CONTOUR-FOLLOWING PROTECTIVE LAYER FOR COMPRESSOR COMPONENTS OF GAS TURBINES

Abstract

Provided is a coating system for a substrate, the system including a first, second and third layer. In the system, the first layer is designed as an adhesion promoter layer, the second layer is a ductile metal layer with a columnar structure and the uppermost, third layer is a ceramic oxide layer with a high hardness value. The substrate is ideally an element of a compressor component of a stationary gas turbine. Also disclosed is a method for producing the coating system.

Claims

1. A coating system for a corrosively loaded substrate having a surface, said coating system at least comprising a first layer, a second layer and a third layer, in which the first layer, which is arranged between the surface of the substrate and the second layer, is designed as an adhesion promoter layer, the second layer is a ductile metallic layer having a columnar structure, and the third layer, which is arranged on that side of the second layer which faces away from the substrate, is a ceramic oxide layer having a hardness of at least 20 GPa.

2. The coating system as claimed in claim 1, in which the first layer comprises chromium or chromium nitride.

3. The coating system as claimed in claim 1, in which the columnar structure of the second layer consists of an aluminum-containing alloy.

4. The coating system as claimed in claim 1, in which the third layer comprises aluminum oxide and/or chromium oxide and/or an aluminum/chromium oxide in a solid solution structure.

5. The coating system as claimed in claim 1, in which the hardness of the third layer is approximately 25 GPa.

6. The coating system as claimed in claim 1, in which the substrate is a constituent part of a compressor component of a gas turbine.

7. The coating system as claimed in claim 6, in which the substrate is a constituent part of a compressor component of a stationary gas turbine.

8. A compressor component of a gas turbine having a coating system as claimed in claim 1.

9. A method for producing a coating system for a corrosively loaded substrate, comprising three layers as claimed in claim 1, wherein the material of all of the layers is applied by physical vapor deposition.

10. The method as claimed in claim 9, wherein the material of the layers is applied by cathodic arc evaporation and/or by sputtering.

Description

BRIEF DESCRIPTION

[0017] Some of the embodiments will be described in detail, with references to the following figures, wherein like designations denote like members, wherein:

[0018] FIG. 1 shows an embodiment of a coating system;

[0019] FIG. 2 shows an electron microscopy image of the embodiment as shown in FIG. 1; and

[0020] FIG. 3 shows a flowchart of an embodiment of the method according to embodiments of the invention.

DETAILED DESCRIPTION

[0021] In the embodiment shown in FIG. 1, the coating system 1 has a substrate 2 having a surface 2a, a first layer 3, a second layer 4 and a third layer 5. The substrate 2 comprises at least one metal and may be a metal alloy. Under corrosive conditions, the substrate 2 may be susceptible to corrosion.

[0022] The first layer 3 is arranged on the surface 2a and has a thickness of approximately 100 nm. It preferably consists of chromium or chromium nitride, but in its property as an adhesion promoter layer it can also comprise other metals or have a different composition, e.g. of the type MCrAlY.

[0023] The second layer 4 is arranged on the first layer 3 and has a thickness in the range of 0.5-5.0 ?m, preferably of 1.0-3.0 ?m. The second layer 4 is a ductile metallic layer having a columnar structure consisting of an aluminum alloy. By way of example, the second layer 4 consists of an alloy comprising aluminum and chromium; alternatively, however, the alloy can also contain further metals or metals other than chromium.

[0024] The third layer 5 is arranged on the second layer 4 and has a thickness in the range of 0.5-10.0 ?m, preferably of 1.0-5.0 ?m. The third layer 5 is a hard ceramic oxide layer having a very dense structure. The material of the third layer 5 is a mixture of chromium oxide and aluminum oxide, preferably of a solid solution compound of aluminum/chromium oxide and additional Al-Cr intermetallic compounds. Further oxides and other compounds or elements can also be present in the third layer 5. The third layer 5 is resistant to corrosion since it already consists of oxides. As a result, the third layer 5 protects the substrate 2 and the other layers against corrosion. The ceramic constituents give the third layer 5 a high hardness, which is typically up to 25 GPa. The third layer 5 is therefore considerably harder than the substrate 2 and the other layers. The high hardness becomes effective against erosion, particularly against drop impingement erosion and particle erosion.

[0025] The thickness of the coating system in total may be up to 20 ?m. In this case, the individual layers, particularly the second layer 4 and the third layer 5, may also have a higher thickness than that indicated above. The embedding compound 6 shown in FIG. 2 is applied to the third layer 5 for metallographic investigations. The embedding layer comprises inorganic oxides. FIG. 2 is a representation of a scanning electron microscopy image of a coating system 1, in which the first layer 3 is barely visible owing to its small thickness.

[0026] The substrate 2 preferably belongs to a compressor component, preferably to a compressor blade of a stationary gas turbine. However, it may also belong to another component of a stationary gas turbine or of another gas turbine.

[0027] For producing the coating system 1 described, in one embodiment of the method as per the illustration of FIG. 3, a substrate 2 having a surface 2a is provided in a first step S1. In a second step S2, the material of the first layer 3 is applied by physical vapor deposition (PVD). In a third step S3, the material of the second layer 4 is applied likewise by PVD. In a fourth step S4, the material of the third layer 5 is applied likewise by PVD.

[0028] In this case, cathodic arc evaporation is carried out as the preferred method of the PVD. A method which is likewise preferred is sputtering. It is likewise preferable if the two methods are combined with one another. Further possible usable methods, which can be used alternatively and/or in combination with the aforementioned methods, are thermal evaporation, electron beam evaporation, laser beam evaporation or arc evaporation.

[0029] Although the invention has been illustrated and described in greater detail with reference to the preferred exemplary embodiment, the invention is not limited to the examples disclosed, and further variations can be inferred by a person skilled in the art, without departing from the scope of protection of the invention.

[0030] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.