Method of manufacturing or repairing a coating on a metallic substrate

1. A method of repairing a coating forming a thermal barrier on a superalloy substrate, wherein said coating to be repaired is a ClA coating obtained by prior deposition of chromium onto the superalloy substrate followed by a step of vapor aluminizing onto the chromium, and wherein the following steps are carried out in a zone or zones of the coating to be repaired:

a) completely removing a spoilt coating down to the superalloy substrate;

b) forming a pre-layer on the superalloy substrate by applying one or more layers of a paint containing at least one metal selected from the group consisting of platinum class metals (platinoids) and chromium; and

c) vapor aluminizing onto the pre-layer, to obtain an aluminide of said at least one metal.

2. A method according to claim 1 , wherein said metal is platinum.

3. A method according to claim 1 , wherein said pre-layer is formed with a thickness within a range of 1 μm to 30 μm.

4. A method according to claim 3 , wherein said thickness is within a range of 2 μm to 10 μm.

5. A method according to claim 1 , wherein said pre-layer is formed by applying said paint using a brush, a spray gun, a pad, and/or by immersion (dip-coating).

6. A method according to claim 1 , wherein said steps are performed only on said zone or zones to be replaced and not on other zones which are in good condition.

7. A method according to claim 1 , wherein forming said pre-layer is performed by applying a plurality of layers of said paint.

8. A method according to claim 1 , wherein said paint is a suspension of solid material in a liquid, said solid material being a metal powder of said at least one metal.

9. A method according to claim 8 , wherein said liquid is water-based.

10. A method according to claim 8 , wherein said liquid is oil based.

11. A method according to claim 8 , wherein said liquid is based on an hydrocarbon mixture.

12. A method according to claim 1 , wherein forming a pre-layer by applying one or more layers of paint occurs immediately before vapor aluminizing onto the pre-layer.

13. A method according to claim 1 , wherein the vapor aluminizing includes exposing the pre-layer to NH 4 F.

14. A method of manufacturing or repairing a coating forming a thermal barrier on a superalloy substrate, wherein said coating comprises a binding sub-layer formed by an MCrAlY alloy, M being a metal selected from the group consisting of nickel, cobalt, iron and a mixture of said metals, said binding sub-layer being modified by forming a pre-layer on a surface of said binding sub-layer by:

first applying one or more layers of a paint including chromium to the binding sub -layer, and

second, performing diffusion heat treatment of the one or more layers of paint.

15. A method according to claim 14 , wherein said pre-layer is formed with a thickness within a range of 1 μm to 30 μm.

16. A method according to claim 14 , wherein said pre-layer is formed by applying said paint using a brush, a spray gun, a pad, and/or by immersion (dip-coating).

17. A method according to claim 15 , wherein said thickness is within a range of 2 μm to 10 μm.

18. A method according to claim 14 , wherein said sub-layer comprises NiAl.

19. A method according to claim 14 , wherein said sub-layer is based on an aluminide.

20. A method according to claim 14 , wherein said paint is a suspension of solid material in a liquid, said solid material being a metal powder of said at least one metal.

21. A method according to claim 20 , wherein said liquid is water-based.

22. A method according to claim 20 , wherein said liquid is oil based.

23. A method according to claim 20 , wherein said liquid is based on an hydrocarbon mixture.