Turbomachine blade with erosion and corrosion protective coating and method of manufacturing

1. A turbomachine blade comprising:

a blade body; and

a corrosion protective multilayered coating bonded to the blade body, the multilayered coating comprising an erosion and corrosion resistant first layer at least covering a corrosion and erosion critical area of the blade body and a sacrificial second layer covering the first layer;

wherein the second layer comprises a sacrificial slurry coating; and

wherein the sacrificial slurry coating is formed of a closely packed aluminum-filled chromate/phosphate basecoat sealed with a chemically inert chromate/phosphate topcoat.

2. A turbomachine blade according to claim 1 , wherein the first layer exclusively covers the corrosion and erosion critical area of the blade body.

3. A turbomachine blade according to claim 1 , wherein the second layer completely covers the blade body.

4. A turbomachine blade according to claim 1 , wherein the first layer is sandwiched between the blade body and the second layer.

5. A turbomachine blade according to claim 1 , wherein the corrosion critical area is a leading edge area of the blade.

6. A turbomachine blade according to claim 5 , wherein the first layer covers an area of up to 30% of the chord length, starting from the leading edge towards the trailing edge, of the blade body.

7. A turbomachine blade according to claim 5 , wherein the first layer covers an area of from 5% to 30% of the chord length, starting from the leading edge towards the trailing edge, of the blade body.

8. A turbomachine blade according to claim 5 , wherein the first layer covers an area of up to 60% of the chord length, starting from the leading edge towards the trailing edge, of the blade body.

9. A turbomachine blade according to claim 1 , wherein the first layer has a layer thickness in the range of from 50 to 100 micrometers.

10. A turbomachine blade according to claim 1 , wherein the second layer has a layer thickness in the range of from 50 to 100 micrometers.

11. A turbomachine blade according to claim 1 , wherein the first layer is formed of a material selected to provide erosion resistance against the impact of water droplets or particles.

12. A turbomachine blade according to claim 1 , wherein the blade body material is stainless steel.

13. A turbomachine blade according to claim 12 , wherein the first layer is formed of a material selected to provide stainless steel corrosion resistance.

14. A turbomachine blade according to claim 1 , wherein a roughness of the first layer is less than 2.3 micrometer.

15. A turbomachine blade according to claim 1 , wherein the first layer is a braze tape or foil containing a matrix of braze alloy with an erosion resistant filler of abrasive particles.

16. A turbomachine blade according to claim 15 , wherein the braze alloy is a Silver (Ag)-based alloy or an Aluminum (Al)-based alloy.

17. A turbomachine blade according to claim 15 , wherein the erosion resistant filler is a filler material selected from the group consisting of Al 2 O 3 , WC, and CrC, and combinations thereof.

18. A turbomachine blade according to claim 15 , wherein the filler content ranges from 60 Vol.-% to 90 Vol.-% of the first layer.

19. A turbomachine blade according to claim 15 , wherein sizes of the filler particles range from 10 to 30 micrometers.

20. A turbomachine blade according to claim 1 , wherein the first layer material has been deposited by a technique selected from the group consisting of HVOF (High Velocity Oxygen Fuel)-spraying, tape/foil brazing, CVD (Chemical Vapor Deposition), laser cladding, and combinations thereof.

21. A turbomachine blade according to claim 1 , wherein the first layer has been deposited by HVOF (High Velocity Oxygen Fuel)-spraying technique, and the first layer is formed of a material selected from the group consisting of stainless steel, nickel (Ni)-based alloys, and combinations thereof.

22. A turbomachine blade according to claim 1 , wherein a roughness of the sacrificial slurry coating is less than 1.6 micrometers.

23. A turbomachine blade according to claim 1 , wherein the blade is a compressor blade.

24. A method of manufacturing a turbomachine blade, the method comprising:

providing a blade body;

depositing an erosion and corrosion resistant first layer on the blade body to cover at least a corrosion critical area of the blade body; and

after said depositing the first layer, depositing a sacrificial slurry coating over the first layer to cover at least the first layer, wherein the sacrificial slurry coating is formed of a closely packed aluminum-filled chromate/phosphate basecoat sealed with a chemically inert chromate/phosphate topcoat.

25. A method according to claim 24 , wherein depositing the first layer comprises depositing to exclusively cover the corrosion critical area of the blade body.

26. A method according to claim 24 , wherein depositing the second layer comprises depositing to completely cover the blade body.

27. A method according to claim 24 , wherein depositing the first layer comprises depositing using a deposition technique selected from the group consisting of HVOF (High Velocity Oxygen Fuel)-spraying, tape/foil brazing, CVD (Chemical Vapor Deposition), laser cladding, and combinations thereof.

28. A method according to claim 24 , wherein depositing the first layer comprises depositing using HVOF (High Velocity Oxygen Fuel)-spraying, and wherein the first layer is formed of a material selected from the group consisting of stainless steel, nickel (Ni)-based alloy, and combinations thereof.

29. A method according to claim 24 , wherein depositing a first layer comprises depositing a first layer to cover at least a leading edge area of the blade body.