DETAILED DESCRIPTION OF THE INVENTION

FIG. 4 schematically illustrates a thermal barrier section 10 covering the substrate 2 with a turbine part 1.

The elements illustrated in FIG. 4 can be independently representative of the elements of a turbine blade 6, of a distributor fin, or of any other element, part or part of a turbine.

The substrate 2 is formed from a nickel-based superalloy comprising rhenium and / or ruthenium. The average mass fraction of rhenium and / or ruthenium substrate 2 is greater than or equal to 0.04 and preferably between 0.045 and 0.055.

The thermal barrier comprises a metallic sub-layer 3b, a protective layer 4 and a thermally insulating layer 9.

The substrate 2 is covered by the metallic sublayer 3b. The metal layer 3b is covered by the protective layer 4. The protective layer 4 is covered by the thermally insulating layer 9.

The composition of the metallic sub-layer 3b deposited has an average atomic fraction of aluminum between 0.15 and 0.25, preferably between 0.19 and 0.23, in chromium between 0.03 and 0.08, preferably between 0.03 and 0.06, platinum between 0.01 and 0.05, hafnium less than 0.01, preferably less than 0.008, and silicon less than 0.01, preferably less than 0.008. The preferred composition is described in Table 1 below, the average atomic fraction being given as a percentage.

Ni (¾ At) Al (¾ At) Cr (¾ At) Pt (¾ At) Hf (¾ At) Si (¾ At) base 19-23 3-6 1 -5 0-0.8 0-0.8

Table 1

The metallic sublayer 3b has a majority γ'-ΝΪ3ΑΙ 12 phase by volume. Thus, the allotropic structure of the sublayer 3b is close to the structure of the substrate 2, making it possible to prevent the formation of secondary reaction zones during the use of the turbine part 1 at temperatures above 900 ° C, and preferably greater than 1,100 ° C. Advantageously, the Y'-Ni 3 Al phase is greater than 95% by volume in the metal sublayer. Apart from the γ'-Νι ' 3 ΑΙ phase, the metallic sublayer 3b may have a β-NiAlPt phase or a γ-Ni phase.

The chemical composition and allotropic structure of sublayer 3b were determined by analyzing the chemical composition and structure of a sublayer 3b, initially of the β-NiAlPt type, directly after a martensitic transformation phase during a treatment of the sub-layer 3b simulating the thermal conditions of use of part 1.

FIG. 5 is a photomicrograph of the section of an underlayer 3a, different from an underlayer of the invention, covering a substrate after a heat treatment. The substrate covered by the sublayer 3a is a substrate in nickel-based superalloy of AM1 type, comprising neither rhenium nor ruthenium. The part comprising the sub-layer 3a was treated by a series of 250 thermal cycles, each cycle corresponding to a heat treatment of the part comprising the sub-layer 3a at a temperature of 1100 ° C. for 60 min. The sub-layer 3a presents mainly in volume a phase 1 1 β-NiAlPt and in a minority in volume a phase 12 γ'-Νι ' 3ΑΙ. The sub-layer 3a is covered with a protective layer 4. The interface between the sub-layer 3a and the protective layer 4 is very irregular: it has a sufficiently high roughness to cause chipping (or rumpling) of the layer. protective cover 4 when using the part. This roughness is caused during the heat treatment by martensitic transformations of the 1 1 6-NiAlPt phases in the sublayer 3a.

FIG. 6 is a photomicrograph of the section of an underlayer 3b, in accordance with one embodiment of the invention, covering a substrate 2 in monocrystalline nickel-based superalloy comprising rhenium and / or ruthenium, after a heat treatment . The part comprising the sub-layer 3b was treated by a series of 500 thermal cycles, each cycle corresponding to a heat treatment of the part 1 comprising the sub-layer 3b at a temperature of 1100 ° C. for 60 min. The sub-layer 3b mainly has in volume a phase 12 Y'-Ni 3Al and a minority by volume a phase 1 1 6-NiAlPt. The sub-layer 3a is covered with a protective layer 4. The interface between the sub-layer 3b and the protective layer 4 has a lower roughness than the roughness between the sub-layer 3a and the protective layer 4 illustrated on the figure. Figure 5, despite a heat treatment of the system comprising the sub-layer 3b longer than the heat treatment described with reference to Figure 5. This difference in roughness is associated with a martensitic transformation of the phases 1 1 β-NiAlPt of the sub- layer 3b faster than that of phases 1 1 β-NiAlPt of sublayer 3a. In addition, the sublayer 3b illustrated in FIG. 6 mainly has in volume a phase 12 γ'-Νι '

The allotropic structure and the chemical composition of the sub-layer 3b, after 500 thermal cycles were analyzed and selected. This structure and this composition correspond to the structure and to the compositions described above, in particular in Table 1.

Thus, by a phase 12 γ'-Νι ' 3 ΑΙ predominant in volume and by the composition described in Table 1, the sublayer 3b is little or not subject to martensitic transformations causing the phenomenon of

rumpling, while exhibiting a composition making it possible to increase the time, in working condition, during which the protective sub-layer 4 can be formed.

The sublayer 3b can be deposited under vacuum, for example by vapor phase (PVD process, acronym of the English term Physical Vapor Déposition). Different PVD methods can be used for the fabrication of the sublayer 3b, such as sputtering, joule evaporation, laser ablation and electron beam assisted physical vapor deposition. The sub-layer 3b can also be deposited by thermal spraying.

Thus, the sublayer 3b can be deposited on the substrate 2 by having, before any heat treatment, a chemical composition and an allotropic structure suitable for avoiding the phenomenon of rumpling.

These deposition methods also allow a simplification of the formation of the sublayer 3b on the substrate 2 as well as better control of the chemical composition of the sublayer 3b.

Finally, these deposition methods make it possible to precisely control the thickness of the sublayer 3b, unlike the methods of forming a metallic sublayer by diffusion of a chemical element. Advantageously, the thickness of the sublayer 3b is between 5 μητι and 50 μιτι.

Several targets of different metallic materials can be used in parallel, simultaneously, during the deposition of an underlayer 3b. This type of deposition can be carried out by co-evaporation or by co-sputtering: the speed, respectively of evaporation, or of sputtering imposed on each target during the deposition of the sublayer 3b then determines the stoichiometry of said layer.
CLAIMS

1. Turbine part (1) comprising a substrate (2) in monocrystalline nickel-based superalloy, comprising rhenium and / or ruthenium, and having a majority γ'-ΝΪ3ΑΙ phase by volume and a γ-Ni phase, and an underlayer (3b) in a nickel-based metal superalloy covering the substrate (2), characterized in that the sub-layer (3b) has a majority γ'-ΝΪ3ΑΙ phase (12) by volume and in that the sub-layer (3b) has an average atomic fraction:

- aluminum between 0.15 and 0.25;

- in chromium between 0.03 and 0.08;

- in platinum between 0.01 and 0.05;

- in hafnium less than 0.01 and

- silicon less than 0.01.

2. Part according to claim 1, wherein the sublayer (3b) has a γ '- Ni 3 Al phase (12) greater than 95% by volume.

3. Part according to claim 1 or 2, wherein the sublayer (3b) has a γ'-Νι ' 3 ΑΙ phase (12) and a 6-NiAlPt phase (1 1).

4. Part according to claim 1 or 2, wherein the sublayer (3b) has a γ'-Νι ' 3 ΑΙ phase (12) and a γ-Νι ' phase .

5. Part according to one of claims 1 to 4, wherein the mass fraction of rhenium of the substrate (2) is greater than or equal to 0.04.

6. Part according to one of claims 1 to 4, wherein the sublayer (3b) further comprises at least one element selected from cobalt, molybdenum, tungsten, titanium, tantalum.

7. Part according to one of claims 1 to 6, comprising a protective layer (4) of aluminum oxide covering the sublayer (3b).

8. Part according to claim 7, comprising a thermally insulating layer (9) of ceramic covering the protective layer (4).

9. Part according to one of claims 1 to 8, wherein the thickness of the sublayer (3) is between 5 μητι and 50 μητι.

10. Turbine blade (6) characterized in that it comprises a part (1) according to one of claims 1 to 9.

1 1. Turbomachine characterized in that it comprises a turbine comprising a turbine blade (6) according to claim 10.

1 2. A method of manufacturing a turbine part (1) comprising a vacuum deposition step of an underlayer (3b) of a nickel-based superalloy having predominantly by volume a Y'-Ni 3 Al phase , on a substrate (2) in a nickel-based superalloy comprising rhenium and / or ruthenium, the sub-layer (3b) having an average atomic fraction:

- aluminum between 0.15 and 0.25;

- in chromium between 0.03 and 0.08;

- in platinum between 0.01 and 0.05;

- in hafnium less than 0.01 and

- silicon less than 0.01.

1 3. The method of claim 12, wherein the deposition is implemented by a method chosen from a physical vapor deposition, thermal spraying, Joule evaporation, pulsed laser ablation and sputtering.

14. The method of claim 12 or 13, wherein the sublayer (3b) is deposited by co-spraying and / or co-evaporating metal targets.