阅读说明：本技术 具有优化性能和有限密度的超合金 (Superalloy with optimized performance and finite density ) 是由 P·J·萨勒特 C·德斯格兰杰斯 A-L·卢费 J-P·F·寇兹涅 G·迪拉斯 I·G·古 于 2020-03-13 设计创作，主要内容包括：本发明涉及新型超合金组合物,其具有有限密度,并且在高温时呈现出良好机械性能和良好的抗氧化性和耐腐蚀性。(The present invention relates to novel superalloy compositions having limited density and exhibiting good mechanical properties and good oxidation and corrosion resistance at high temperatures.)

1. A nickel-base superalloy comprising, in atomic percent, 13 to 21% chromium, 15 to 26% cobalt, 4 to 10% aluminum, 4.5 to 10% titanium, 8 to 18% iron, optionally 0.5 or less atomic percent boron, optionally 1 or less atomic percent carbon, optionally at least one additional element selected from molybdenum, tungsten, tantalum, and niobium, the total atomic content of the additional elements being less than or equal to 1.5%, the balance being nickel and unavoidable impurities, and the sum of the atomic percent of aluminum and titanium being 8.5 to 15%.

2. A cobalt-based superalloy comprising, in atomic percent, 9% to 20% chromium, 22% to 36% nickel, 4% to 10% aluminum, 4% to 10% titanium, 8% to 15% iron, optionally 0.5% or less by atomic percent boron, optionally 1% or less by atomic percent carbon, optionally at least one additional element selected from molybdenum, tungsten, tantalum, and niobium, the total atomic content of the additional elements being less than or equal to 1.5%, the balance being cobalt and unavoidable impurities, and the sum of the atomic percentages of aluminum and titanium being 8% to 15%.

3. The superalloy of claim 1 or 2, comprising 4.5 to 7.5 atomic percent aluminum.

4. The superalloy as in claim 1 or claim 3 when dependent on claim 1, wherein the superalloy comprises 15 atomic% to 22 atomic% cobalt.

5. The superalloy of claim 1, or any of claims 3 or 4 when dependent on claim 1, wherein the superalloy comprises 13 atomic% to 18 atomic% iron.

6. The superalloy of claim 1, comprising, in atomic percent, 13% to 21% chromium, 15% to 26% cobalt, 4% to 8% aluminum, 4.5% to 8% titanium, and 8% to 18% iron.

7. The superalloy of claim 6, comprising, in atomic percent, 13% to 17% chromium, 16% to 23% cobalt, 4% to 8% aluminum, 4.5% to 8% titanium, and 15% to 18% iron.

8. The superalloy of claim 7, comprising, in atomic percent, 16% to 17% chromium, 16% to 17% cobalt, 4.5% to 5.5% aluminum, 4.5% to 5.5% titanium, and 16% to 17% iron.

9. The superalloy of claim 7, comprising, in atomic percent, 13% to 14% chromium, 21.5% to 22.5% cobalt, 4.5% to 5.5% aluminum, 7% to 8% titanium, and 17% to 18% iron.

10. The superalloy of claim 6, comprising, in atomic percent, 13% to 21% chromium, 24% to 26% cobalt, 4% to 8% aluminum, 4.5% to 8% titanium, and 8% to 11% iron.

11. The superalloy of claim 10, comprising, in atomic percent, 19.5% to 20.5% chromium, 24.5% to 25.5% cobalt, 4.5% to 5.5% aluminum, 4.5% to 5.5% titanium, and 9.5% to 10.5% iron.

12. The superalloy of claim 10, comprising, in atomic percent, 13% to 14% chromium, 24.5% to 25.5% cobalt, 5% to 6% aluminum, 6.5% to 7.5% titanium, and 8.5% to 9.5% iron.

13. The superalloy as in claim 2 or claim 3 when dependent on claim 2, wherein the superalloy comprises 25 atomic% to 36 atomic% nickel.

14. A gas turbine engine part comprising the superalloy of any of claims 1-13.

15. A turbomachine comprising the gas turbine engine part of claim 14.

Technical Field

The present invention relates to novel superalloy compositions having limited density and exhibiting good mechanical properties and good oxidation and corrosion resistance at high temperatures. More particularly, the invention relates to the use of the superalloy to form an aircraft gas turbine engine part.

Prior Art

In the context of developing a new generation of aircraft turbines, materials with improved oxidation and corrosion resistance at high temperatures (typically in the range of 800 ℃ to 1000 ℃) and limited density are sought.

Therefore, High Entropy Alloys (HEA) or Complex Condensed Alloys (CCA) have been developed. In particular, studies have been conducted to identify new alloys having gamma prime hardening phase precipitates in the alloy matrix.

However, it has been observed that the microstructure of these alloys may be affected when exposed to high temperatures, as undesirable phase particles, i.e., topologically close-packed (TCP) phases, may occur. The presence of these phases can lead to a reduction in the mechanical properties of the alloy.

JP 2018-145456 is known to disclose high entropy alloys.

Therefore, there is a need to have a new alloy composition that has a limited density and exhibits good mechanical properties and good oxidation and corrosion resistance at high temperatures.

Disclosure of Invention

To this end, according to a first embodiment, the invention proposes a nickel-based superalloy comprising, in atomic percentage, 13% to 21% of chromium, 4% to 30% of cobalt, 4% to 10% of aluminum, 4.5% to 10% of titanium, 8% to 18% of iron, optionally less than or equal to 0.5% of boron, optionally less than or equal to 1% of carbon, optionally at least one additional element selected from molybdenum, tungsten, tantalum and niobium, the total atomic content of said additional elements being less than or equal to 1.5%, the remainder being nickel and unavoidable impurities, and the sum of the atomic percentages of aluminum and titanium being 8.5% to 15%.

According to a second embodiment, the invention also proposes a cobalt-based superalloy comprising, in atomic percentage, 9% to 20% of chromium, 22% to 36% of nickel, 4% to 10% of aluminum, 4% to 10% of titanium, 8% to 18% of iron, optionally less than or equal to 0.5% of boron, optionally less than or equal to 1% of carbon, optionally at least one additional element selected from molybdenum, tungsten, tantalum and niobium, the total atomic content of said additional elements being less than or equal to 1.5%, the remainder being cobalt and unavoidable impurities, and the sum of the atomic percentages of aluminum and titanium being 8% to 15%.

"X-based superalloy" refers to a superalloy having a majority of the atomic percent of the element X. Thus, element X is the element with the highest atomic percentage in the superalloy. The atomic percent of element X in the X-based superalloy can be (but is not required to be) greater than 50%.

"unavoidable impurities" are elements that are not intentionally added to the composition and brought along with other elements.

Both of the above embodiments relate to high entropy superalloys with a complex composition of a matrix called the gamma phase, where gamma' (L1)₂) The precipitates of the hardening phase are present in a significant volume fraction to optimize the mechanical properties at high temperatures. L1₂Volume fraction of precipitate (expressed as "x (L1)₂) ") preferably satisfies the following condition:

-50%. gtoreq.x (L1) at 800 ℃%₂) Not less than 40 percent; and is

-30%. gtoreq.x (L1) at 1000 ℃ ≥ 30 ≥ L₂)≥20％。

Furthermore, the superalloys according to both of the above embodiments advantageously have a lower tendency to form topologically close-packed phases. In these superalloys, the incorporation of an element selected from the group consisting of molybdenum, tungsten, tantalum and niobium is minimized (the sum of the four element contents being less than or equal to 1.5 atomic percent) in order to reduce its density. However, it should be noted that the controlled presence of the latter element may be advantageous to have the substrate and L1 in combination₂The phases are further hardened. The superalloy also has good oxidation and corrosion resistance at high temperatures.

The advantageous properties of the above-described superalloys will be repeated in the following description to illustrate the contribution of the various alloying elements.

Chromium provides the superalloy with good oxidation and corrosion resistance at high temperatures, typically in the temperature range of 800 ℃ to 1000 ℃. If the chromium content is too high, the solvus temperature of the gamma' phase will be lowered, i.e., above that temperature, these phases will dissolve in the gamma matrix. Above the solvus temperature, the gamma prime phase dissolves and no longer contributes to the superalloy hardness increase. Thus, chromium must be present in sufficient amounts to provide the desired oxidation and corrosion resistance, but its content must also be limited to keep the γ' phase precipitated over a wide temperature range to increase superalloy hardness. Limiting the chromium content in the superalloy also facilitates reducing the formation of topologically close-packed phases, in which iron is present as the sigma (sigma) phase or the B2 phase.

In the case of the first embodiment relating to nickel-based superalloys, cobalt allows for strengthening of the gamma-matrix and reduces the susceptibility to precipitation of topologically close-packed phases. Cobalt also slows down the diffusion of species, thus promoting the stability of the gamma prime precipitate. However, as for chromium, the cobalt content must be limited to keep the solvus temperature of the γ' phase high.

In a second embodiment of the cobalt-based superalloy, nickel extends the range of gamma-prime phase (gamma-prime phase) presence and the phase line. However, the nickel content must be limited to maintain the cobalt-doped gamma' phase and not form tau-Ti (Ni, Co) at the use temperature₃And (4) phase(s).

The aluminum and the titanium promote the composition to be between (Ni, Co)₃(Al, Ti) and Co₃Precipitation of gamma prime hardening phases between Ti. However, aluminum and titanium must be added in limited proportions so that the gamma-matrix always makes up a large part of the superalloy, thereby avoiding negative effects on mechanical properties at low temperatures.

Iron decreases the superalloy density because the density of this element is lower than nickel or cobalt. This is particularly advantageous when the superalloy is used in the aeronautical field, where it is of interest to be able to reduce the part mass. However, the proportion of iron must be limited so as not to promote the formation of iron oxides to damage chromium oxides and thereby maintain the desired oxidation and corrosion resistance at high temperatures.

If boride or carbide formation is sought in order to enhance grain boundary strength, other elements (i.e., boron or carbon) may be present in the superalloy as an option in limited amounts. Unavoidable impurities may then be present in an atomic percentage of less than or equal to 1000 ppm.

The next section describes preferred features of the superalloy composition.

In the case of the second embodiment, the superalloy may contain, in atomic percent, 13% to 21% chromium.

This high chromium content also improves oxidation and corrosion resistance at high temperatures.

In an exemplary embodiment, the superalloy comprises, in atomic percent, 4% to 8%, such as 4.5% to 8%, aluminum. The superalloy may include 4.5 to 7.5, such as 4.5 to 5.5, atomic percent aluminum.

This high aluminum content helps to optimize the overall mechanical properties of the alloy at high temperatures.

In an exemplary embodiment, the superalloy comprises, in atomic percent, 4.5% to 8% titanium.

This titanium content helps to optimize the overall mechanical properties of the alloy at high temperatures.

In an exemplary embodiment, the sum of the atomic percentages of aluminum and titanium is 9% to 13%.

This content helps to optimize the overall mechanical properties of the alloy at high temperatures.

In the case of the first embodiment, the superalloy may contain 15 to 26 atomic percent cobalt. In particular, the superalloy may include 15 to 22 atomic percent cobalt.

This cobalt content optimizes the trade-off between gamma matrix strengthening and gamma prime hardening phase stability provided by cobalt.

In the case of the first embodiment, the superalloy may contain 9 to 18 atomic percent iron. In particular, the superalloy may comprise 13 to 18 atomic percent iron, for example 14 to 18 atomic percent iron, or even 15 to 18 atomic percent iron.

This iron content optimizes the trade-off between superalloy degradation and oxidation and corrosion resistance at high temperatures.

In the case of the first embodiment, the sum of the atomic percentages of chromium and iron may be less than or equal to 35%, for example from 20% to 34%.

In the case of the first embodiment, the difference (Ni — Co) between the nickel atomic percent and the cobalt atomic percent may be 5% to 50%, for example, 10% to 48%.

In the case of the first embodiment, the superalloy may comprise, in atomic percent, 13% to 21% chromium, 4% to 30% cobalt, 4% to 8% aluminum, 4.5% to 8% titanium, and 8% to 18% iron.

In the case of the first embodiment, the superalloy may comprise, in atomic percent, 13% to 17% chromium, 16% to 23% cobalt, 4% to 8% aluminum, 4.5% to 8% titanium, and 15% to 18% iron.

In the case of the first embodiment, the superalloy may comprise, in atomic percent, 16% to 17% chromium, 16% to 17% cobalt, 4.5% to 5.5% aluminum, 4.5% to 5.5% titanium, and 16% to 17% iron.

In the case of the first embodiment, the superalloy may comprise, in atomic percent, 13% to 14% chromium, 21.5% to 22.5% cobalt, 4.5% to 5.5% aluminum, 7% to 8% titanium, and 17% to 18% iron.

In the case of the first embodiment, the superalloy may comprise, in atomic percent, 13% to 21% chromium, 24% to 26% cobalt, 4% to 8% aluminum, 4.5% to 8% titanium, and 8% to 11% iron.

In the case of the first embodiment, the superalloy may include, in atomic percent, 19.5% to 20.5% chromium, 24.5% to 25.5% cobalt, 4.5% to 5.5% aluminum, 4.5% to 5.5% titanium, and 9.5% to 10.5% iron.

In the case of the first embodiment, the superalloy may comprise, in atomic percent, 13% to 14% chromium, 24.5% to 25.5% cobalt, 5% to 6% aluminum, 6.5% to 7.5% titanium, and 8.5% to 9.5% iron.

In the case of the second embodiment, the superalloy may contain 25 to 36 atomic percent nickel.

In the case of the second embodiment, the superalloy may contain 8 to 15 atomic percent iron.

This iron content optimizes the trade-off between superalloy degradation and oxidation and corrosion resistance at high temperatures.

In the case of the second embodiment, the sum of the atomic percentages of chromium and iron may be between 18% and 35%, for example between 19% and 24%.

In the case of the second embodiment, the difference (Co — Ni) between the atomic percent of cobalt and the atomic percent of nickel may be less than or equal to 10%.

The invention also relates to a gas turbine engine part comprising the above superalloy. The gas turbine engine part may be an aircraft gas turbine engine part. The gas turbine engine part may be selected from: gas turbine engine disks, gas turbine engine casings, blades (blades), vanes (vanes), portions of combustors, portions of afterburners, turbine ring sector regions, thrust reversers or attachment elements (e.g., bolts).

The invention also relates to a gas turbine engine comprising the above gas turbine engine part. The gas turbine engine may be an aircraft gas turbine engine.

The structure and possible applications of the superalloy according to the present invention have just been described. The following sections describe details of the manufacture of superalloys in accordance with the present invention.

First, superalloys of the above composition may be obtained by conventional processes, such as Vacuum Arc Remelting (VAR) or Vacuum Induction Melting (VIM). Superalloy components may also be obtained by forging, extrusion or rolling. The part may also be obtained from powder formed by spraying a superalloy ingot.

Second, the solidified or formed blank is heat treated.

The microstructure may be heat treated to dissolve the gamma prime precipitates to eliminate segregation or to significantly reduce segregation if not eliminated. The treatment is carried out at a temperature above the solvus temperature of the gamma-prime phase and below the initial melting temperature of the superalloy (Tsolidus). The treatment may be carried out at a temperature greater than or equal to 1100 ℃, for example at a temperature of between 1100 ℃ and 1200 ℃.

Quenching may then be performed after the heat treatment to obtain a fine and uniform dispersion of the gamma' phase precipitates. During the quenching process, the superalloy may be cooled to a quench end temperature of less than or equal to 850 ℃, for example comprised between 20 ℃ and 850 ℃.

A tempering heat treatment may then be performed after quenching at a temperature below the solvus temperature of the gamma-prime phase to define the microstructure of the superalloy. The tempering heat treatment may be performed at a temperature of 750 ℃ to 1000 ℃. A stable microstructure is thereby obtained in which the gamma prime precipitates are present in significant amounts.

The resulting part may then be machined to adjust its dimensions.

Brief description of the drawings

FIG. 1 is a set of photographs showing the microstructure of various examples of the superalloy of the present invention.

FIG. 2 is a quantitative test of the volume fraction of thermal gamma prime precipitates in various examples of superalloys of the present invention.

FIG. 3 is a quantitative test result of the average radius of thermal gamma prime precipitates in various examples of superalloys of the present invention.

FIG. 4 is a quantitative test result showing experimental densities for various examples of the superalloy of the present invention.

FIG. 5 is the result of Differential Scanning Calorimetry (DSC) analysis performed on various examples of the superalloy of the present invention.

FIG. 6 is a test result comparing the compressibility of various examples of superalloys of the present invention with the compressibility of commercially available superalloys outside the scope of the present invention.

FIG. 7 shows the hardness change of an example of a superalloy of the present invention during annealing at 900 ℃.

Description of the embodiments

The inventors evaluated the performance of various examples of the superalloy of the present invention. The various tests that have been performed will be described in detail below.

The compositions evaluated are detailed in table 1. The contents of the different elements are expressed in atomic percent.

[ Table 1]

	Ni	Co	Cr	Fe	Al	Ti
							TA1	40.0	16.7	16.7	16.7	5.0	5.0
TA2	35.0	35.0	10.0	10.0	5.0	5.0
							TA3	35.0	25.0	20.0	10.0	5.0	5.0
TA4	52.5	4.4	13.1	17.5	7.5	5.0
							TA5	35.0	21.9	13.1	17.5	5.0	7.5

Alloys TA 1-TA 5 were heat treated in which the first step was carried out at 1150 ℃ for 48 hours and then the second step was carried out at 900 ℃ for 403 hours. FIG. 1 shows the microstructure of the alloys evaluated TA 1-TA 5. The photograph in fig. 1 shows the presence of gamma prime precipitates for each of alloys TA 1-TA 5.

Alloy TA 1-TA 5 was heat treated at 900 ℃ for 403 hours. The volume fraction of the γ' phase precipitate was evaluated using the following method: automatic thresholding was performed by taking 20 images at 5000 x magnification taken by a scanning electron microscope. Figure 2 quantifies the volume fraction of gamma prime precipitates of alloys TA 1-TA 5. It can be seen that the gamma prime precipitates occupy a significant volume fraction, providing the desired thermal hardening.

The average radius of the precipitate was also evaluated by the following method: the SEM image was thresholded to obtain about 1500 precipitates per composition (precipitates per composition), with an average of halfThe radius is defined as the radius of the equivalent area disc. The results are shown in fig. 3. It can be seen that a relatively small and relatively stable gamma' precipitate is obtained. Regardless of the embodiment considered, the average radius of the γ' precipitates may be less than or equal to 200 nm. It should be noted that the precipitate size remains stable even after exposure to high temperatures. Furthermore, it has been confirmed by measuring the oxidation kinetic constants that the superalloy of the present invention is obtained by forming chromium oxide Cr₂O₃The protective layer is protected and classified as a chromium former (former).

The experimental densities of alloys TA 1-TA 5 were quantified and the results are provided in FIG. 4. It can be seen that the superalloy of the present invention has a finite density, all densities being less than 8.1g/cm³。

The solution windows for alloys TA 1-TA 5 were evaluated by differential scanning calorimetry analysis (see FIG. 5). It can be seen that the solvus temperature of each alloy is relatively high and close to 1100 ℃, showing the effective contribution of these precipitates to the increase in hot hardness over a wide temperature range.

The compressibility of the alloys was evaluated in a Gleeble tester at 900 c and compared to the compressibility of a commercially available Inconel 718 alloy outside the scope of the invention (see fig. 6). The superalloy of the present invention has good mechanical properties, superior to Inconel 718 alloy, and a significantly lower density.

In contrast, FIG. 7 shows the change in hardness of alloy TA5 measured at 25 ℃ during the 900 ℃ anneal. The hardness of the alloy remains higher than 430H even after several hours at high temperature_V。

In addition to the alloy compositions shown in table 1 above, other examples of alloy compositions are also determined by the inventors to be preferred, i.e. (compositions given in atomic percent):

TA6 40.4% Ni-25.2% Co-13.1% Cr-8.8% Fe-5.5% Al-7% Ti; and

-TA7:28％Ni–37.6％Co–13.1％Cr–8.8％Fe–4.5％Al–8％Ti。

the terms "… to …" should be understood to include a limitation.