ROTOR BLADE, METHOD FOR MANUFACTURING ROTOR BLADE, AND GAS TURBINE ENGINE

Abstract

The present invention relates to a rotor blade (30) for a gas turbine engine (50), characterized by a coating (10) on a blade tip (20) of the rotor blade (30) including an oxidation-resistant abrasive layer (11), and the rotor blade tip (20) having at least in part an orientation plane (21) having a normal vector (22) having a component (23) in the direction of rotation of the rotor blade (R). The present invention further relates to a method of manufacturing the rotor blade (30), and to a gas turbine engine (50) having the rotor blade (30).

Description

[Technical field]

[0001] The invention relates to a rotor blade for a gas turbine engine having the features of claim 1, to a method for manufacturing a rotor blade having the features of claim 9 and to a gas turbine engine according to claim 12. [Background technology]

[0002] In gas turbine engines, the quality of the sealing systems between rotating and stationary components strongly influences the efficiency of the gas turbine engine.

[0003] It is therefore important to maintain minimum clearances between rotating and stationary components during nominal and / or transient operation. It is known to achieve this by a combination of an abradable coating on the seal segments of the turbine shroud and an abrasive coating on the rotor blade tips.

[0004] The abradable coating is typically porous and only weakly bonded, and the abrasive rotor blade tip allows the seal to form by nicking the abradable coating during the first run.

[0005] Rotor blade tip coatings are further used to protect the rotor blade tips from wear and oxidation. Known rotor blade tip coatings include abrasive particles (such as cubic boron nitride) embedded in a matrix (such as MCrAIX). "M" represents the metal, most of which are cobalt, nickel, or cobalt-nickel alloys. "Cr" represents chromium, "Al" represents aluminum, and "X" represents yttrium or hafnium.

[0006] Such coatings are applied according to the prior art by complex and cost-intensive processes such as electrolytic or electrophoretic deposition (US Pat. No. 935,407). Figure 1 shows a schematic diagram of a typical cross section of such a coating. Summary of the Invention [Problem to be solved by the invention]

[0007] Rotor blade tip coatings realized in this way may show poor layer adhesion. In the corresponding coating process, the energy input is relatively low and there is little interdiffusion at the interface between the coating and the substrate. Interdiffusion usually ensures a strong chemical bond or adhesion. As a result, due to the high centrifugal forces, breakage and detachment of the entire layer or abrasive particles may occur already during the blade rotation.

[0008] In addition, both the abrasive particles and the matrix used in the prior art are not resistant to oxidation at high temperatures and are damaged due to oxidation. The abrasive particles typically used have a particle size of the order of a layer thickness, and therefore can extend from the surface to the interface between the coating and the substrate. Once the particles are oxidized, the blade material or the corresponding interface can be easily and quickly attacked by oxidation. In addition, the matrix used in the prior art is prone to creep at high temperatures and becomes too soft to fix the hard abrasive particles.

[0009] As a result, improvements in rotor blade design and manufacturing methods are needed. [Means for solving the problem]

[0010] This problem is addressed by a gas turbine engine rotor blade having a coating at a tip of the rotor blade that includes an oxidation-resistant abrasive layer, the rotor blade tip having at least a portion of an orientation surface having a normal vector with a component in the direction of rotation of the rotor blade. Such rotor blade tips include an orientation surface disposed in a specific relationship to the direction of rotation.

[0011] The advantage of a rotor blade tip with such an orientation surface is that the force distribution on the rotor blade tip when cutting into an abrasive material is nearly perpendicular to the coating layer on the rotor blade tip. This reduces the risk of shearing or peeling off the coating layer, as can happen with prior art rotor blades that have lateral forces along the coating layer. Furthermore, the forces and friction are distributed over a larger area, reducing frictional heat and wear.

[0012] This advantage also applies to rotor blades with coatings created by other methods, such as PVD. PVD coatings are more adhesive and oxidation- and wear-resistant. In particular, the cathodic arc evaporation technique is particularly important for applying rotor blade tip coatings for the following reasons: A higher energy input of ions can be achieved by the cathodic arc evaporation technique, contributing to strong layer adhesion and dense coating structure, and the cathodic arc evaporation technique can realize the deposition of various materials and their combinations, can realize advanced layer structures, and therefore achieve unique coating properties. By designing the coating material and adjusting the coating parameters, the coating can be adapted to the needs of different substrate materials and applications. The cathodic arc evaporation technique is widely used in industry due to its high coating speed and production safety.

[0013] However, the tip friction behavior of PVD and electrolytically coated rotor blade tips is different. In the case of electrolytically coated rotor blade tips, hard extruded cubic boron nitride abrasive particles are embedded in the MCrAIX matrix of the flat rotor blade tip, as shown in Figure 1. They cut into the abradable coating by localized contact between the sharp corners and facets of the particles and the abradable coating. On the other hand, PVD coatings have an abrasive coating applied along the contour of the flat rotor blade tip, so that cutting into the abradable coating is by complete contact between the entire coated rotor blade tip surface and the abradable coating.

[0014] The friction, and therefore the frictional heat generated during a friction event, is much higher for PVD coatings compared to electrolytically coated blade tips due to the larger contact area between the coated rotor blade tip and the abradable coating. However, these thermal properties are the reason for the possible failure of the PVD coating on the rotor blade tip. It has been shown that high temperatures lead to an extreme increase in wear of multi-layer CrAIN PVD coated flat rotor blade tips (Watson, M., Fois, N. and Marshall, M.B. (2015), Effects of blade surface treatments in tip-shroud abradable contacts, Wear, Vol. 338-339, 15 September 2015, pp. 268-281, ISSN 1873-2577). It has been reported that due to the poor high temperature tribological properties of CR(Al)N PVD coatings, parts of the coating are torn off and remain stuck to the abradable material. These hard particles in the abrasive material would prevent wear, causing the rotor blade tip to wear faster, grinding away the coating, and exposing the underlying substrate to oxidation. This study also applied chamfers to the rotor blade tips, and the orientation plane of the chamfered rotor blade tip had a normal vector with a component opposite to the direction of rotation of the blade. With this modification, the CrAlN PVD-coated chamfered rotor blade tip had much better cutting performance, but the chamfered rotor blade tip still wore flat, removing the coating from the flank surfaces at and near the tip, so the coating could not protect the rotor blade tip from oxidation.

[0015] It is therefore known that rotor blade tips having coatings that produce higher layer adhesion, such as PVD coatings, usually suffer from higher wear and temperatures of the rotor blade tip coating, resulting in failure of the coating. Rotor blades having such coatings benefit in particular from the claimed rotor blade tips, since they significantly reduce frictional heat and wear.

[0016] In one embodiment, a rotor blade tip has a multi-layer coating including an oxidation resistant abrasive layer over a layer of MCrAlX, where M includes one or more of Ni and Co, and X includes one or more of Y and Hf.

[0017] In one embodiment, the oxidation-resistant abrasive layer comprises an oxide, a boride, a carbide, a nitride, or a mixture thereof.

[0018] In one embodiment, the orientation surface is convex or concave relative to the abradable coating during operation.

[0019] In one embodiment, at least a portion of the rotor blade tip is chamfered such that the chamfered orientation surface has a normal vector that has a component in the direction of rotation of the rotor blade.

[0020] In one embodiment, at least a portion of the rotor blade tip is chamfered with a chamfer angle between 1 and 30 degrees, and in another embodiment, the chamfered flat surface includes an edge radius between 5 and 200 μm.

[0021] In one embodiment, at least a portion of the rotor blade tip is curved such that the curved orientation plane has at least one normal vector that has a component in the direction of rotation of the rotor blade.

[0022] This problem is also addressed by a method having the features of claim 9. Some embodiments are explained in more detail with the help of the following figures. [Brief description of the drawings]

[0023] [Figure 1] 1 shows a coated rotor blade tip of the prior art. [Diagram 2] 1 illustrates one embodiment of a rotor blade tip coating. [Diagram 3] 1 shows front and side views of a rotor blade as well as a rotor blade tip. [Figure 4] 1 illustrates one embodiment of a rotor blade tip shape with interacting forces. [Diagram 5] 1 illustrates an embodiment of a rotor blade tip configuration. [Figure 6] 1 illustrates an embodiment of a rotor blade tip configuration. [Figure 7] 1 illustrates an embodiment of a rotor blade tip configuration. [Figure 8] 1 illustrates an embodiment of a rotor blade tip configuration. [Figure 9] 1 illustrates an embodiment of a rotor blade after penetration friction testing. [Figure 10] 1 illustrates blade wear for an embodiment of a rotor blade and a prior art rotor blade in a penetration rub test. [Figure 11] 4 illustrates temperatures of an embodiment of a rotor blade and a prior art rotor blade during a penetration friction test. [Figure 12] 1 illustrates one embodiment of a method for producing a rotor blade tip coating. [Figure 13] 1 shows an x-ray diffractogram of one embodiment of a rotor blade tip coating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Figure 1 shows a schematic diagram of a coated rotor blade tip according to the prior art. The coating is applied to a blade substrate 14 and typically comprises abrasive particles 13 (such as cubic boron nitride) embedded in an MCrAlX matrix 12. Such coatings are applied by electrolytic or electrophoretic deposition. It can be seen that possible wear processes occur primarily at the surfaces and edges of the abrasive particles 13 protruding from the MCrAlX matrix 12.

[0025] 2 shows a schematic diagram of one embodiment of a rotor blade tip coating 10 applied to a blade substrate 14 and including an intermediate MCrAlX layer 12 and an oxidation-resistant abrasive layer 11. The blade substrate 14 may be a superalloy such as a single crystal superalloy, for example CMSX4. The MCrAlX layer 11 acts as both an adhesive between the blade substrate 14 and the oxidation-resistant abrasive layer 11 and as an oxidation inhibitor layer.

[0026] The oxidation-resistant abrasive layer 11 can be an aluminum chromium oxide ceramic, which is already oxidized and therefore resistant to oxidation at high temperatures, and is also very hard, with a hardness of over 2000 HV according to the Vickers hardness test, making it very abrasive. Similarly, many other oxides, borides, carbides, nitrides and other ceramics work for the same reason that they are oxidation-resistant and abrasive. In the case of an oxidized layer, without the MCrAlX intermediate layer 12, there is a risk of oxidation of the lower blade substrate 14. Compared to the previous figure showing the state-of-the-art coating, it can be clearly seen that the area where possible wear occurs is much larger, since it occurs over the entire surface of the oxidation-resistant abrasive layer 11.

[0027] FIG. 3 shows a schematic of a front and side view of rotor blade 30 and a close-up of rotor blade tip 20 illustrating one embodiment of a rotor blade tip configuration.

[0028] The counterclockwise direction of rotation of rotor blade R is indicated by the arrows. For simplicity, a flat vertical profile has been assumed for the front and side views, thus simplifying the shape of rotor blade 30.

[0029] As an example, an IN718 blade may be selected as the rotor blade 30 having a rotor blade tip 20 with a width of 1 mm. Although a flat rotor blade tip shape is disclosed in the state of the art, one embodiment of the rotor blade tip shape is represented by a chamfered rotor blade tip. This chamfered rotor blade tip shape results in an oriented rotor blade tip surface 21 having a normal vector 22 with a component 23 in the direction of rotation of the rotor blade R. The normal vector 22 defines an orientation plane of the rotor blade tip 20 that can interact with the abradable coating 16, as described below.

[0030] 4 shows a schematic diagram of one embodiment of a rotor blade 30 having a rotor blade tip 20 that cuts into an abradable coating 16 of a turbine shroud 15. The orientation plane defined by a normal vector 22 is inclined toward the abradable coating 16 in the direction of rotation of the rotor blade R.

[0031] The rotor blades 30 may move into the turbine shroud 15, such as during thermal expansion or when the turbine is moved off-center due to vibration. Physically, the same occurs when the turbine shroud 15 moves into the rotor blades 30. Thus, the penetration test involves testing the interaction between the rotor blade tips 20 and the wear resistant coating 16 by moving the turbine shroud into the rotor blades at a penetration velocity v. However, the same physical processes occur as in an actual turbine in operation.

[0032] When the rotor blade tip 20 of the rotor blade 30 moves into the abradable coating 16 of the turbine shroud 15, or vice versa, the rotor blade tip experiences a force F from the penetrating movement into the abradable coating. v and the force F coming from the rotational movement into the abradable coating 16. r This results in a total force F Total results.

[0033] Total power F TotalThe direction of the penetration force F v and rotational force F r It depends on the proportion of. The advantage of the rotor blade tip 20 having at least a partial orientation surface 21 with a normal vector 22 having a component 23 in the direction of rotation of the rotor blade R is that in this case the total force vector F Total The advantage of this approach is that vector F is somewhat aligned with normal vector 22, e.g., they point in roughly opposite directions or have components that point in opposite directions. Depending on the shape of the orientation surface with normal vector 22, vector F Total A weighting of the vector components acting against the rotor blade R can be selected. In the illustrated embodiment, the orientation plane is a plane (i.e., a chamfered surface) that can be described on the normal vector 22. In other embodiments, as shown below, the orientation plane 21 has at least a local curvature such that the normal vector 22 locally describes the orientation. In any case, however, the orientation plane has some component 23 in the direction of rotation of the rotor blade R.

[0034] This results in a force distribution normal to the coating on the rotor blade tip 10 instead of lateral forces along the coating layer or against the side of the rotor blade tip 20 .

[0035] This significantly reduces the risk of shearing or peeling off of the coating layer. Furthermore, friction is distributed over a larger area, reducing local frictional heat and temperature-related wear processes of the coated rotor blade tip. Together, this can be a possible explanation for the performance improvement. The chamfered rotor blade tip shape shown should be understood as only one embodiment of the rotor blade tip shape and is not limiting.

[0036] Figures 5-8 show other embodiments of rotor blade tip geometries. In Figures 5 and 6, a chamfered rotor blade 30 is shown having a normal vector 22 with a component 23 in the direction of rotation of the rotor blade R. In Figures 7 and 8, a curved rotor blade is shown and one normal vector 22 of many possible normal vectors is shown, which has a component 23 in the direction of rotation of the rotor blade R. A corresponding abradable coating 16 on the turbine shroud 15 is also shown.

[0037] This indicates that the orientation surface 21 can be concave (eg, FIG. 7) or convex (eg, FIGS. 5, 6 or 8) relative to the abradable coating 16.

[0038] FIG. 9 shows an exemplary cross-sectional analysis of one embodiment of a rotor blade 30. In this example, the rotor blade tip 20 was coated with multiple layers consisting of an MCrAIY intermediate layer and an aluminum chromium oxide top layer. The rotor blade tip 20 is chamfered at a 10° angle. The figure shows the rotor blade tip 20 after a penetration rub test. The sample was cut in the center as shown by the dashed line. The arrow indicates the counterclockwise rotation direction of the blade R. It can be seen that the coating is intact after the rub test and covers all sides of the rotor blade tip.

[0039] FIG. 10 shows the blade wear as a percentage of the total penetration depth for three blade tip geometries, two of which are prior art and one of which is an embodiment of the claimed invention. The two prior art blade tip geometries are a flat blade tip geometry and a chamfered blade tip geometry with no orientation plane with a normal vector that has a component in the direction of rotation of the rotor blade. All rotor blade tips were coated with a multi-layer consisting of an MCrAIY intermediate layer and a chromium aluminum oxide top layer. It can be clearly seen that the blade tips according to an embodiment of the claimed invention show significantly lower wear (less than 1%) compared to the prior art blade tips (~25%).

[0040] Figure 11 shows the temperatures measured at the blade tips during the penetration rub test. The two prior art blade tips experienced a temperature increase of approximately 480°C and 160°C, respectively, while the blade tip embodiment did not experience any temperature increase.

[0041] One embodiment of the manufacturing method of the rotor blade tip coating 10 can be achieved by using deposition from the gas phase, in particular by a PVD process, which is exemplarily explained in more detail with the help of FIG.

[0042] The use of reactive cathodic arc evaporation is particularly preferred. By using reactive cathodic arc evaporation, the adhesion of the rotor blade tip coating 10 can be significantly improved, since the higher energy input of ions contributes to improved layer adhesion. The coating can also be adapted to the needs of different blade substrate materials 14 and applications. Different PVD coating materials can be used, either as single layers or composite multilayers, to provide the desired properties in terms of oxidation resistance, hardness and ductility at high temperatures. These materials may include oxides, borides, carbides and nitrides.

[0043] A coating of a structural MCrAIX intermediate layer 12 followed by an aluminum chromium oxide layer as an oxidation resistant polishing layer 11 is deposited on a rotor blade tip 20 made of a superalloy, for example CMSX4, as a substrate 14 .

[0044] The MCrAIX layer 12 is deposited from an MCrAIX material source or target by plasma enhanced cathodic arc evaporation. The MCrAIX layer 12 can have a thickness of 0.1-100 μm according to the required oxidation resistance. In the present example, the layer thickness is chosen to be 10 μm.

[0045] An oxidation-resistant polishing layer 11 is deposited on the MCrAIX adhesive and oxidation protection layer 12. The aluminum chromium oxide layer is deposited from a metallic AICr target by reactive cathodic arc evaporation in an oxygen atmosphere. The oxide layer 11 can be 0.5 to 50 μm thick. In this example, the layer thickness is chosen to be 10 μm.

[0046] The coating system is deposited on the rotor blade 30 using an arc deposition method. To apply the coating system to the rotor blade 30, using the claimed coating method, the rotor blade 30 is placed in a vacuum coating chamber 60. The rotor blade 30 is rotatably arranged in the center of the vacuum chamber on a carousel 61. The coating system can be deposited on the rotor blade 30 by using different amounts of targets, for example two, four or more targets, acting as cathodes. The order and number of targets can be of any desired type. The configuration shown in this particular example (FIG. 3) includes four targets 63, 64, 65, 66, all of which are configured to act as cathodes. The targets 63, 64, 65, 66 are attached to the wall of the vacuum coating chamber 60. To produce the coating system described in this particular embodiment, the cathodes 63 and 64 are targets containing MCrAIY as the main component, and the cathodes 65 and 66 are targets containing aluminum chromium (AICr) as the main component. The target positions are by way of example only and are not limiting. To generate an oxygen (O2)-containing layer, a non-zero amount of O2 is introduced into the vacuum chamber 60 through the gas inlet. In this embodiment, the O2 pressure is set to 1.0 10 -2The pressure was set at 1000 psi (mbar). As shown in Figure 3, an argon (Ar) gas inlet is also installed to use argon as a working gas. To produce a coating system, the coating temperature is selected in the range of 200-600 °C. A magnet, not shown in this figure, is placed behind the target, allowing the magnetic field to be adjusted to achieve changes in the coating properties. A shutter 62 can be installed in front of the targets 63, 64, 65, 66, allowing different layers to be coated, but is not required.

[0047] FIG. 13 shows an x-ray diffractogram of an exemplary oxidation-resistant polishing layer 11 that is aluminum chromium oxide.

[0048] Although the embodiments have been described in the context of plasma deposition processes, chemical vapor deposition can be used for at least some steps. [Explanation of symbols]

[0049] 10 Rotor blade tip coating 11 Oxidation-resistant polishing layer 12 MCrAlX layer 13 Abrasive particles 14 Blade base material 15 Turbine shroud 16 Abrasion-resistant coatings 20 Rotor blade tip 21 Oriented rotor blade tip surface 22 Normal vector of the oriented rotor blade tip surface 23 Components of the normal vector in the direction of rotation of the rotor blade 30 Rotor Blades 50 Gas Turbine 60 Vacuum Chamber 61 Carousel 62 Shutter 63 Coating Objects 64 Coating Objects 65 Coating Objects 66 Coating Objects Al Aluminum Ar Argon Co Cobalt Cr Chromium F v Penetration power F r Rotational Force F Total Total Strength Hf Hafnium M Metal N Nitrogen O2Oxygen R Rotor blade rotation direction v Intrusion speed X contains yttrium or hafnium or both Y Yttrium

Claims

1. 1. A rotor blade (30) for a gas turbine engine (50), characterized in that a coating (10) on a rotor blade tip (20) of the rotor blade (30) comprises an oxidation-resistant abrasive layer (11), and the rotor blade tip (20) at least partially has an orientation surface (21) having a normal vector (22) with a component (23) in the direction of rotation of the rotor blade (R).

2. 2. The rotor blade of claim 1, wherein the rotor blade tip further comprises an oxidation-resistant abrasive layer over the layer of MCrAlX, wherein M comprises one or more of Ni and Co, and X comprises one or more of Y and Hf.

3. The rotor blade (30) of claim 1, wherein the oxidation-resistant abrasive layer (11) comprises an oxide, a boride, a carbide, a nitride, or a mixture thereof.

4. The rotor blade (30) of claim 1, wherein, at least in part, the orientation surface (21) is convex or concave relative to an abradable coating (16) of a turbine shroud (15) during operation.

5. 2. The rotor blade (30) of claim 1, wherein the rotor blade tip (20) at least partially has an orientation surface (21) that includes a chamfered plane having a normal vector (22) with a component (23) in the rotational direction of the rotor blade (R).

6. The rotor blade (30) according to claim 5, wherein the orientation surface (21) comprises a chamfered plane having a chamfer angle of 1 to 30 degrees, in particular 5 to 15 degrees.

7. The rotor blade (30) of claim 5, wherein the chamfered flat surface includes an edge radius of 5 to 200 μm.

8. 2. The rotor blade (30) of claim 1, wherein at least a portion of the rotor blade tip (20) has a curved orientation surface (21) having at least one normal vector (22) with a component (23) in the direction of rotation of the rotor blade (R).

9. A method for manufacturing a rotor blade (30), wherein the coating (10) on the rotor blade tip (20) of the rotor blade (30) comprises an oxidation-resistant polishing layer (11), and the rotor blade tip (20) at least partially has an orientation plane (21) having a normal vector (22) with a component (23) in the rotational direction of the rotor blade (R), which is deposited by plasma vapor deposition and / or chemical vapor deposition.

10. The method of claim 9, wherein the plasma deposition method is cathodic arc evaporation.

11. 11. The method of claim 9 or 10, wherein the coating (10) is a multi-layer coating including an oxidation-resistant abrasive layer (11) over a layer of MCrAlX (12), where M includes one or more of Ni and Co, and X includes one or more of Y and Hf.

12. A gas turbine engine (50) comprising a rotor blade (30) according to at least one of claims 1 to 7.

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