Heat treatment process for a single-material blade

Abstract

Heat treatment process for a single-material metal turbine blade. Heat treatment process for a single-material metal turbine blade (1) comprising: - a first heat treatment carried out on a first part (2) of the blade (1) at a first temperature TA, for a first time tA, and - a second heat treatment carried out on a second part (3) of the blade (1) at a second temperature TB, for a second time tB, the first and second heat treatments being carried out simultaneously, the first and second temperatures TA, TB and the first and second times tA, tB being adapted to modify the size of the precipitates γ' in at least the first or second part (2, 3) of the blade (1). Figure for the abstract: Fig. 1.

Description

Title of the invention: Heat treatment process for a single-material blade. Technical field

[0001] The present exposition relates to the general field of aircraft and more particularly to a heat treatment process for a single-material metallic turbine blade.

[0002] Such a method can, for example, be used to optimize the mechanical performance of metal turbomachine distributor blades. Such blades are particularly suitable for applications in high-pressure turbines and compressors. Previous technique

[0003] With the aim of increasing the performance of turbine blades, the goal is to reduce the mass of the blades by optimizing the properties of the materials. This results in a significant reduction in the overall mass of the rotating and stationary parts of the turbomachinery and ultimately an increase in aircraft performance.

[0004] The blade is a complex part whose different parts have very different operating points.

[0005] For solid blades, the blade operates in fine-tuning often at high temperature (typically above 800°C) while the foot operates in fatigue at cold (typically around 800°C).

[0006] For cooled hollow blades, the blade operates in fatigue / creep coupling with a strong thermal gradient between the inside and outside while the foot operates in cold fatigue (typically around 800°C).

[0007] The blades are formed from a nickel-based superalloy having an austenitic matrix y with precipitation of the y' phase, generating a microstructure of type yIy', generally single-crystal.

[0008] The optimization of the mechanical properties of the blades is notably obtained by a heat treatment.

[0009] Heat treatment processes for single-material blades conventionally include a microstructure solution treatment step to dissolve residual eutectics from solidification, homogenize the chemical composition at the dendritic scale, and dissolve precipitates y' from solidification by exceeding the solvus temperature while avoiding exceeding the burn temperature. New precipitates y' appear during a quenching operation.

[0010] The heat treatment processes for single-material blades also include successive tempering to obtain precipitates of cubic structure y' having a desired shape and size.

[0011] These main steps are carried out in a conventional furnace under controlled atmosphere (partial pressure in neutral gas) or secondary vacuum.

[0012] Primary precipitates form during the solidification of the alloy and are partially or totally dissolved during solution heating. Secondary precipitates form at the end of the solution heating step, during quenching. Tertiary precipitates form at the end of the tempering heat treatment step.

[0013] The average size of the precipitates y' is classically targeted at 400nm with a dispersion between 300nm and 700nm.

[0014] Recent publications show that a population of tertiary γ' precipitates smaller in size (on the order of a few tens of nanometers) than those of primary and secondary precipitates can offer advantages in terms of mechanical properties. A blade with a higher γ' precipitate population than primary and secondary precipitates is therefore desirable.

[0015] However, the cooling rate during quenching at the end of the solution treatment can vary depending on the blade thickness, which is sometimes not uniform along its entire length, resulting in a non-uniform size of precipitates y' along the blade. Therefore, there is a need to standardize the size of the precipitates y' throughout the entire blade.

[0016] Conversely, in other cases, the blade obtained after dissolution may exhibit a uniform precipitate size y' along its entire length. However, for certain applications, it is desirable to obtain heterogeneous precipitate sizes y' along the blade's length, i.e., a blade exhibiting a larger precipitate size y' on one portion of the blade than on a second portion. Therefore, there is a need to obtain heterogeneous precipitate sizes y' at the part scale.

[0017] However, there is no method to control the size of the precipitates y' over the entire length of a blade in order to obtain optimal mechanical properties according to the parts of the blade stressed. Description of the invention

[0018] The present invention aims to remedy in whole or in part the aforementioned problems of the prior art by proposing a heat treatment method for a single-material aircraft turbojet blade allowing control of the size and distribution of the precipitates y' more finely and locally over the entire length of the blade.

[0019] The invention relates to a heat treatment process for a single-material turbomachine blade made of a metallic alloy comprising: - a first heat treatment carried out on a first part of the blade at a first temperature TA, for a first time tA, and - a second heat treatment carried out on a second part of the dawn at a second temperature TB, for a second time tB, the first and second heat treatments being carried out at least partly simultaneously, the first and second temperatures TA, TB and the first and second times tA> tB being adapted to modify the size of the precipitates y' in at least the first or second part of the dawn.

[0020] The invention thus provides a heat treatment method for a single-material aircraft turbojet blade allowing control of the size and distribution of the y' precipitates more finely and locally in the blade.

[0021] This heat treatment process is applied during tempering, after solution treatment and quenching of the blade.

[0022] During the heat treatment process, the heating and cooling of the two parts are controlled separately, allowing two distinct parts of the same blade with different properties to be heat treated, with two heat treatments each adapted for one of these parts.

[0023] This makes it possible to obtain a microstructure y / y' independent of the heat treatment of solution treatment and associated quenching.

[0024] The heat treatment process makes it possible to obtain a microstructure y / y' adapted to each part of the blade and which is a function of its use and the mechanical properties sought for that part.

[0025] This type of blade, featuring two different microstructures, provides performance and mass gains and increased service life.

[0026] In some embodiments, the first time tA and the second time tB are identical, the first temperature TA being different from the second temperature TB.

[0027] In some embodiments, the first time tA and the second time tB are different, the first temperature TA being equal to the second temperature TB.

[0028] In some embodiments, the first time tA and the second time tB are different, the first temperature TA being different from the second temperature TB.

[0029] In some embodiments, superheating is applied to the first part and / or the second part of the blade at a temperature T' between the solvus temperature and the burning temperature of the blade alloy.

[0030] In certain embodiments, the first and second parts comprise, before the application of the first and second heat treatments, precipitates y' presenting an identical average size. The first and second temperatures TA, Tb and the first and second times tA, tB are adapted to obtain precipitates y' of different average sizes in the first and second parts.

[0031] In certain embodiments, the first and second parts comprise, prior to the application of the first and second heat treatments, precipitates y' of different average sizes. The first and second temperatures TA, TB and the first and second times tA, tB are adapted to obtain precipitates y' of identical average size in the first and second parts.

[0032] In some embodiments, the first temperature TA is between 1170 °C and 1300 °C and the second temperature TB is between 890 °C and 1170 °C.

[0033] In some embodiments, the process comprises: • a positioning step of the first part of the metal blade in a first chamber of a furnace configured to maintain the first part at the first temperature TA, and • a positioning step of the second part of the metal blade in a second chamber of the furnace configured to maintain the second part at the second temperature TB.

[0034] The invention also relates to a single-material metallic turbine blade obtained by the heat treatment process as defined above.

[0035] The aforementioned features and advantages, as well as others, will become apparent from the following detailed description, examples of embodiments of the proposed device and method. This detailed description refers to the accompanying drawings. Brief description of the drawings

[0036] The attached drawings are schematic and are intended primarily to illustrate the principles of the exposition.

[0037] On these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs.

[0038] [Fig-1] The [Fig. 1] schematically represents an oven for implementing the process according to one embodiment of the invention;

[0039] [Fig.2] Fig.2 represents the evolution of the temperature perceived by the first and the second part of the metal blade as a function of time, according to a first embodiment of the process of the invention;

[0040] [Fig.3] Fig.3 represents the evolution of the temperature perceived by the first and second part of the metal blade as a function of time, according to a second embodiment of the process of the invention;

[0041] [Fig.4] Fig.4 represents the evolution of the temperature perceived by the first and the second part of the metal blade as a function of time, according to a third embodiment of the process of the invention;

[0042] [Fig. 5] Fig. 5 represents the evolution of the temperature perceived by the first and the second part of the metal blade as a function of time, according to a fifth embodiment of the process of the invention. Description of the implementation methods

[0043] The invention relates to a heat treatment method for a single-material metallic blade 1 of an aircraft turbomachine.

[0044] The blade 1 is formed of a nickel-based superalloy having an austenitic matrix y with precipitation of the y' phase, generating a microstructure of type yIy', generally single-crystal.

[0045] The blade alloy 1 can be a commercial alloy CMSX-4® or AMI, for example.

[0046] After obtaining the blade 1 in the foundry, the blade 1 undergoes preliminary heat treatments including, for example, a step of dissolving the microstructure to dissolve the residual eutectics from solidification, homogenize the chemical composition at the dendritic scale and dissolve y' precipitates from solidification by exceeding the solvus temperature while avoiding exceeding the burn temperature.

[0047] A quenching process is then carried out. New precipitates y' appear during the quenching, forming an alloy with a microstructure y / y'.

[0048] According to the invention, the heat treatment process then comprises two simultaneous heat treatments, of which a first heat treatment is carried out on a first part 2 of the blade 1 at a first temperature TA, for a first time tA, and a second heat treatment is carried out on a second part 3 of the blade 1 at a second temperature TB, for a second time tB.

[0049] The first and second heat treatments are carried out simultaneously in the same oven 100.

[0050] Fig. 1 represents the oven 100 which is suitable for implementing the process of the invention.

[0051] The furnace 100 comprises a first chamber 10 configured to maintain the first part 2 of the vane 1 at the first temperature TA and a second chamber 12 configured to maintain the second part 3 of the vane 1 at the second temperature Tb. A separating screen 11 separates the first chamber 10 and the second chamber 12. In this example, the first chamber 10 is said to be "hot" and the second chamber 12 is said to be "cold" because the temperatures applied are lower in the The second chamber 12 is suitable for heating materials by convection or induction. For example, conventional heating is used in the first chamber 10 and induction heating is used in the second chamber 12.

[0052] The separation screen 11 is thermally insulating. For example, the separation screen 11 can maintain a temperature difference between the first enclosure 10 and the second enclosure 12 greater than 2°C, for a separation screen 11 having a thickness greater than 1mm, for example.

[0053] The metal blade 1 is arranged in the furnace 100 with the first part 2 of the blade 1 positioned in the first enclosure 10 of the furnace 100 and the second part 3 of the blade 1 positioned in the second enclosure 12 of the furnace 100. For example, the first part 2 may correspond to the blade of the blade 1 and the second part 3 may correspond to the foot of the blade 1.

[0054] It should be noted that the reverse configuration is also feasible, so that the first part 2 is disposed in the cold enclosure 12 and the second part 3 is disposed in the hot enclosure 10.

[0055] In the example of [Fig. 1], the nozzle 1 includes a transition zone 4 which may correspond to the platform of the nozzle 1. The transition zone 4 separates the first part 2 from the second part 3 of the nozzle 1, which are composed of the same material but have different microstructures. The transition zone 4 corresponds to the boundary between the two microstructures. The first part 2 may contain more Tertiary γ' precipitates than the second part 3, for example.

[0056] In the present embodiment, the blade 1 has a simplified rectangular shape to facilitate illustration.

[0057] The intermediate part 4, corresponding to the middle of the blade 1 in this example, is positioned in the same plane as the separating screen 11 of the furnace 100 so that the blade 1 has a first proportion (first part 2) placed in the first enclosure 10 which is identical to a second proportion of blade 1 (second part 3) placed in the second enclosure 12. Other positionings are possible such as a first proportion of blade 1 placed in the first enclosure 10 greater than a second proportion of blade 1 placed in the second enclosure 12.

[0058] The furnace 100 may include a cooling system comprising a chamber under controlled pressure or vacuum, for example. This chamber may be cooled using a gas, typically an inert gas such as argon.

[0059] Alternatively, the cooling system may include a chamber configured to receive a liquid in which the second part 3 of the blade 1 can be immersed. In order to achieve cooling, the cooling chamber may include a liquid, typically a liquid metal such as liquid aluminum.

[0060] Alternatively, the cooling system may include a footprint (tooling) configured to hold the second part 3. The footprint is cooled, and may for example include a water or cryogenic gas cooling circuit.

[0061] Thus, the two parts 2, 3 of the blade 1 can simultaneously undergo two different heat treatments in the furnace 100. The two chambers 10, 12 of the furnace 100 can be controlled differently in terms of temperature and heat treatment time. Heating and cooling can be controlled separately for each part 2, 3 of the blade 1.

[0062] The two heat treatments applied to the blade 1 are heat treatments allowing the size of the precipitates y' to be modified simultaneously in the first part 2 and / or the second part 3 of the metallic blade 1.

[0063] The average size of the precipitates y' can be estimated by the time / temperature pair according to a ripening-type law:

[0064]

[0065] Where:

[0066] M?') is a parameter of the model which is a function of the temperature T and which is an exponential relationship such as k(T) = Aexp(AT), for example, dependent on each alloy,

[0067] (y) represents the average size of the precipitates after heating at a temperature T, for a duration f,

[0068] ( Æy ) represents the average size of precipitates before income.

[0069] The average size of the precipitates y' in each part 2, 3 of dawn 1 can be estimated according to the following relationships:

[0070] (“y) 3=(ay)3 + Aexp(ÀTA) • tA / 1 ( M ? = < a Y ) o + Aexp ( ' ( B

[0071] The average size of the y1 precipitates, when the alloy comprises only primary and secondary y1 precipitates, is about 400nm with a dispersion between 300nm and 700nm.

[0072] Tertiary y1 precipitates have smaller dimensions (on the order of a few tens of nanometers) than primary y1 precipitates, which have a size between 300nm and 800nm, and secondary y1 precipitates, which have a size between 300nm and 800nm.

[0073] Fig. 2 represents the evolution of the temperature T perceived by the first part 2 and the second part 3 of the blade 1 as a function of time t, for a heat treatment process according to a first embodiment of the invention.

[0074] The first heat treatment and the second heat treatment are carried out for identical durations (tA = tB) and at different temperatures (TA TB).

[0075] In this example, the first temperature TA applied to the first part 2 of the dawn 1 is greater than the second temperature Inapplicated to the second part 3 of the dawn 1.

[0076] The first temperature TA is between a minimum temperature TAmin which can be about 1170°C and a maximum temperature TAmax which can be about 1300°C, for example.

[0077] The second temperature TB is between a minimum temperature TBmin which can be about 870°C and a maximum temperature TBmax which can be about 1170°C, for example.

[0078] Both temperature curves exhibit a temperature rise with an identical slope, each followed by a plateau P1, P2, and then a temperature drop with an identical slope. The plateaus P1, P2 are constant and of the same duration.

[0079] Every material has a solvus temperature and a burn temperature. To obtain satisfactory heat treatment for a material, it must be heated above its solvus temperature but below its burn temperature. Indeed, above the burn temperature, the material degrades and begins to melt.

[0080] The first temperature TA can be between the solvus temperature (TAmin) and the burn temperature (Ta™,») of the blade alloy 1, for example.

[0081] In a first case, if the size of the precipitates y' is initially homogeneous in the first part 2 and the second part 3 of the dawn 1 ({a,')3 = {a'Ÿ X the heat treatment process has the effect of generating a heterogeneous size of precipitates y' in the first part 2 and the second part 3 of the dawn 1 ( ( ) 3 ( dy ) 3)-

[0082] The term “initially” means an observation made “before the application of the first and second heat treatments”.

[0083] For example, for an AMI alloy initially exhibiting precipitates y' of identical size in both parts 2 and 3, a "bleaching" of the microstructure of the first part 2 at a first temperature TA of 1300°C for a time tA of approximately 1 hour results in the formation of more tertiary precipitates y', and therefore smaller precipitates y', in the first part 2 than in the second part 3 of the blade 1. The second part 3 of the blade 1 undergoes a second treatment thermal at a temperature TB of approximately 900°C for a time tB of 1 hour approximately also because it is not desirable to form tertiary precipitates in the Part 2, 3.

[0084] In a second case, if the size of the precipitates y' is initially heterogeneous in the first part 2 and second part 3 of dawn 1)' 'c process of heat treatment has the effect of generating a homogeneous precipitate size y' in the first part 2 and in the second part 3 of dawn 1 ( / £ / a 3= / # A 3). ' y'A xy 'B

[0085] For example, for an AMI alloy initially exhibiting precipitates y' of different sizes in the two parts 2, 3, i.e., only tertiary y' precipitates in the second part 3 and larger y' precipitates in the first part 2, a "bleaching" of the microstructure of the first part 2 at a first temperature TA of 1300°C for a time tA of approximately 1 hour has for The effect is to form tertiary precipitates y', and therefore smaller precipitates y', in the first part 2 so as to obtain the same size of precipitates y' in the first part 2 as in the second part 3. The second part 3 of dawn 1 undergoes a second heat treatment at a temperature TB of approximately 900°C for a time tB of approximately 1 hour also because it is not desired to modify the size of the precipitates y' in the second part 3.

[0086] Fig. 3 represents the evolution of the temperature T perceived by the first part 2 and the second part 3 of the blade 1 as a function of time t, for a heat treatment process according to a second embodiment of the invention.

[0087] The first heat treatment and the second heat treatment are carried out for different durations (tA tB) and at identical temperatures (TA = TB).

[0088] In this example, the first temperature TA applied to the first part 2 of dawn 1 is therefore identical to the second temperature Inapplicated to the second part 3 of dawn 1, but for a first time tA longer than the second time 1b-

[0089] Both temperature curves show a temperature rise with an identical slope followed by a plateau PI, P2, and then a temperature fall with an almost identical slope. The plateaus PI, P2 are constant and at the same temperature, but the first plateau PI at the first temperature TA lasts longer than the second plateau P2 at the second temperature TB.

[0090] In a first case, if the size of the precipitates y' is initially homogeneous in the first part 2 and the second part 3 of the dawn 1 = (a ), the process of heat treatment has the effect of generating a heterogeneous precipitate size y' in the first part 2 and the second part 3 of dawn 1 ( / A 3 / aa 3). V y ' A ' y ' B

[0091] A longer heat treatment time will tend to promote growth of precipitates y' tertiary in one of parts 2, 3.

[0092] In a second case, if the size of the precipitates y' is initially heterogeneous in the first part 2 and second part 3 of dawn 1 (laA3 * (a A3 ), this treatment thermal has the effect of generating a more homogeneous size of precipitates y' in the first part 2 and the second part 3 of dawn 1 ( / ^ .\ 3— (d ,\ 3). 'Y'A 'Y'B

[0093] The longer heat treatment time will tend to favor the growth of tertiary y' precipitates in one of the parts 2, 3 which initially had less or no tertiary y' precipitates.

[0094] Fig. 4 represents the evolution of the temperature T perceived by the first part 2 and the second part 3 of the blade 1 as a function of time t, for a heat treatment process according to a third embodiment of the invention.

[0095] The first heat treatment and the second heat treatment are carried out for different durations (tA tB) and at different temperatures (TA TB).

[0096] In this example, the first temperature TA applied to the first part 2 of dawn 1 is higher than the second temperature Inapplied on the second part 3 of dawn 1 and for a first time tA longer than the second time tB.

[0097] The first temperature TA is between a minimum temperature TAmin which can be about 1170°C and a maximum temperature TAmax which can be about 1300°C, for example.

[0098] The second temperature TB is between a minimum temperature TBmin which can be about 870°C and a maximum temperature TBmax which can be about 1170°C, for example.

[0099] The two temperature curves exhibit a temperature rise with an identical slope, each followed by a plateau P1, P2, and then a temperature drop with an almost identical slope. The plateaus P1, P2 are constant but not at the same temperature and are not of the same duration. The first plateau P1, which is at the first temperature Ta, lasts longer than the second plateau P2, which is at the second temperature TB.

[0100] In a first case, if the size of the precipitates y' is initially homogeneous in the first part 2 and the second part 3 of dawn 1 h the process of ^B Heat treatment has the effect of generating a heterogeneous precipitate size y' in the first part 2 and the second part 3 of dawn 1 ( / a . \ (d \ ^)- 'Y A 1 y>B

[0101] The longer heat treatment time will tend to favor the growth of tertiary y' precipitates in one of the parts 2, 3.

[0102] In a second case, if the size of the precipitates y' is initially heterogeneous in the first part 2 and second part 3 of dawn 1 ( / a ■ )3 £ ( a ■ V3 ), the process of ' ' >' / oB heat treatment has the effect of generating a homogeneous precipitate size y' in the first part 2 and the second part 3 of dawn 1 ( / y A 3 — / A 3). ' v ' A ' ■ ' B

[0103] By simultaneously playing on the temperatures TA and TB as well as on the durations tA and tB, it is possible to control the distribution of the size of the precipitates y' in addition to the size of the precipitates y'.

[0104] Fig. 5 represents the evolution of the temperature T perceived by the first part 2 and the second part 3 of the blade 1 as a function of time t, for a heat treatment process according to a fourth embodiment of the invention.

[0105] The first heat treatment and the second heat treatment are carried out for identical durations (tA = tB) and at different temperatures (TA TB).

[0106] In this example, the first temperature TA applied to the first part 2 of dawn 1 is on average higher than the second temperature Inapplicable to the second part 3 of dawn 1.

[0107] Unlike the embodiment of [Fig.2], superheating is applied to the first part 2 of the blade 1 at a temperature T' in the first chamber 10 of the furnace 100.

[0108] The first temperature TA evolves over time, starting with a sharp rise until it reaches temperature T' for a short time t', less than half of the first time tA. The time t' can be 1 hour, for example, for a total initial time tA of 4 hours.

[0109] The first temperature TA then falls back to a first plateau PI which remains constant until the first temperature TA falls again. In the first plateau PI, the first temperature TA is between a minimum temperature TAmin which can be about 1170°C and a maximum temperature TAmax which can be about 1300°C, for example.

[0110] The second temperature TB is between a minimum temperature TBmin which can be about 870°C and a maximum temperature TBmax which can be about 1170°C, for example.

[0111] The temperature T' is strictly greater than the second temperature TB and the temperature of the first plateau PL. The temperature T' is between the solvus temperature and the burning temperature of the blade alloy 1.

[0112] Preferably, the temperature T' is close to the solvus temperature of the blade alloy 1. For example, the temperature T' can be more or less 5°C from the solvus temperature.

[0113] The second temperature TB evolves over time, starting by rising and reaching a plateau P2 which is constant until a decrease in temperature.

[0114] Alternatively, the superheating can be applied in the middle or at the end of the first heat treatment, for example.

[0115] Overheating to a temperature close to the solvus of the alloy for a limited time allows the formation of a tertiary y' precipitation.

[0116] For example, it is possible to achieve a "bleaching" of the microstructure of the first part 2 of an AMI alloy by raising the superheating temperature T' to 1300°C for a time t' of approximately 1 hour.

[0117] Alternatively, if precipitation of tertiary precipitate y' is desired while preserving secondary precipitates for an AMI alloy, the superheating temperature T' is raised to 1300°C, or a little less (1250°C), for a time t' of a few minutes.

[0118] Alternatively, an identified induction heater is used in the first and second chambers 10, 12, which allows for better targeting of the heating zone. The temperature range to be achieved is lower (between 890°C and 1170°C) for each of the two parts 2, 3 of the nozzle 1 in the case where tertiary precipitation is not desired.

[0119] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0120] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Demands

1. Heat treatment process for a single-material turbomachine blade (1) made of a metal alloy, characterized in that the process comprises: - a first heat treatment carried out on a first part (2) of the blade (1) at a first temperature TA, for a first time tA, and - a second heat treatment carried out on a second part (3) of the blade (1) at a second temperature TB, for a second time tB, the first and second heat treatments being at least partly carried out simultaneously, the first and second temperatures TA, TB and the first and second times tA, tB being adapted to modify the size of the precipitates y' in at least the first or second part (2, 3) of the blade (1).

2. The method according to claim 1, characterized in that the first time tA and the second time tB are identical, the first temperature TA being different from the second temperature TB.

3. Method according to claim 1, characterized in that the first time tA and the second time tB are different, the first temperature TA being equal to the second temperature TB.

4. Method according to claim 1, characterized in that the first time tA and the second time tB are different, the first temperature TA being different from the second temperature TB.

5. A method according to any one of claims 1 to 4, characterized in that superheating is applied to the first part (2) and / or to the second part (3) of the blade (1) at a temperature T' between the solvus temperature and the burning temperature of the alloy of the blade (1).

6. A method according to any one of claims 1 to 5, characterized in that the first and second parts (2, 3) comprise, prior to the application of the first and second heat treatments, precipitates y' having the same average size, the first and second temperatures TA, TB and the first and second times t A, tB being adapted to obtain precipitates y' of different average sizes in the first and second parts (2, 3).

7. A method according to any one of claims 1 to 5, characterized in that the first and second parts (2, 3) comprise, before the application of the first and second heat treatments, precipitates y' of different average sizes, the first and second temperatures TA, TB and the first and second times ta, tB being adapted to obtain precipitates y' of identical average size in the first and second parts (2, 3).

8. A method according to any one of claims 1 to 7, characterized in that the first temperature TA is between 1170 °C and 1300 °C, the second temperature TB being between 890 °C and 1170 °C.

9. A method according to any one of claims 1 to 8, characterized in that it comprises: • a step of positioning the first part (2) of the metallic blade (1) in a first chamber (10) of a furnace configured to maintain the first part (2) at the first temperature TA, and • a step of positioning the second part (3) of the metallic blade (1) in a second chamber (12) of the furnace configured to maintain the second part (3) at the second temperature TB.

10. Single-material metallic turbine blade (1) of a turbomachine, characterized in that it is obtained by the heat treatment process as defined according to any one of claims 1 to 9.

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