a composition according to one or more of the following equations:

Additional embodiments of a nickel-base alloy of the present disclosure comprise, in weight percentages based on total weight of the nickel-base alloy: 1.7% to 2.4% aluminum; 0.5% to 1.3% titanium; 1.7% to 2.9% tantalum; 17% to 21% chromium; 7% to 18% cobalt; 6% to 9.5% molybdenum; 0 to 1% tungsten; 0 to 0.5% niobium; 0 to 0.2% carbon; 0 to 0.05% boron; 0 to 1.5% iron; 0 to 2% manganese; 0 to 2% vanadium; 0 to 2% copper; 0 to 1% silicon; 0 to 1% zirconium; 0 to 1% hafnium; 0 to 1% rhenium; a total of 0 to 1% of rare earth elements; titanium; and impurities.

The examples set out herein illustrate certain embodiments, in one form, and such examples are not to be construed as limiting the scope of the appended claims in any manner.

The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of various non-limiting and non-exhaustive embodiments according to the present disclosure.

Various non-limiting embodiments are described and illustrated in this specification to provide an overall understanding of the disclosed inventions. It is understood that the various non-limiting embodiments described and illustrated in this specification are non-limiting and non-exhaustive. Thus, the invention is not limited by the description of the various non-limiting and non-exhaustive embodiments disclosed in this specification. Rather, the invention sought to be patented is defined solely by the claims. The features and characteristics illustrated and/or described in connection with various non-limiting embodiments may be combined with the features and characteristics of other non-limiting embodiments. Such modifications and variations are intended to be included within the scope of this specification. As such, the claims may be amended or supplemented to recite any features or characteristics expressly or inherently described in, or otherwise expressly or inherently supported by, this specification. Further, applicant reserves the right to amend the claims to affirmatively disclaim features or characteristics that may be present in the prior art. The various non-limiting embodiments disclosed and described in this specification can comprise, consist of, or consist essentially of the features and characteristics as variously described herein.

All percentages and ratios provided herein for an alloy composition are based on the total weight of the particular alloy composition, unless otherwise indicated herein.

Any patent, publication, or other disclosure material that is said to be incorporated, in whole or in part, by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein is only incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

In this specification, other than where otherwise indicated, all numerical parameters are to be understood as being prefaced and modified in all instances by the term “about”, in which the numerical parameters possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described in the present description should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Also, any numerical range recited in this specification is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited in this specification is intended to include all lower numerical limitations subsumed therein, and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. All such sub-ranges are intended to be inherently described in this specification such that amending to expressly recite any such sub-ranges would comply with the requirements of 35 U.S.C. §§ 112 and 132(a). Additionally, as used herein when referring to compositional elemental ranges, the term “up to” includes zero unless the particular element is an unavoidable impurity.

The grammatical articles “one”, “a”, “an”, and “the”, as used in this specification, are intended to include “at least one” or “one or more”, unless otherwise indicated. Thus, the grammatical articles are used in this specification to refer to one or more than one (i.e., to “at least one”) of the grammatical objects of the article. By way of example only, “a component” means one or more components and, thus, possibly, more than one component is contemplated and may be employed or used in an implementation of the described embodiments. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.

Reference herein to a nickel-base alloy “comprising” a particular composition is intended to encompass alloys “consisting essentially of” or “consisting of” the stated composition. It will be understood that nickel-base alloy compositions described herein that “consist of” or “consist essentially of” a particular composition also may include impurities.

In the present disclosure, [Nb], [Ta], [Co], [W], [Al], [Ti], and [Mo] refer to weight percentage concentrations of, respectively, niobium, tantalum, cobalt, tungsten, aluminum, titanium, and molybdenum in an alloy, wherein the weight percentage concentrations are based on total weight of the alloy.

It can be challenging to formulate a nickel-base alloy that exhibits an advantageous combination of strength (e.g., creep, yield strength, and/or tensile strength), weldability, formability (e.g., hardness and/or elongation), oxidation resistance, and microstructural stability. For example, there may be tradeoffs between strength, weldability, formability, oxidation resistance, and microstructural stability in a nickel-base alloy formulation such that an improvement in one property is accompanied by a deterioration in another of the properties. For example, previously it has been observed that formulating a nickel-base alloy to improve creep resistance may be accompanied by a decrease in weldability and/or formability of the alloy.

As is understood in the art, “creep” refers to time-dependent strain occurring under continuous stress below the material's yield strength, such as, for example, at elevated temperature under a load. As used herein in connection with creep, “elevated temperature” refers to temperatures in excess of about 200° F. (93.3° C.). “Stress rupture” is the time at which a metallic article ruptures when subjected to a given sustained load at a given temperature. “Creep strength”, also known as “creep limit”, is a measure of a material's resistance to creep. It is also described as the stress under particular conditions that results in a particular creep rate. In other words, creep strength may be considered the combination of stress, temperature, and time required to reach a particular percentage of creep or rupture. The stress rupture for an alloy article is generally indicative of its creep strength. A higher stress rupture value indicates higher creep strength for an alloy article.

The stress rupture properties of metallic articles comprising nickel-base superalloys at elevated temperature can depend on many factors, including the composition of the matrix and microstructural features. The microstructure of nickel-base alloys can include various phases, such as, for example, a gamma (γ)-phase, which has a face-centered cubic lattice, and a gamma prime (γ′)-phase, which has a primitive cubic lattice. The γ-phase forms a matrix in which the γ′-phase precipitates.

Embodiments of the nickel-base alloy provided herein can comprise an advantageous combination of strength, weldability, formability, oxidation resistance, and microstructural stability. For example, embodiments of the nickel-base alloy provided herein can exhibit an enhanced stress rupture life while maintaining and/or enhancing the weldability and/or formability of the nickel-base alloy. Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure comprise, in weight percentages based on total weight of the nickel-base alloy: 1.6% to 3% aluminum; 0.3% to 1.5% titanium; 1.5% to 4% tantalum; nickel; and impurities. Additional embodiments of a nickel-base alloy according to the present disclosure comprise, in weight percentages based on total weight of the nickel-base alloy: 1.6% to 3% aluminum; 0.3% to 1.5% titanium; 1.5% to 4% tantalum; to 23% chromium; 5% to 20 nickel; 4% to 10% molybdenum; 0 to 5% tungsten; 0 to 1.2% niobium; nickel; and impurities.

The present inventors observed that the addition of tantalum and, if present, niobium in the alloy of the present disclosure can inhibit secondary carbide precipitation. The addition of tantalum and/or niobium in excess of a concentration that forms carbides (e.g., tantalum carbide, niobium carbide) can increase the stability of various carbides within the nickel-base alloy. For example, niobium and tantalum can form primary carbides (i.e., MC carbides) and inhibit precipitation of secondary carbides at grain boundaries and within the grains. The enhanced microstructural stability resulting from tantalum and, if present, niobium addition can lead to enhanced long-term elevated temperature properties such as, for example, increased stress rupture life.

The composition of the nickel-base alloy according to the present disclosure can comprise an amount of niobium and/or tantalum that satisfies the following equation, in weight percentage concentrations based on total weight of the nickel-base alloy:

For example, certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise niobium and/or tantalum in concentrations that satisfy the following equation, wherein the concentrations are weight percentage concentrations based on total weight of the nickel-base alloy:

In addition, certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise niobium and/or tantalum in concentrations that satisfy the following equation, wherein the concentrations are weight percentage concentrations based on total weight of the nickel-base alloy:

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 1.5% to 4% tantalum, such as, for example, 1.5% to 3.9%, 1.6% to 3.5%, 1.6% to 3%, 1.6% to 2.6%, 1.7% to 2.4%, 1.7% to 2.9%, 1.8% to 2.6%, 1.8% to 3%, 1.9% to 3%, 2% to 4%, or 2% to 3% tantalum.

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 0 to 1.2% niobium, such as, for example, 0.75% to 1.2%, 0.8% to 1.2%, 0.8% to 1.1%, 0.8% to 1.0%, 0.9% to 1.2%, 0.9% to 1.1%, 0.95% to 1.2%, 1% to 1.2%, 0 to 0.9%, or 0 to 0.5% niobium.

In embodiments of the nickel-base alloy according to the present disclosure, the aluminum and titanium concentrations are balanced in relation to the tantalum content and, if present, niobium content to control the content of γ′-phase in the nickel-base alloy so as to provide desired weldability, stability of the γ′-phase, and strength. The aluminum concentration in the alloy preferably is at least 1.6 weight percent, based on the total weight of the alloy. The concentration of titanium can be increased to increase alloy strength, but the titanium concentration in the alloy preferably is no greater than 1.5 weight percent, based on the total weight of the nickel-base alloy, so as to control the stability of the γ′-phase. Aluminum content also influences alloy strength, and its content relative to titanium, niobium, and tantalum contents influences the stability of the γ′-phase and can limit the phase fraction of gamma prime in the alloy. In certain embodiments of the alloy, the elemental additions are balanced so that the titanium concentration is decreased in relation to the concentrations of tantalum, aluminum, and, if present, niobium in order to provide desirable strength but also control γ′-phase content and provide desired weldability and stability of the γ′-phase.

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 1.6% to 3% aluminum, such as, for example, 1.6% to 2.7%, 1.6% to 2.5%, 1.7% to 2.4%, 1.7% to 2.7%, 1.8% to 3%, 1.9% to 3%, 2% to 3%, 2% to 2.7%, or 1.7% to 2.5% aluminum.

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 0.3% to 1.5% titanium, such as, for example, 0.4% to 1.4%, 0.6% to 1.3%, 0.4% to 1.4%, 0.5% to 1.5%, 0.3% to 1.3%, or 0.5% to 1.3% titanium.

Weldability of a nickel-base alloy according to the present disclosure may be influenced by the content of aluminum, titanium, tantalum and, if present, niobium in the alloy. In certain non-limiting embodiments, a nickel-base alloy according to the present disclosure having favorable weldability properties can comprises concentrations of aluminum, titanium, tantalum and, if present, niobium that satisfy the following equation, wherein the concentrations are weight percentage concentrations based on total weight of the nickel-base alloy:

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure having favorable weldability properties can comprises concentrations of aluminum, niobium, titanium, tantalum and, if present, niobium that satisfy the following equation, wherein the concentrations are weight percentage concentrations based on total weight of the nickel-base alloy:

Cobalt, chromium, and molybdenum can enhance the strength of the nickel-base alloy when in solid solution, but also promote formation of topologically closed-packed (TCP) phases (e.g., μ-phase, σ-phase) in the alloy after long holds at elevated temperatures. Inhibiting formation of TCP phases can increase the ductility of the nickel-base alloy. The alloy's cobalt concentration can affect the ductility and the stress rupture life of the nickel-base alloy. For example, increasing cobalt concentration can increase the creep strength of the nickel-base alloy. The chromium and molybdenum concentrations can reduce stability of the γ-phase, but they can improve stress rupture properties at elevated temperatures. Chromium can improve hot corrosion and oxidation resistance of the nickel-base alloy.

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 5% to 20% cobalt, such as, for example, 5% to 16%, 6% to 20%, 6% to 19%, 7% to 18%, 10% to 20%, 5% to 15%, or 10% to 15% cobalt.

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 16% to 23% chromium, such as, for example, 17% to 23%, 18% to 23%, 16% to 21%, 17% to 21%, 18% to 21%, or 18% to 20% chromium.

Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 4% to 10% molybdenum, such as, for example, 5% to 10%, 4% to 9%, 5% to 9%, 4% to 8%, 6% to 9.5%, or 5% to 8% molybdenum.

Tungsten can enhance stress rupture performance of the nickel-base alloy. Tungsten can build up at the γ-γ′-interface and can slow the coarsening rate of the γ′-phase precipitates due to the slow diffusion of tungsten from the γ-γ′-interface into the gamma matrix. Tungsten can also contribute to solute drag on dislocation motion through the γ-phase at elevated temperatures. In various non-limiting embodiments, the coefficient of thermal expansion (CTE) for the nickel-base alloy can decrease if tungsten and titanium concentrations are increased and the aluminum concentration is decreased. In various non-limiting embodiments, the concentrations of tungsten and cobalt in the nickel-base alloy can be balanced in order to limit formation of TCP phases. Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 0 to 5% tungsten, such as, for example, greater than 0 to 5%, greater than 0 to 4%, 0.1% to 5%, 1% to 5%, 1.5% to 3%, 1.5% to 2.5%, 3% to 5%, 2% to 3.5%, or 3.5% to 4.5% tungsten.

Carbon and boron concentrations can enhance stress rupture properties of the nickel-base alloy while maintaining desirable weldability. Certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 0 to 0.5% carbon, such as, for example, greater than 0 to 0.5%, greater than 0 to 0.4%, 0 to 0.2%, 0 to 0.1%, 0.01% to 0.5%, 0.01% to 0.2%, 0.01% to 0.1%, 0 to 0.2%, 0.02 to 0.5%, 0.02 to 0.3%, 0.02 to 0.1%, 0.03 to 0.5%, 0.03 to 0.3%, 0.03 to 0.1%, or 0.04% to 0.5% carbon. Also, certain non-limiting embodiments of a nickel-base alloy according to the present disclosure can comprise, in weight percentage concentrations based on total weight of the nickel-base alloy, 0 to 0.1% boron, such as, for example, greater than 0 to 0.1%, greater than 0 to 0.05%, 0 to 0.05%, 0 to 0.01%, 0.001% to 0.1%, 0.001% to 0.05%, or 0.001% to 0.01% boron.