VANE SEGMENT FOR A GAS TURBINE

Abstract

A vane device for a gas turbine having an inner shroud and an outer shroud, an aerofoil arranged between the inner shroud and the outer shroud, the aerofoil and/or inner shroud and/or an outer shroud having a first layer of MCrAlY coating over a substrate, a coated surface section which is coated with a thermal barrier coating over the first layer of MCrAlY coating, a second layer of MCrAlY coating provided between the first layer of MCrAlY and the thermal barrier coating of the coated surface section.

Claims

1. A vane device for a gas turbine, the vane device comprising: an inner shroud and an outer shroud, at least an aerofoil arranged between the inner shroud and the outer shroud, the aerofoil and/or inner shroud and/or an outer shroud comprising a first layer of MCrAlY coating over a substrate for providing thermal protection to the substrate, at least a coated surface section which is coated with a thermal barrier coating over the first layer of MCrAlY coating for providing additional protection at high temperature, wherein a second layer of MCrAlY coating is provided between the first layer of MCrAlY and the thermal barrier coating of the coated surface section.

2. The vane device according to claim 1, wherein the first layer of MCrAlY coating is obtained by means of an electroplating process.

3. The vane device according to claim 1, wherein the second layer of MCrAlY coating is obtained by means of an air plasma spray process.

4. The vane device according to claim 1, wherein the second layer of MCrAlY coating has a roughness greater than the roughness of the first layer of MCrAlY coating.

5. The vane device according to claim 1, wherein the first layer of MCrAlY coating covers the entire substrate of the aerofoil and/or inner shroud and/or an outer shroud along a gas path of a working fluid of the gas turbine.

6. The vane device according to claim 1, wherein the material of the substrate is Mar-M-247.

7. The vane device according to claim 1, wherein the aerofoil comprises a suction side and a pressure side, the suction side comprising at least a first coated surface section which is coated with a thermal barrier coating.

8. The vane device according to claim 1, wherein the inner shroud and the outer shroud respectively comprise a first inner platform and a second inner platform, the first inner platform and/or the second inner platform comprising a coated surface section coated with a thermal barrier coating.

9. The vane device according to claim 8, wherein the coated surface section is located downstream of a trailing edge of the aerofoil.

10. The vane device according to claim 1, wherein the pressure side of the aerofoil is free from thermal barrier coating.

11. A method for manufacturing a vane device for a gas turbine, wherein the vane device comprises an inner shroud and an outer shroud, at least an aerofoil arranged between the inner shroud and the outer shroud, the inner shroud, the outer shroud and the aerofoil defining a gas path for a working fluid of the gas turbine, the method comprising: coating a substrate of the airfoil and/or inner shroud and/or an outer shroud with a first layer of MCrAlY coating for providing thermal protection to the substrate, coating a second layer of MCrAlY coating over a portion of the first layer of MCrAlY coating, coating a thermal barrier coating over the second layer of MCrAlY coating for providing a coated surface section having additional protection at high temperature.

12. The method according to claim 11, wherein the first layer of MCrAlY coating is applied by an electro-plating (EP) process and the second layer of MCrAlY coating is applied by an Air Plasma Spray (APS) process.

13. The method according to claim 11, wherein the first layer of MCrAlY coating is smoothed by means of a vibro-polishing process.

14. The method according to claim 11, wherein the thermal barrier coating is applied by an Electron Beam Physical Vapour Deposition or an Air Plasma Spray (APS) process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

[0020] FIG. 1 shows a schematic view of a vane segment comprising two aerofoils according to an exemplary embodiment of the present invention;

[0021] FIG. 2 shows an enlarged sectional view of a coated surface section of an aerofoil as shown in FIG. 1 according to an exemplary embodiment of the present invention.

[0022] FIG. 3 shows a schematic view of an aerofoil comprising a coated surface section according to an exemplary embodiment of the present invention;

[0023] FIG. 4 shows a schematic view of an inner platform of a vane segment comprising a further coated surface section according to an exemplary embodiment of the present invention; and

[0024] FIG. 5 shows a perspective view of a vane device according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0025] The illustrations in the drawings are schematic. It is noted that in different figures, similar or identical elements are provided with the same reference signs.

[0026] FIG. 1 shows a vane device (segment) 100 for a gas turbine. The vane device 100 comprises a first aerofoil 101 comprising a first suction side 107 and a first pressure side 108, a second aerofoil 115 comprising a second suction side 118 and a second pressure side 119, an inner shroud 110 and an outer shroud 120. The first aerofoil 101 and the second aerofoil 115 are arranged between the inner shroud 110 and the outer shroud 120 and are spaced apart from each other along a circumferential direction with respect to a rotary axis of the gas turbine.

[0027] According to other embodiments of the present invention, a vane device (segment) 100 for a gas turbine comprises more aerofoils than the two aerofoils 101, 115 shown in FIG. 1.

[0028] The inner shroud 110 comprises an inner platform 111 and the outer shroud 120 comprises a further inner platform 121. According to the view shown in FIG. 1, the shown inner platform 111, 121 may be the respective inner platform 111, 121 of the inner shroud 110 or of the outer shroud 120. The first aerofoil 110 and the second aerofoil 115 are attached to the inner platforms 111, 121, i.e. the suction sides 107, 118 and the pressure sides 108, 119 extend from on to the other of the inner platforms 111, 121.

[0029] The suction sides 107, 118, the pressure sides 108, 119 and the inner platforms 111, 121 delimit, in the vane device 100 a gas path which is washed during operation of the gas turbine by a working fluid of the gas turbine.

[0030] The flow direction F of the working fluid in the gas turbine is indicated by the arrow shown in FIG. 1. The working fluid flows along the gas path of the vane device 100, from the respective leading edges 102, 116 of the respective aerofoils 101, 115 up to the respective trailing edges 103, 117 of the respective aerofoils 101, 115. At the trailing edges 103, 117 the working fluid flows away from the aerofoils 101, 115.

[0031] Along the gas path, the first aerofoil 101, the second aerofoil 115 and the inner platforms 111, 121 are coated with a first layer 202 of MCrAlY coating (shown in FIG. 2). The first layer 202 is obtained by electroplating (EP) and provides a smooth surface along the gas path of the vane device 100. The first layer 202 provides an improved resistance to oxidation.

[0032] A further smoothing is achieved, according to a possible embodiment of the present invention, by applying a vibro-polishing process to the first layer 202 of MCrAlY after the electroplating process.

[0033] The MCrAlY composition comprises indicated by the M in particular Nickel (Ni), Cobalt (Co) or a mixture of both.

[0034] Along the gas path, at least the first suction side 107 comprises a coated surface section 104 which is coated with a thermal barrier coating (TBC) and which represents at least a part of the total surface of the first suction side 107. The thermal barrier coating 104 comprises a ceramic component. The coated surface section 104 provides, with respect to the first layer 202 of MCrAlY coating, additional protection at high temperature. It has been measured that the hottest sections of the surface of the respective aerofoils 101, 115 are in particular at the suction side 107, 118 of the respective aerofoils 101, 115. Hence, as shown in FIG. 1, the coated surface section 104 is coated onto the first suction side 107 of the first aerofoil 101 in order to increase the heat resistance. Furthermore, a respective coated surface section 104 may also be applied to a second suction side 118 of the second aerofoil 115.

[0035] The inner platform 111 and/or the further inner platform 121 comprise(s) the further coated surface section 106 in the exemplary embodiment as shown in FIG. 1.

[0036] In fact, it has been additionally found out that in a region along the inner platform 111, 121 downstream of the trailing edges 103, 117 of the aerofoils 101, 115 the hottest spots caused by the working fluid exist. Hence, by the present invention, at the downstream section of the respective inner platforms 111, 121 between the respective trailing edges 103, 117 and respective trailing edges 112, 122 of the respective inner platforms 111, 121 a further coated surface section 106 is applied.

[0037] The further coated surface section 106 is optional, and according to other embodiments of the present invention, may not be present.

[0038] According to other embodiments of the present invention, only the coated surface section 106 on the inner platform 111 and/or the further inner platform 121 is present, while the aerofoils 101, 115 are free from the coated surface section 104.

[0039] FIG. 2 shows a more detailed view of the coated surface section 104 at the first aerofoil 101 as shown in FIG. 1.

[0040] To a substrate 203 of the first aerofoil 101, the first layer 202 of MCrAlY coating is applied for improving the oxidation resistance. The material of the substrate 203 is a Mar-M-247 alloy.

[0041] According to other embodiments of the present invention, the material of the substrate 203 is another alloy.

[0042] On top of the first layer 202 of MCrAlY coating, the thermal barrier coating of the coated surface section 104 is applied. Between the first layer 202 of MCrAlY coating and the coated surface section 104, a second layer 302 of MCrAlY coating is provided.

[0043] The second layer 302 of MCrAlY coating is obtained by means of an Air Plasma Spray (APS) process and provides a rough surface, which is optimal for the bonding of the coated surface section 104.

[0044] As shown in FIG. 2, the coated surface section 104 comprises a thinning out section 201. Within the thinning out section 201, the thickness of the thermal barrier layer in the coated surface section 104 is reduced till zero thickness at an end edge of the coated surface section 104.

[0045] FIG. 3 shows more in detail the positioning of the coated surface section 104 on the first aerofoil 101.

[0046] As shown in FIG. 3, the thermal barrier layer of the coated surface section 104 is located at the suction side 108 of the first aerofoil 101. At the edge of the coated surface section 104 which is closer to the leading edge 102, a thinning out section 201 of the thermal barrier layer is applied in order to smoothly reduce the thickness of the thermal barrier layer till zero thickness.

[0047] Specifically, the coated surface section 104 is coated to the first aerofoil 101, over the second layer 302 of MCrAlY coating, between a maximum aerofoil thickness (measured e.g. along a line perpendicular to a chord line of a respective aerofoil 101, 115) of the aerofoil 101 and the trailing edge 103 of the first aerofoil 101. The section between the edge of the coated surface section 104 and the leading edge 102 is kept free from any thermal barrier layer.

[0048] Furthermore, as shown in FIG. 3, the pressure side 109 may be kept free from a thermal barrier coating. Furthermore, at an upstream section of the respective inner platforms 111, 121 between the respective leading edges 102, 116 and respective upstream leading edges 112, 122 of the respective inner platforms 111, 121 the surfaces may be kept free from a thermal barrier coating. Hence, only at the hottest region of the aerofoil 101, the thermal barrier coating is applied in order to effectively apply the thermal barrier coating and hence to reduce weight and costs.

[0049] FIG. 4 shows an enlarged view of the inner shroud 110. The outer shroud 120 may be formed in a similar design.

[0050] Between a trailing edge 103 of the first aerofoil 101 and the trailing edge 112 of the inner platform 111 of the inner shroud 110, the further coated surface section 106 comprising the TBC coating is applied. At the respective upstream and downstream edges of the further coated surface section 106, a respective thinning out section 201, 201 is formed at which the thermal barrier coating is reduced till zero thickness. As shown in FIG. 4, a first layer 202 of MCrAlY coating is applied to the substrate 203. The first layer 202 of MCrAlY is applied along the inner surface of the inner platform 111 and around the trailing edge 112 of the inner platform 111. The further coated surface section 106 is applied over the second layer 302 of APS MCrAlY coating.

[0051] The further coated surface section 106 and the second layer 302 of APS MCrAlY coating are only applied at the inner surface of the inner platform 111 where the working fluid washes and contacts the surface of the inner platform 111.

[0052] FIG. 5 shows a perspective view of the vane device 100, wherein the vane device 100 comprises the inner shroud 110, the outer shroud 120, the first aerofoil 101 and the second aerofoil 115. The vane device 100 as shown in FIG. 5 may have the same features as shown in the sectional view shown in FIG. 1. Additionally, FIG. 5 shows the coated surface section 104, wherein the coated surface section 104 is spaced from the first leading edge 102 of the first aerofoil 101, as shown for example in FIG. 3. Furthermore, the coated surface section 104 is spaced apart by a distance x from the inner platform 111 and the further inner platform 121, for example.

[0053] In particular, the sections between the inner platform and the edges of the coated surface section 104 (i.e. so-called fillet sections) are free from the thermal barrier coating and only coated by the first layer 202 of electroplated MCrAlY, for example.

[0054] It should be noted that the term comprising does not exclude other elements or steps and a or an does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.