Joint between a metal part and a ceramic part based SiC and/or C

1. An assembly between a metal piece and a ceramic material piece made of a SiC and/or C based ceramic material, the assembly comprising:

a stack structure comprising the following elements assembled together in pairs in this order, by brazing:

said metal piece;

a first intermediate piece;

a second intermediate piece that is made of AlN or of mullite, and that presents a coefficient of expansion smaller than that of the material constituting said metal piece; and

said ceramic material piece,

wherein the first intermediate piece is made of metal and is suitable for deforming to compensate for expansion difference between the metal piece and the second intermediate piece.

2. An assembly according to claim 1 , wherein the second intermediate piece presents rigidity and/or breaking strength greater than that of the ceramic material piece.

3. An assembly according to claim 1 , wherein the ceramic material piece is made of solid SiC.

4. An assembly according to claim 1 , wherein the ceramic material piece is made of ceramic matrix composite material.

5. An assembly according to claim 4 , wherein the composite material comprises a matrix based on SiC and/or C, reinforced by fibers of SiC and/or C.

6. An assembly according to claim 1 , wherein the metal piece is made of an alloy based on Ni or based on Co.

7. An assembly according to claim 1 , wherein the first intermediate piece is made of Ni or of an alloy based on Ni, or of Co, or of an alloy based on Co.

8. An assembly according to claim 1 , wherein a first brazing composition is used for assembling the first intermediate piece to the metal piece, and/or to the second intermediate piece, the first composition being based on Ni and including an atomic percentage of Ti less than or approximately 10%, with the first composition including the following elements: Fe, Cr, and Si.

9. An assembly according to claim 8 , wherein the first brazing composition comprises, in atomic percentages: 3% to 6% Ti when the second intermediate piece is made of AlN; and 6% to 10% Ti when the second intermediate piece is made of mullite.

10. An assembly according to claim 1 , wherein a first brazing composition is used for assembling the first intermediate piece to the metal piece and/or to the second intermediate piece, the first composition being based on Pd and Ni.

11. An assembly according to claim 1 , wherein a second brazing composition is used for assembling the second intermediate piece made of A 1 N or of mullite to the ceramic material piece based on SiC and/or C, the second composition being based on Si.

12. An assembly according to claim 11 , wherein the second brazing composition essentially comprises, in atomic percentages: 60% to 97% Si, and 40% to 3% Zr, and includes an eutectic mixture of ZrSi 2 and of Si.

13. An assembly according to claim 11 , wherein the second brazing composition essentially comprises, in atomic percentages: 78% to 97% Si;

and 22% to 3% Pr; and includes an eutectic mixture of PrSi 2 and of Si.

14. An assembly according to claim 1 , wherein the first intermediate piece comprises a layer of ductile metal material.

15. An assembly according to claim 1 , wherein the first intermediate piece comprises a deformable structure.

16. An assembly according to claim 15 , wherein the deformable structure includes a deformable sheet presenting deformable zones, in a form of concentric undulations, together with flat zones that are brazed.

17. A method of making an assembly according to claim 1 , comprising:

brazing together the ceramic piece and the second intermediate piece with help of a second brazing composition; and

brazing together the second intermediate piece, the first intermediate piece, and the metal piece are with help of a first brazing composition having a melting temperature lower than that of the second brazing composition.

18. A method of making an assembly according to claim 1 , wherein the ceramic piece, the second intermediate piece, the first intermediate piece, and the metal piece are brazed together in a single operation.

19. A turbomachine comprising at least one assembly according to claim 1 .

20. A turbomachine according to claim 19 , further comprising a nozzle including the at least one assembly, in which the metal piece is a casing or a lever of the nozzle, and the ceramic material piece is a flap of the nozzle.

21. A turbomachine according to claim 19 , further comprising a combustion chamber including the at least one assembly, in which the metal piece is a casing, a gasket, or a component part of the combustion chamber, and the ceramic material piece is another component part of the combustion chamber.

22. A turbomachine according to claim 19 , further comprising a post-combustion equipment including the at least one assembly, in which the metal piece is a post-combustion casing or a platform, and the ceramic material piece is a flame-holder arm.

23. A brazing composition for assembling two pieces together by brazing, one of the pieces being made of a ceramic based on SiC and/or on C, and the other piece being made of a ceramic based on SiC, on C, on AlN, or on mullite, the composition being essentially constituted by a mixture of PrSi 2 and of Si, in which Si is in the majority and Pr in the minority, in atomic percentages.

24. A brazing composition according to claim 23 , wherein the mixture of PrSi 2 and of Si comprises, in atomic percentages: 78% to 97% Si; and 22% to 3% Pr; and includes an eutectic mixture of PrSi 2 and of Si.