Nickel-based superalloy

Abstract

The present invention relates to a nickel-base superalloy having a composition advantageously and essentially consisting, in percentages by weight of the total composition, of Cr 10.0-11.25, Co 11.2-13.7, Mo 3.1-3.8, W 3.1-3.8, Al 2.9-3.5, Ti 4.6-5.6, Nb 1.9-2.3, Hf 0.25-0.35, Zr 0.040-0.060, C 0.010-0.030, B 0.01-0.03, the balance being Ni and unavoidable impurities, and no tantalum. The invention also relates to a powder of the superalloy according to the invention, a method for producing a component made of the superalloy according to the invention, and a component obtainable by this method.

Description

[Technical Field]

[0001] The present invention relates to the field of nickel-based superalloys for high temperature applications, developed for turbine disk applications with a dual coarse / fine grain structure, intended to withstand temperatures of the order of 800°C and temperature peaks up to 850°C in the hottest component parts, while retaining high mechanical strength in the cooler operating parts of the disk. [Background technology]

[0002] Due to new environmental standards (ACARE2020) and the demands of aircraft manufacturers to reduce overall costs, engine manufacturers are demanding improved performance from new generation turbojet engines, particularly with significantly reduced specific consumption. This requires increasing engine efficiency while simultaneously reducing the amount of ventilation in hot areas, especially the disks. This calls for materials with improved thermal properties. Summary of the Invention

[0003] Numerous advances have been made in materials to improve their temperature capabilities: more refractory materials, powder metallurgy techniques, etc. However, today the temperature improvements are very limited and the chemical composition of the material alone cannot meet the set objectives. In fact, the performance of materials for modern turbine disks depends on the ability to find the best compromise between the trade-offs between the various mechanical properties required for an optimized homogeneous microstructure.

[0004] One way to push the limits of current materials is to introduce microstructures into components, structures whose mechanical properties respond to the local stresses in the component, in other words, to introduce a dual or gradient microstructure into a given component. For example, a turbine disk, one of the most thermomechanically stressed components in a turbojet engine, requires both a fine-grained structure at the inner diameter of the disk for tensile and fatigue properties at intermediate temperatures, and a coarse-grained structure at the rim of the disk for creep and crack properties at high temperatures.

[0005] A heat treatment method for obtaining such a dual structure alloy is described in French Patent Application No. 3043410. This application presents a method for forming a gradient structure in a disc-shaped part through a heat treatment that itself has a temperature gradient, including an induction heat treatment, which makes it possible to solution heat treat the part at stepped temperatures.

[0006] In the highest temperature region, the temperature is above the melting point of the phase that occupies the grain boundaries, also called the solvus temperature (in the case of gamma-gamma prime nickel-based alloys, the phase in question is the gamma prime phase).

[0007] In the lowest high temperature region, the temperature is below this solvus temperature.

[0008] Thus, in regions where the temperature exceeds the solvus temperature of the gamma prime phase, the grains become larger to form a structure that is favorable for creep and crack properties, while in zones where the temperature remains below the solvus temperature, the structure retains the forged grain size, typically a relatively fine grain size that is favorable for tensile and fatigue properties.

[0009] Typically, gradient processing is applied to an existing "conventional" alloy to optimize its chemical composition, ensuring a homogeneous structure throughout the component and the best balance of required mechanical properties. Thus, the highest-performing superalloy for disk applications may exhibit a target operating temperature of 760°C, with an optional peak temperature of up to 800°C. However, the existing chemistry is not optimized for the gradient processing configuration. Therefore, to improve the component's performance, it is necessary to define a specific chemistry for the gradient processing of the component.

[0010] An example of a known nickel-based alloy is described in European Patent No. 1840232 or in the paper by JY. Gue'dou et al. ("Development of a Novel Fatigue- and Creep-Resistant PM Nickel-Based Superalloy for Disk Applications," Proceedings of Superalloys 2008). This alloy is sold under the standard N19 (SMO43).

[0011] This example alloy, like the alloys of the present invention, is one of the dual-phase alloys containing a so-called gamma phase, formed by a nickel-based solid solution forming the matrix of the metallurgical grains, and a so-called gamma-prime phase, whose structure is based on the oriented intermetallic compound Ni3Al. The gamma-prime phase forms multiple populations of intergranular and intragranular precipitates, which appear at different stages in the thermomechanical history of the alloy and have different roles in the alloy's mechanical behavior. Nickel-based superalloys are thus materials that have an atomic lattice cell very similar to that of a gamma-austenitic nickel-based matrix (face-centered cubic, and therefore relatively ductile) strengthened by gamma-prime hardening precipitates (structure L12) tightly bonded to the matrix.

[0012] The density of these alloys is also a concern, however, the prior art over the past decade has been directed towards using higher tantalum contents, which leads to increased alloy density.

[0013] Therefore, in addition to improved performance in terms of mechanical properties at the temperatures of the disk region under consideration, the chemical composition provides the alloy with the following unique properties: -Controlled density: <8500kg / m 3 ; Metallurgical stability up to -800 to 850°C (absence of TCP phases (Topological Compact Phases)); -Excellent oxidation resistance; The difference between the gamma prime solvus temperature and the combustion temperature of the alloy is large enough for the performance of the supersolvus treatment.

[0014] The inventors have surprisingly discovered that such properties can be obtained using a nickel-based superalloy that is tantalum-free and has a lower chromium content than the alloys described in EP 1840232, and in particular than the best performing commercial alloy (N19 / SMO43). [Brief explanation of the drawings]

[0015] [Figure 1] Figure 1 compares the elastic limit (in MPa as a function of temperature (°C) according to standard NF EN 2002-001 / 06) of the superalloy according to Example 1 with other disk alloys made by prior art powder metallurgical methods. [Figure 2] FIG. 2 compares the mechanical strength (in MPa as a function of temperature (° C.) according to standard NF EN 2002-001 / 06) of the superalloy according to Example 1 with other disk alloys produced by prior art powder metallurgical methods. DETAILED DESCRIPTION OF THE INVENTION

[0016] Accordingly, the present invention relates to a nickel-base superalloy having a composition, in percent by weight of the total composition, of: Chromium: 10.0-11.25, advantageously 10.0-11.0; Cobalt: 11.2-13.7, advantageously 12.0-13.0; Molybdenum: 3.1-3.8, advantageously 3.3-3.7; Tungsten: 3.1-3.8, advantageously 3.1-3.5; Aluminum: 2.9-3.5, advantageously 3.2-3.5; Titanium: 4.6-5.6, advantageously 4.6-5.0; Niobium: 1.9-2.3, advantageously 1.9-2.0; Hafnium: 0.25-0.35, advantageously 0.25-3.0; Zirconium: 0.040-0.060, advantageously 0.050-0.060; Carbon: 0.010-0.030, advantageously 0.015-0.025; Boron: 0.01-0.030, advantageously 0.01-0.02; Nickel: balance; and unavoidable impurities; and preferably consisting essentially of, and especially consisting of, a tantalum-free composition comprising:

[0017] Thus, the composition of the nickel-based superalloy according to the present invention comprises the following elements: -Main additive elements: Co, Cr, Mo, W, Al, Ti, Nb. - Minor additive elements (lower concentrations in mass percent): Hf, C, B, Zr.

[0018] Thus, the composition according to the invention contains chromium (Cr), in weight percent relative to the total weight of the composition, in the range of 10.0 to 11.25, advantageously 10.0 to 11.2, particularly 10.0 to 11.0, and more particularly 10.3 to 10.9, The chromium content is measured with an uncertainty of ±0.2, advantageously with an uncertainty of ±0.15.

[0019] The composition according to the invention further contains cobalt (Co) in a weight percent range of 11.2 to 13.7, preferably 12.0 to 13.0, in particular 12.2 to 12.8, based on the total weight of the composition, the Cobalt content being measured with an uncertainty of ±0.3, in particular ±0.2, preferably ±0.15.

[0020] The composition according to the invention further contains molybdenum (Mo) in the range of 3.1 to 3.8, preferably 3.2 to 3.7, and especially 3.3 to 3.7 weight percent relative to the total weight of the composition, the molybdenum content being measured with an uncertainty of ±0.04, especially ±0.02, and preferably ±0.01.

[0021] The composition according to the invention further contains tungsten (W) in a weight percent range of 3.1 to 3.8, preferably 3.1 to 3.5, and especially 3.1 to 3.3, based on the total weight of the composition, the tungsten content being measured with an uncertainty of ±0.04, especially ±0.02, and preferably ±0.01.

[0022] The composition according to the invention also contains aluminum (Al) in a weight percent range relative to the total weight of the composition of 2.9 to 3.5, preferably 3.2 to 3.5, in particular 3.2 to 3.4, the aluminum content being measured with an uncertainty of ±0.04, in particular ±0.02, preferably ±0.01.

[0023] The composition according to the invention further contains titanium (Ti) in a weight percent range of 4.6 to 5.6, advantageously 4.6 to 5.0, in particular 4.7 to 4.9, based on the total weight of the composition, the titanium content being measured with an uncertainty of ±0.2, in particular ±0.1.

[0024] The composition according to the invention further contains niobium (Nb) in a weight percent range of 1.9 to 2.3, preferably 1.9 to 2.0, based on the total weight of the composition, the niobium content being measured with an uncertainty of ±0.04, in particular ±0.02.

[0025] The composition according to the invention further contains hafnium (Hf) in a weight percent range of 0.25 to 0.35, advantageously 0.25 to 0.30, in particular 0.26 to 0.28, relative to the total weight of the composition, the hafnium content being measured with an uncertainty of about 10%.

[0026] The composition according to the invention additionally contains zirconium (Zr) in a weight percent range of 0.040 to 0.060, advantageously 0.050 to 0.060, particularly 0.055 to 0.060, and more particularly 0.056 to 0.058, based on the total weight of the composition, the zirconium content being measured with an uncertainty of about 10%.

[0027] The composition according to the invention also contains carbon (C) in a weight percentage range of 0.010 to 0.030, advantageously 0.015 to 0.025, in particular 0.019 to 0.023, relative to the total weight of the composition, the carbon content being measured with an uncertainty of ±0.003, in particular ±0.002.

[0028] The composition according to the invention also contains boron (B) in a weight percentage range of 0.01 to 0.03, especially 0.01 to 0.02, based on the total weight of the composition, the boron content being measured with an uncertainty of about 10%.

[0029] The elements W, Cr, Co, and Mo are primarily responsible for hardening the so-called gamma-austenitic matrix. In particular, the addition of the refractory elements Mo and W strengthens the gamma matrix through solid solution, improving the high-temperature resistance of the superalloy. However, their contents must remain limited to avoid the formation of weakening TCP phases and to avoid increasing the density of the alloy due to their large atomic weight.

[0030] Furthermore, the addition of Cr and Co reduces the gamma prime solvus temperature of the superalloy. Co is a chemically close element to Ni and partially replaces this element to form a solid solution in the gamma phase.

[0031] In an advantageous embodiment, the sum of the contents of W, Mo, Cr and Co is 25.5 to 29.5 in atomic %, ie 25.5≦W+Mo+Cr+Co≦29.5.

[0032] In another advantageous embodiment, the sum of the contents of W and Mo is 2.3 or more and 3.9 or less in atomic percentage, that is, 2.3 ≤ W + Mo ≤ 3.9.

[0033] Elements of Al, Ti, and Nb are advantageous for the precipitation of a hardening phase (Ni, Co)3(Al, Ti, Nb) called gamma prime phase.

[0034] Furthermore, by adding Cr and Al, the resistance of the superalloy to high-temperature oxidation and corrosion is improved.

[0035] Elements of Ti and Nb replace Al in the gamma prime phase and strengthen this phase. However, for advantage, in order to stabilize the eta or delta phase (Ni3Ti, Ni3Nb type) instead of the gamma prime phase and not destabilize the gamma prime phase, the ratio of the contents (Ti + Nb) / Al must be maintained less than​​​​​​​​​​​​​​​​​​​The unavoidable impurities in the compositions of the present invention are those that result from the superalloy manufacturing process or from impurities present in the raw materials used to manufacture the superalloy. These include all conventional impurities found in nickel-based superalloys, particularly those selected from the group consisting of manganese, silicon, vanadium, sulfur, phosphorus, copper, lead, iron, bismuth, nitrogen, oxygen, hydrogen, and mixtures thereof. These may constitute up to 1% by mass of the alloy, each representing up to 0.5% by weight of the total composition. Typically, the content of impurities in the alloy is measured with an uncertainty of 10%.

[0041] In an advantageous embodiment, the nickel-base superalloy of the present invention has a composition, in weight percent of the total composition, of: Chromium: 10.0-11.0, advantageously 10.3-10.9; Cobalt: 12.0-13.0, advantageously 12.2-12.8; Molybdenum: 3.2-3.7, advantageously 3.3-3.7; Tungsten: 3.1-3.5, advantageously 3.1-3.3; Aluminum: 3.2-3.5, advantageously 3.2-3.4; Titanium: 4.6-5.0, advantageously 4.7-4.9; Niobium: 1.9-2.0; Hafnium: 0.25-0.030, advantageously 0.26-0.028; Zirconium: 0.050-0.060, advantageously 0.055-0.060; Carbon: 0.015-0.025, advantageously 0.019-0.023; Boron: 0.01-0.02; Nickel: balance; and unavoidable impurities; and preferably consisting essentially of, and especially consisting of, a tantalum-free composition comprising:

[0042] In particular, the composition of the superalloy according to the present invention may be as shown in Table 1 below.

[0043] [Table 1]

[0044] In an advantageous embodiment, the superalloy according to the invention has a strength of 8500 kg / m 3 less than, advantageously 8300 kg / m 3 Therefore, the density of the superalloy of Example 1 is 8240 kg / m 3 The volume is measured using a helium pycnometer and the mass is measured using a precision balance, and then these two measurements are used to calculate the density.

[0045] In another advantageous embodiment, the superalloy according to the invention has metallurgical stability (in other words, absence of TCP phase - topologically compact phase) up to 800-850°C.

[0046] In yet another advantageous embodiment, the superalloy according to the invention has good oxidation resistance.

[0047] In another advantageous embodiment, the superalloy of the present invention has a difference between the gamma prime solvus temperature and the combustion temperature that is sufficiently large for performance in supersolvus processing, advantageously a difference of at least 15° C. Thus, the gamma prime solvus temperature of the superalloy of Example 1 is 1195° C. and its combustion temperature is 1210° C.

[0048] The invention further relates to the superalloy powder according to the invention.More specifically, the superalloy according to the invention can be found in the form of a powder having a particle size distribution between 10 μm and 100 μm.

[0049] The present invention further relates to a method for producing a powder of the nickel-base superalloy according to the present invention, comprising the steps of: A - Mixing raw or pre-alloyed raw materials; B—melting the mixture obtained in step A), advantageously in a vacuum induction furnace (VIM); C—gas atomization, advantageously with argon, of the product obtained in step B), so as to obtain a powder advantageously of predominantly spherical shape (in other words without sharp corners); D - sieving the powder obtained in step C), advantageously under an inert atmosphere, to obtain the desired particle size distribution; E - Collecting the resulting powder.

[0050] Thus, the particle size distribution of the powder is determined and adopted depending on the technology for manufacturing superalloy powder-based components envisaged. The range of particle size distributions applied in the various manufacturing methods varies depending on the technology, the equipment and the intended application. Generally, for all applications, the powders used in these methods will have a more or less broad number size distribution between 10 μm and 100 μm.

[0051] The present invention further provides a method for producing a component, in particular a turbine component, made from a superalloy according to the invention or made from a superalloy powder according to the invention, comprising the following steps: a-forging, b - Gradient heat treatment of the part obtained in step a), c) final heat treatment of the entire double microstructure part obtained in step b); d - Recovery of the parts obtained in step c), The present invention relates to a manufacturing method comprising the steps of:

[0052] The forging step a) can be carried out by methods well known to those skilled in the art, including, for example, extrusion, in particular hot extrusion, rolling, die forging (such as isothermal forging), drop forging, drawing and / or combinations of these techniques, which are well known to those skilled in the art. This step a) allows a part made of a superalloy to be obtained.

[0053] The gradient heat treatment step b) can be carried out using the method and equipment described in patent application FR 3043410.

[0054] The process may also include heating a region of the component to a first temperature (T1) that is at least 5°C above the solvus temperature of the gamma prime phase of the superalloy and below the melting temperature of the superalloy (thus comprising supersolvus processing).

[0055] The gradient heat treatment can be carried out, for example, by local induction heating or by any of the methods or devices described in patent application FR 3043410.

[0056] If the component is a turbine disk, the area of ​​the component exposed to the first temperature (T1) comprises the rim area of ​​the disk, with the remainder of the component being unaffected by the treatment.

[0057] Thus, to increase the grain size and suppress or improve creep and cracking while effectively maintaining the hardened state at high temperatures (even withstanding temperature peaks of 800°C or 850°C), a supersolvus treatment (temperature T1) can be performed, which fully utilizes the hardening ability associated with the gamma prime phase. Therefore, the grain size is advantageously 15 μm or larger (measured by the intercept method). Furthermore, to maintain good fatigue resistance, an average grain size of 40 μm is advantageous.

[0058] Step b) allows for the production of components with a dual or gradient microstructure, i.e., components that do not have a homogeneous microstructure, but in which the size of the grains in particular is not the same depending on whether the grains are in the areas of the component that have been subjected to the supersolvus treatment or in the areas of the component that have not been subjected to the supersolvus treatment. Thus, the components contain coarse grains and fine grains, advantageously with a size of 15 μm or more, for example in the rim of the disk, and forging-derived fine grains with a size of less than 15 μm, for example in the bore of the disk. The grain size is measured by the intercept method.

[0059] Step c) of the method according to the invention may comprise the following successive steps: c1—Solution heat treating the entire part obtained in step b) at a temperature (T2) below the solvus temperature of the gamma-prime phase of said superalloy (thus it comprises a sub-solvus treatment). c2—Quenching the entire part obtained in step c1); advantageously, the quenching speed is adapted to the mass of the part in order to obtain an optimal size and distribution of the gamma prime hardening phase. c3--Tempering the entire part obtained in step c2), advantageously at a temperature higher than 760°C.

[0060] The final heat treatment in step c) is therefore a conventional heat treatment carried out on gamma / gamma-prime alloys. The purpose of this treatment is to treat the structures not affected by the gradient treatment in order to obtain a final structure in these regions with mechanical properties corresponding to the desired level. More specifically, in the regions that have only been subjected to the sub-solvus treatment (temperature T2), the grain size remains low, advantageously less than 10 μm (measured by the intercept method), which allows good tensile and fatigue properties to be obtained at moderate temperatures, for example below 750°C.

[0061] In particular, step c3) can consist of one or two tempering stages.

[0062] Therefore, a relatively high temperature final tempering treatment (>760°C) stabilizes the microstructure of the component at high temperatures and relieves residual stresses resulting from quenching and treatment at temperature T2.

[0063] Tempering and quenching are carried out using techniques well known to those skilled in the art.

[0064] The invention also relates to a part made of the superalloy according to the invention or made of the superalloy powder according to the invention, having a duplex microstructure, advantageously obtained by the method according to the invention, which is advantageously a turbomachine part, more advantageously a turbine part, in particular a turbine disk, compressor disk, ring, flange or turbine housing.

[0065] The component according to the invention thus has a dual or gradient microstructure, i.e., it is not a homogeneous microstructure. In particular, the grain size of the component varies in different regions of the component. Accordingly, the component contains coarse and fine grains, with coarse grains preferably having a size of 15 μm or more, preferably an average of 40 μm, and fine grains having a size of less than 15 μm. Thus, if the component is a turbine disk, the rim region of the disk preferably has coarse grains having an average size of 15 μm or more, preferably an average of 40 μm, and the bore region of the disk preferably has fine grains having a size of less than 15 μm. The grain size is measured by the intercept method.

[0066] Advantageously, the coarse-grained region of the component has good creep resistance at a temperature of 800°C in accordance with standard NF EN ISO 204 August 2009, and more advantageously exhibits an elongation of up to 0.2% at a temperature of 750°C under a stress of 500 MPa for a duration of more than 160 hours, in particular more than 170 hours, and even more particularly more than 175 hours. This region can still withstand temperatures increased to 850°C as well.

[0067] Advantageously, the fine-grained region of the component has a good breaking strength in accordance with standard NF EN 2002-001 / 06 at temperatures below 750°C, in particular an elastic modulus of greater than 1150 MPa at 20°C.

[0068] The present invention will be better understood by reference to the following illustrative examples, which are given by way of example and not by way of limitation. [Example]

[0069] A nickel-based superalloy according to the present invention (Example 1) was produced according to the following method: an ingot was vacuum cast, then the ingot was atomized under argon, sieved to a size of 53 μm, the powder was placed in a container while degassing, and then the powder was hot extruded into rods. The density of the alloy was measured to be 8240 kg / m3 The volume was measured by helium pycnometry, and the mass was measured using a precision balance, and the density was calculated using these two measurements. The alloy contained 56.5% gamma prime phase.

[0070] The alloys produced have the chemical compositions (mass %) shown in Table 1 above.

[0071] The solvus temperature of the gamma prime phase of this alloy is 1195°C.

[0072] A portion of the bar was then subjected to a 2-hour treatment at 1200°C, i.e., above 1195°C (supersolvus treatment), followed by cooling at 30°C / min, a 2-hour treatment at 1165°C, i.e., below 1195°C (subsolvus treatment), followed by a 100°C / min quench and then a 8-hour tempering at 800°C, i.e., above 760°C (representing the thermal cycle of the disc rim region). The resulting microstructure showed an intercept grain size of 24 μm, measured on the sample surface by EBSD imaging (Electron Back Scattered Diffraction), which is larger than 15 μm.

[0073] Another portion of the bar was subjected to only the secondary solvus treatment, followed by a quench and temper treatment, both at the same temperature and for the same time as the first portion of the bar (representative of the thermal cycle in the bore region of the disk). The grain size in this microstructure, as measured by the intercept method, is 3.5 μm, which is less than 15 μm.

[0074] Tensile and creep tests were carried out on samples taken from these two bars according to the standard NF EN 2002-001 / 06 and the standard NF EN ISO 204 August 2009, respectively.

[0075] The results obtained were compared with prior art compositions produced by powder metallurgy and homogeneous heat treatment, having compositions in weight percent as shown in Table 2 below.

[0076] [Table 2]

[0077] The results of the tensile tests (elastic limit and mechanical strength as a function of temperature) are shown in Figures 1 and 2.

[0078] The creep results are shown in Table 3 below.

[0079] [Table 3]

[0080] The tensile results of the alloy of the present invention (Example 1) are close to or better than those of alloy ME501 and alloy A (both of which are tantalum-bearing). The tensile results are also better than those of SMO43(N19), with the alloy benefiting from density. More specifically, the density of SMO43(N19) is 8340 kg / m 3 Furthermore, the alloys of the present invention undergo a relatively high temperature final temper (>760°C) compared to alloys SMO43 (final temper at 750°C) and ME501 (final temper at 760°C) to stabilize the microstructure at high temperatures, but at the expense of a slight decrease in tensile strength and creep resistance. The solid squares and circles in Figures 1 and 2 represent the mechanical properties of the parts after the duplex process as a function of the operating temperature observed in each region (the transition is located at 750°C). The fine-grained region (solid squares) exhibits optimal resistance to temperatures below 750°C, while the coarse-grained region (solid circles) exhibits optimal resistance to temperatures above 750°C.

[0081] The elongation creep results show good resistance for the alloy according to the invention, despite the finer grain size and higher tempering temperature than SMO 43. The alloy can also withstand transfer to very high temperatures such as 850°C. Some embodiments of the present invention are described in the following items [1]-

[12] . [1] A nickel-base superalloy having a composition, in percent by weight of the total composition, of: Chromium: 10.0-11.25, advantageously 10.0-11.0; Cobalt: 11.2-13.7, advantageously 12.0-13.0; Molybdenum: 3.1-3.8, advantageously 3.3-3.7; Tungsten: 3.1-3.8, advantageously 3.1-3.5; Aluminum: 2.9-3.5, advantageously 3.2-3.5; Titanium: 4.6-5.6, advantageously 4.6-5.0; Niobium: 1.9-2.3, advantageously 1.9-2.0; Hafnium: 0.25-0.35, advantageously 0.25-3.0; Zirconium: 0.040-0.060, advantageously 0.050-0.060; Carbon: 0.010-0.030, advantageously 0.015-0.025; Boron: 0.01-0.030, advantageously 0.01-0.02; Nickel: balance; and unavoidable impurities; 1. A nickel-base superalloy characterized in that it is a tantalum-free composition comprising, and advantageously consisting essentially of, [2] 2. The nickel-based superalloy according to item 1, characterized in that the volume fraction of the gamma prime phase is 52% to 60%. [3] 3. The nickel-based superalloy according to item 2, wherein the sum of the contents of Al, Ti, and Nb is 13 to 15 atomic percent. [4] 4. The nickel-based superalloy according to item 2 or 3, characterized in that the ratio of the contents of the elements, (Ti+Nb) / Al, is less than 1.2 in atomic %. [5] 5. The nickel-based superalloy according to any one of items 1 to 4, wherein the sum of the contents of W, Mo, Cr and Co is 25.5 to 29.5 atomic %. [6] 6. The nickel-based superalloy according to any one of items 1 to 5, wherein the sum of the contents of W and Mo is 2.3 to 3.9 atomic percent. [7] 7. A superalloy powder according to any one of items 1 to 6. [8] The following steps: a-forging, b - Gradient heat treatment of the part obtained in step a), c--final heat treatment of the entire double microstructure part obtained in step b); d - Recovering said parts obtained in step c), 8. A method for producing a part made of the superalloy according to any one of items 1 to 6 or made of powder of the superalloy according to item 7, comprising: [9] A step b) of gradient heat treating the part obtained in step a), b1—heating a region of the component at a first temperature (T1) that is greater than the solvus temperature of the gamma prime phase of the superalloy and less than the melting temperature of the superalloy (first heat).

[10] Step c) of final heat treatment The following sequential steps: c1 - solution heat treatment of the entire component obtained in step b) at a temperature (T2) lower than the solvus temperature of the gamma prime phase of said superalloy; c2 - quenching the entire part obtained in step c1); c3 - tempering the entire part obtained in step c2), advantageously at a temperature higher than 760 ° C; 10. The method according to item 8 or 9, comprising:

[11] 11. A part having a dual microstructure and made of the superalloy according to any one of items 1 to 6, or made of the superalloy powder according to item 7, advantageously obtained by the method according to any one of items 8 to 10.

[12] 12. The component according to item 11, characterized in that it is a turbomachine component, advantageously a turbine component, in particular a turbine disk, a compressor disk, a ring, a flange or a turbine housing.

Claims

1. A nickel-base superalloy having a composition, in percent by weight of the total composition, of: Chromium: 10.0-11.25; Cobalt: 11.2-13.7; Molybdenum: 3.1-3.8; Tungsten: 3.1-3.8; Aluminum: 2.9-3.5; Titanium: 4.6-5.6; Niobium: 1.9-2.3; Hafnium: 0.25-0.35; Zirconium: 0.040-0.060; Carbon: 0.010-0.030; Boron: 0.01-0.030; nickel: balance; and Inevitable impurities; and wherein the nickel-based superalloy is a tantalum-free composition.

2. The nickel-base superalloy of claim 1, wherein the volume fraction of gamma prime phase is between 52% and 60%.

3. 3. The nickel-based superalloy according to claim 2, wherein the sum of the contents of aluminum, titanium and niobium is 13 to 15 atomic percent.

4. A nickel-based superalloy according to claim 2 or 3, characterized in that the ratio of the contents of the elements (titanium + niobium) / aluminum is less than 1.2 in atomic %.

5. 5. The nickel-based superalloy according to claim 1, wherein the sum of the contents of tungsten, molybdenum, chromium and cobalt is 25.5 or more and 29.5 or less in atomic percent.

6. 6. The nickel-based superalloy according to claim 1, wherein the sum of the contents of tungsten and molybdenum is 2.3 to 3.9 atomic percent.

7. The superalloy powder according to any one of claims 1 to 6.

8. The following steps: a - forging a powder of the superalloy according to any one of claims 1 to 6 or of the superalloy according to claim 7; b- Gradient heat treatment of the part obtained in step a) to form a dual microstructure part; c--final heat treatment of the entire dual microstructure part obtained in step b) to form the final part; d - Recovering the final part obtained in step c), 8. A method for producing a part made of a superalloy according to any one of claims 1 to 6 or made of a powder of a superalloy according to claim 7, characterized in that it comprises

9. A step b) of gradient heat treatment of the part obtained in step a), 10. The method of claim 8, comprising: b1—heating a region of the component at a first temperature (T1) that is greater than the solvus temperature of the gamma prime phase of the superalloy and less than the melting temperature of the superalloy (first heat).

10. Step c) of final heat treatment The following consecutive steps: c1 - solution heat treatment of the entire component obtained in step b) at a temperature (T2) below the solvus temperature of the gamma prime phase of said superalloy; c2 - quenching the entire part obtained in step c1); c3 - tempering the entire part obtained in step c2); 10. The method according to claim 8 or 9, characterized in that it comprises:

11. A component made from the superalloy of any one of claims 1 to 6 or made from the superalloy powder of claim 7, having a duplex microstructure.

12. 12. The component according to claim 11, characterized in that it is a turbomachinery component.

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