JP2018535322A - Turbine clearance control coating and method - Google Patents

Abstract

The present invention is a turbine engine having a high pressure and low pressure turbine section comprising a casing and at least one turbine blade rotatably mounted in the casing, wherein at least a portion of the inner surface of the casing is at least one. In a turbine engine that is covered with a shroud as a wear material to provide clearance control between the inner surface and the tip of two blades and the tip of the blade is coated with a hard PVD coating, at least the high and / or low pressure sections Disclosed is a turbine engine characterized in that the shroud material comprises a porous ceramic-based material and the hard PVD coating on the blade tip consists essentially of a nitride coating that is essentially free of droplets.

Description

  The present invention relates to a gas turbine engine and a blade of the gas turbine engine. According to a first embodiment of the present invention, the disclosed blade includes a physical vapor deposition (PVD) thin film hard coating for cutting and shaping a clearance control coating for turbine seal applications. This coating results in improved wear resistance of the blades in contact with the sprayed CoNiCrAlY boron nitride, NiCrAl bentonite, and NiCrAl boron nitride clearance control coatings during frictional contact.

  Turbine engines typically incorporate on-axis turbine blades that are circumferentially surrounded by a turbine casing or housing. In general, the turbine casing close to the tip of the blade is lined with a plurality of wearable shroud materials (coating) made of, for example, a metal / ceramic material having high heat and erosion resistance. In many cases, the wearable surface material itself is somewhat rough. Therefore, the blade tip gap G is maintained to avoid contact between two opposing elements that may cause premature blade tip wear.

  The basic configuration is shown in FIG. 1 and shows a rotor disk 3 having blades 5 including a turbine casing 1, a blade root 7 and a blade tip 9. The wearable seal 11 and the tip gap G between the wearable seal 11 and the blade tip 9 are also shown.

  In order to minimize airflow leakage at the blade tip between the high pressure blade side and the low pressure blade side, the blade tip gap G should be chosen as small as practical.

  In order to realize such a system with a very small blade tip gap G, it is known in the art to use so-called squealer tips. U.S. Patent No. 6,053,077 discloses such a blade having a squealer tip. When used for the first time for running purposes, these tips come into contact with the wearable coating of the casing or housing, thereby achieving a minimum gap G. To form such a squealer tip, U.S. Pat. No. 6,057,059 has a special shape selected to cause the tip of the turbine blade to act like a cutting tool, cut the wearable substrate and thereby form. Disclosure. Unfortunately, the problem of wear damage still exists. Because these tips with special shapes tend to wear when they come into contact with a wearable substrate, often with a specific combination of blade tip speed and blade tip penetration rate into the wearable shroud material It is. This is especially true when special wear materials are used such as, for example, sprayed CoNiCrAlY boron nitride, NiCrAl bentonite and NiCrAl boron nitride.

  Another approach that is very similar is disclosed in US Pat. No. 6,057,028, and with the same objective as above, a patterned strip coating is used as an abrasive coating for an abrasive coating. The coating material utilized is selected from the group of zirconium, yttrium and / or aluminum oxide, and the material is applied by thermal spraying through a perforated mask mounted on the structural surface to be coated. Although US Pat. No. 6,057,056 states that this procedure will avoid post-deposition profiling or machining, the proposed process handles a significant amount of wear and wear damage to the above wearable material is important. Problem remains.

  In Patent Document 3, Linska et al. Discloses an abrasion-resistant coating on a blade tip manufactured by electrodeposition. These electrodeposition coatings appear to strengthen the blade tip and thus function effectively, but require additional manufacturing steps. Another disadvantage of electrodeposition of the wear protection layer is that only conductive material can be deposited by electroplating. This limits such coatings to relatively thick (e.g., 300-50 micron) metal or alloy layers and is often not sufficiently wear resistant.

  U.S. Patent No. 6,057,031 discloses a method for coating the tip of a wing, which uses a mechanical mask to expose only the tip region of the wing to the PVD coating. The disclosed thicknesses of stellite, carbide or nitride coatings are mentioned between 25.4 and 127 μm and they should ensure the desired thickness tolerance of the airfoil with respect to wear. As the most preferred and only example of a wear coating, cubic boron nitride is disclosed as a material that does not wear during operation and protects the structural integrity of the wing. The use of cubic boron nitride can be expected due to the generally known very high hardness, wear resistance, and oxidation resistance up to 1300 ° C. However, since the presence of hexagonal boron nitride is mainly observed, deposition on technical substrates is quite difficult. Also, the high stresses of PVD coatings that occur during growth generally limit the required coating thickness considerably and may make most PVD coated carbides or nitrides unusable for use as wing wear-resistant layers. There is.

  Accordingly, there is a need in the art for a blade having a blade tip that exhibits wear resistance to contact with the abradable substrate described above.

WO2015 / 041787 US5756217A US20150075327A1 US20150368786A1 EP0674020B1

  In accordance with the present invention, the blade tip is coated with a physical vapor deposited thin film coating, as is known, for example, in cutting tool applications.

  It is already known to use PVD coatings on turbine blades against corrosion and erosion by solid particles entrained in a gas turbine engine compressor. For example, U.S. Patent No. 6,057,051 describes a multilayer erosion resistant coating against such erosion by particles.

  However, according to the present invention, a PVD coating is used to reinforce the blade tip against wear resulting from interaction with the abradable substrate. There is severe wear damage resulting from excessive frictional heating of the blade material under the severe friction intrusion conditions of the turbine and / or when the wearable coating is sprayed to an excessively high bulk hardness state. The observed mechanisms are softening of the blade material due to heating, extreme bulk plastic deformation and fracture, and movement of the blade material to the stator shroud. Combustion of the blade material (mainly limited to titanium alloys) can also result in severe engine damage. For an abrasive shroud having a hardness higher than a certain value, the blade material cracks due to the extreme blade cutting forces that result from inefficient cutting.

  The focus of this disclosure is the two of the above blade materials with one or more metal alloy or metal alloy oxide material components with designated CoNiCrAlY-hBN, NiCrAl-bentonite, NiCrFeAl-hBN and NiCrAl-hBN wearable coatings. It relates to measures against body abrasive wear (hBN is used as an abbreviation for hexagonal boron nitride).

Intrusional friction events between the blades on the rotor against the stator (shroud) can result from a number of causes, for example:
・ Different thermal expansion effects between rotor and stator parts ・ Abrupt changes in engine condition or load, such as hard landing or sudden rise of aircraft ・ “Overheating” operating conditions ・ Rapid engine shutdown ・ Distortion due to out-of-roundness of casing Related factors-Rotor vibration due to bearing clearance and instability

  Under certain rotor penetration conditions of blade tip speed and blade penetration speed into the stator (shroud), blade tip wear damage can occur. Furthermore, if the clearance (wear) coating is sprayed at a hardness or density above its specified hardness, increased blade wear damage can occur over a wide range of penetration conditions that would otherwise not occur.

  The type of wear as a result of such events is very different from the damage caused by the corrosive impact that occurs when particles such as sand or dirt entrain in the gas stream enter the turbine and hit the blades. Please note that.

Therefore, the object of the present invention is, for example,
Elimination of wear damage caused by the above-mentioned events in titanium alloy compressor blades, nickel alloy compressor blades, and stainless steel compressor blades.

  According to the present invention, this is a blade surface that contacts an abradable clearance control coating (eg, CoNiCrAlY-hBN, NiCrAl-bentonite, NiCrAl-hBN, NiCrFeAl-hBN) during an ingress friction event in the compressor section of a turbine engine. And by applying a thin film physical vapor deposition (PVD) hard coating.

  In other words, according to the present invention, the PVD hard coating applied to the blade, particularly the blade tip, has the purpose of protecting against wear resulting from the interaction of the blade tip and the abradable substrate.

  Surprisingly, PVD coatings known from cutting tool applications are notably low pressure and high pressure compressor rotors, aero engine blisks, and titanium alloys, stainless steels used in industrial gas turbine compressor rotors. And / or when applied to a nickel alloy blade would be advantageously used in this context and would exhibit excellent protection performance.

  In the following, throughout this disclosure, the expression “tipping” will be used when referring to providing a coating at least at the tip, preferably also around the blade tip. In order to define the word “periphery”, according to the invention, a point on the blade surface is defined as the coating thickness from the outermost part of the blade where it is attached (as viewed from the axis of rotation) If it is at a distance not exceeding 100 times the length, it is regarded as a part of the periphery of the blade tip.

  To date, it is not known in the art to apply a PVD coating to the blade tip for tipping purposes. Blades are generally used without any tipping as the most economical solution (in terms of production).

  On the other hand, when tipping is used, known techniques are generally limited to thicker hard coatings, such as coatings deposited by thermal spray techniques such as atmospheric plasma spray (APS) and high velocity oxygen fuel (HVOF) spray. The Coatings applied by these techniques are generally 100-200 micrometers thick and have the following disadvantages:

-Insufficient adhesion to blade tip material. APS and HVOF coatings are mechanically bonded to the surface to be coated.
-Especially for thin blade tips used in high pressure air compressors, the coating dimensions (thickness) and weight are too large.
-Preparation of the material to be coated requires surface roughening (eg grit blasting), which can compromise the mechanical integrity of the blade component.

  In contrast, coatings deposited at the tip by PVD technology are primarily metallurgically bonded to the substrate material, have a very high bond strength, and can cause adverse effects on the blade material Is very hard and oxidation resistant. According to the present invention, the tip coating deposited by PVD can be applied to the blade tip as a very thin layer. For example, a thickness of 1-40 microns, preferably 5-25 microns, with the advantages of controlled intrinsic coating stress and moderate surface roughness. At the same time, the PVD coating exhibits high density and wear resistance.

  Tipping a blade with a PVD coating according to the present invention may, for example, be a thin (eg 1 to 40 micron thick) hard (eg 1000 to 3500 HV intrinsic film hardness) PVD at and / or around the tip of the blade. Coatings such as titanium nitride (TiN), titanium aluminum nitride (TiAlN), titanium silicon nitride (TiSiN), titanium carbon nitride (TiCN), chromium nitride (CrN) or aluminum chromium nitride (AlCrN), It also means that a combination of these can be applied. These are hard coatings typically used in the context of cutting tools.

  Very surprisingly, we have made these PVD coatings, especially hard thin film PVD coatings as typically used in the field of cutting tools, under a wide range of blade penetration conditions into the shroud. It has been found that blade wear damage can be reduced and / or eliminated. More surprisingly, as noted above, these nitride-based coatings are known to be significantly less resistant to oxidation at high temperatures (eg, than oxide or cubic boron nitride) The mentioned nitride-based coatings do not undergo premature oxidation.

  I don't fully understand why this works. However, as one possible explanation, it can be said that the state present in the interaction between the blade tip and the wearable surface is substantially similar to the state when the high speed cutting tool is acting on a metal alloy workpiece. Let's go.

1 is a schematic view of an industrial or aerospace turbine comprising at least one blade 5 on a rotor disk 3 having a blade root 7 and a blade tip 9 and an abradable seal 11. The abradable seal 11 is arranged inside the turbine casing 1 on the opposite side of the blade tip 9 and is separated by a gap G. 1 schematically represents a uniform coating thickness distribution on and around the coated blade tip region 9.

  Hereinafter, the present invention will be described in detail using examples.

  We are based on research on a wide range of wearable materials. Although they are well coated (eg on a housing), a stack of these materials is termed a coating shroud to clearly distinguish it from PVD coatings.

  The test is based on the following shroud coating material.

1. Ni4Cr4Al21 bentonite Product name: Durabrade 2313, Metco 314NS, Metco 312NS, Durabrade 2311

  These are cermet powders consisting of a nickel chromium aluminum alloy that completely encapsulates a stabilized bentonite core. Encapsulation is achieved using a chemical cladding method. This gives a composite powder that is durable and free of high quality binders. This powder was designed to produce substrates with various corrosion and wear resistances to suit the end use. The substrate is designed to rub against nickel-based alloy or steel hardware.

  2. CoNiCrAlY-hBN-polyester

  The CoNiCrAlY (cobalt-nickel-chromium-aluminum-yttrium) matrix within the substrate of these materials provides improved oxidation and corrosion resistance compared to other nickel-chromium based wear materials. The boron nitride component provides solid lubrication, thereby improving wear and reducing blade wear during rubbing. The porosity of the substrate can vary in the range of 35-60% by volume. This is controlled by the amount of polyester encapsulated in the coating. It is this controlled web-like metal structure that allows excellent friability for titanium alloy, steel or superalloy parts.

  These substrates can be used at service temperatures up to 750 ° C. (1380 ° F.). However, above 650 ° C. (1200 ° F.), the sensitivity to oxidation is expected to increase. A hard tip mating blade or knife edge is recommended when used in extreme environmental conditions or when a hard and highly corrosion resistant coating is required. Metco 2042 and Metco 2043 coatings are easily scratched by bare, untreated nickel alloys and stainless steel parts at service temperatures up to 650 ° C. (1200 ° F.). For use with bare, untipped titanium parts, Metco 2042 is recommended at service temperatures up to 550 ° C. (1020 ° F.).

3. NiCrFeAl-hBN
Product name: Metco301C-NS and Metco301NS, ie Ni13Cr8Fe6.5BN3.5Al2.

  Nickel-chromium alloy / boron nitride spray powder is a cermet composite material consisting of nickel-chromium alloy, hexagonal boron nitride, and aluminum, and is manufactured using mechanical cladding techniques. This powder was designed to produce substrates with various corrosion and wear resistances to suit the end use. The powder is best applied using a combustion powder spray process that uses either hydrogen or acetylene as the fuel gas.

4). Aluminum Bronze Polyester Product Name: Metco 604NS, Metco 605NS, Metco 610NS

  Metco 604NS, Metco 605NS, and Metco 610NS are powder materials designed to produce abradable substrates for aerospace and industrial turbine clearance control applications that operate in marine environments where salt corrosion is a concern. The metal matrix of these powders is a pre-alloyed aluminum bronze material. A specially formulated polyester material is combined with an aluminum bronze matrix material to form a low density substrate structure. In the case of Metco 604NS and 605NS, the polyester is mixed with the metal component. Metco 610NS is a composite material in which a polyester component is coated on a metal component using a solid organic binder.

  For NiCrAl-hBN-polyester, reference is made to substrates such as those described in US patent application: WO2011 / 094222A1 (Dorfman, Wilson et al.).

  In order to demonstrate the technical effect of the present invention, an evaluation program was implemented in a frame that tested the performance of the TiAlN coating deposited on the blade tip using the Oerlikon Balzers physical vapor deposition (PVD) process. Therefore, TiAl6V4 and Inconel 718 blades were tip coated with TiAl and subjected to penetration testing on specific Oerlikon Metco wearable substrates.

A TiAl6V4 alloy blade whose tip was coated with TiAlN was rubbed at 450 ° C. against the following.
1) M2042 wearable substrate: standard and high hardness levels HR15Y 39 and 69, respectively, and 2) M314NS wearable substrate: standard hardness level HR15Y50

Further, an IN718 alloy blade whose tip was coated with TiAlN was rubbed at 750 ° C. against the following.
1) M2043 Abrasion hardness HR15Y 67
2) M314 wear hardness HR15Y 50
All wearable substrates were sprayed at Oerlikon Metco (OM-CH) location in Switzerland.
A series of 16 penetration tests were conducted at the penetration test facility at Oerlikon Metco (OM).
The tests were performed at speeds of 250 and 410 m / s and the penetration speed tested was either 5 or 500 μm / s. The penetration depth reached was 1.0 mm.

  Under the given test conditions, bare titanium alloy blades typically experience significant wear against Metco 2042 and Metco 2043 wear materials (mainly low blade tip speed and high penetration rate). In contrast, TiAlN tipping showed improved wear performance so that no blade wear was observed. That is, the blade wear was 0%. This is measured as a percentage of the total penetration depth of the blade tip into the wearable coating shroud (1.0 mm nominal). Slightly negative blade wear values (eg -1.0%) may have been obtained, but this indicates a slight movement of the shroud material to the blade tip and damage to the blade tip or tip coating Is not observed.

  Metco 314NS also showed blade wear when rubbed using a bare TiAl6V4 blade without tipping. However, after tipping these blades with TiAlN, penetration tests showed improved friction performance without blade wear.

  This program clearly shows that application of a thin hard PVD coating to the blade tip (eg, titanium alloy and nickel alloy blade tips, etc.) can observe a dramatic reduction in blade tip wear damage, at least 70HR15Y It shows improved cutting performance in certain wearable (clearance controlled) substrate materials sprayed to hardness values up to (the postpolymer is burned in the heat treated state).

  A second embodiment of the present invention relates to an abradable coating used in high pressure compressor clearance control applications such as air turbines, industrial gas turbines and turbochargers. Related blade materials are, for example, titanium alloys, stainless steel alloys and nickel-base superalloys.

  State-of-the-art wear materials for these applications are generally metal alloys with poor thermal stability and exhibit low oxidation and / or sintering resistance. They are intentionally made softer and more porous to reduce blade damage. Here, in many cases, the blade has no protective tipping. As a result, an abradable material having a low bulk hardness is obtained. The porosity of the wearable coating is particularly susceptible to high temperature oxidation due to the larger exposed surface area of the metal alloy. Furthermore, the required higher porosity reduces the tensile strength of the coating and reduces erosion resistance. In particular, when the focus is on high temperature applications, the disadvantage is that these materials are generally not heat resistant.

  According to the state of the art, there are thermally stable zirconia-based polyester ceramic spray powders. It is commonly used as a high temperature wear coating for clearance control applications in the aerospace industry and the turbine section of industrial gas turbine engines. Here, the blade alloy is generally manufactured from a nickel-based superalloy. In addition, porous, refractory nickel and cobalt alloy based coatings are also used in the high pressure compressor area of the aerospace industry and industrial gas turbine engines, and blade alloys are either titanium alloys, stainless steels or nickel based superalloys. Manufactured from. However, for the majority of higher temperature sealing applications, each blade tip has a well-established electroplating and bare titanium because stainless steel alloys or nickel alloys exhibit excessive wear against these hard ceramic wears. Must be covered with cubic boron nitride abrasive particles applied using high temperature brazing techniques such as alloys. In addition, particularly when titanium alloys are used, there is a potential for a titanium fire when worn against a hard wear-resistant coating.

  The first embodiment described above discloses a hard thin film coating applied to the blade tip to protect against wear induced by the wear material. Surprisingly, the inventors further have a high temperature resistant shroud material (sprayed porous zirconia oxide or magnesium aluminate) when the bare blade tip is coated with a hard, wear resistant thin film coating. It has been discovered that even other porous low density ceramics (such as magnesium spinel) can be used as shroud materials that do not damage the blade tip. This makes thermal stable (high melting point, high oxidation resistance) ceramic or intermetallic based clearance control materials special in both low and high pressure compressor areas for aircraft turbines, industrial gas turbines and turbochargers. Can be used for

The current state of the art for high pressure compressor clearance control (wearability) applications are wearable coatings such as:
• Bulk hardness is lower (softer) than ceramic wear materials.
• More porous than ceramic wear materials.
A general metal alloy that has lower thermal stability (oxidation and sintering resistance) than ceramic.

  They need to be manufactured in a softer and more porous state to reduce blade damage (often without protective tipping on the blade). On the other hand, it is known to coat the tip of the blade in order to eliminate damage (wear) of the blade. PVD thin film coatings such as TiAlN and AlCrN deposited on the tip of the blade are used in turbomachinery.

Examples of blade materials are as follows.
-Titanium alloy, for example, TiAl6V4, Ti6242, γTiAl type (Ti-45Al-8Nb).
Stainless steel alloy, for example 17-4PH steel.
A nickel-base superalloy, such as Inconel 718.

  Thin film hard coatings have a very high wear protection effect, so harder wearable shroud materials (eg sprayed porous zirconia oxide) with higher thermal stability (high melting / sintering resistance, high oxidation resistance) The present inventors have now discovered that a coating, such as Metco 2460 (M2460), can be used advantageously.

  A TiAlN coating was deposited on the blade tip (Inconel 718) using a physical vapor deposition (PVD) process. The intrusions tested against two different sets of Metco 2460 NS wear coatings were sprayed. Two penetration tests were conducted at the penetration testing facility. The first test was rubbed with a TiAl blade tip coating onto a hard-plate plasma sprayed M2460NS coating, and the second test was performed with another set of M2460NS coatings plasma sprayed using standard spray parameters. went.

Both tests were conducted as follows:
-Blade tip speed 410 m / s.
-The penetration rate is 50 μm / s.
-Shroud temperature 1100 ° C.
-The penetration depth is 0.2 mm or 0.5 mm.

  M2460NS is a zirconia based polyester ceramic spray powder. This is commonly used as a high temperature wear coating for clearance control applications in the aerospace industry and industrial gas turbine engine turbine parts as previously mentioned, and in the prior art cubic boron nitride is the blade material. used.

  The following two variants of this coating were produced by thermal spraying and heat treated to burn the polyester porous former.

  High hardness M2460NS: Macro hardness was measured with an average of 59HR15N (polymer burnout state). The M2460NS wearable coating sample was tested after polymer burnout (550 ° C / 6h). A test run using a blade tip speed of 410 m / s and an intrusion speed of 50 μm / s showed good friction performance without blade wear.

  Standard hardness M2460NS coating: Macro hardness was measured with an average of 36HR15N (polymer burnout state). This M2460NS wearable coating sample was tested after polymer burnout (550 ° C./6 hours). Tests using a blade tip speed of 410 m / s and penetration speed of 50 μm / s have no blade wear and relate to an increase in surface blade height (2.1% increase in blade height as a percentage of penetration depth) And showed good friction performance.

  When performing penetration tests on the M2460 shroud, typical blade wear seen with non-tip (uncoated) Inconel 718 blades is in the range of 70-100% wear as a percentage of the total penetration depth. Typically, zero blade wear is seen for Inconel 718 blades chipped with state-of-the-art cubic boron nitride when penetration testing is performed on the M2460 shroud.

  Surprisingly, the area seen for a TiAlN coated blade tip is similar to the area seen for a state-of-the-art cubic boron nitride chip blade. That is, zero blade wear as a percentage of the total penetration depth.

  Based on these results, if the tip is coated with AlCrN, the range is presumed to be at least equivalent, even if not more. In particular, AlCrN may be preferable in the high temperature range. Perhaps this will return to the improved temperature stability of this PVD coating.

  Post penetration test (cut) The surface roughness of the shroud surface was measured and compared with cutting using a commercially available standard blade tip (abrasive cubic boron nitride). The results (shown in Tables 1 and 2 below) indicated that PVD-bladed blades produced a smoother and lower surface finish. Such improvements are important for aerospace clearance control applications in all parts of the aero turbomachine (compressor and turbine).

Table 1 shows the M2460 NS shroud roughness after intrusion for a blade with a PVD chip of the present invention.

Table 2 shows the M2460 NS shroud roughness after intrusion for blades chipped with cBN according to the prior art.

Improvements observed by the use of TiAlN and / or AlCrN PVD coatings on the blade:
• Blade wear was reduced to zero compared to non-tip blades (typically blade wear is 70-100% of total penetration depth).
Equivalent blade wear (zero) as observed for blades chipped with prior art cubic boron nitride.
-The surface roughness of the shroud was improved compared to that observed for blades chipped with prior art cubic boron nitride.
It has lower cost, lower dimensions (coating thickness) and higher manufacturing robustness than those observed with blades chipped with prior art cubic boron nitride. In particular, the fact that thinner blade tips with complex tip shapes are more easily coated with PVD technology offers significant advantages over the state of the art.
Because of the ease of molding and coating of nickel superalloy and stainless steel blade materials using hard thin film PVD coatings, these are now porous ceramic systems for use in the high pressure compressor section of turbomachinery Wearable materials can be used,
i) Oxidation resistance ii) Sintering resistance iii) Great performance advantages over prior art high pressure compression wear materials (metal alloy base) in terms of corrosion resistance.
A porous ceramic-based wear material currently used in low pressure compressor parts of turbomachines because it is easy to coat other blade materials such as titanium alloys using a hard thin film PVD coating The opportunity to use is open and has the following great advantages:
i) Corrosion resistance ii) Improved thermal expansion imbalance and residual stress compatibility compared to wear members (typically aluminum alloy base) of prior art low pressure compressors.

  It has been disclosed that the combination of a blade tip coated with a hard film and a thermally stable porous ceramic shroud as a wear member is advantageous over the prior art. The hard thin film coating preferably comprises a composite material such as Me1Me2X. Me1 is preferably a member of the group formed by Ti, Cr, Zr or combinations thereof, Me2 is preferably Al and / or Si, and X is preferably N, O, B or their An element of a group formed by a combination. Those skilled in the art know many ways to efficiently apply such coatings to the blade tips, among which physical vapor deposition such as cathodic arc vapor deposition or sputtering is preferred.

  In accordance with another aspect of the present invention, a method for coating a blade with a hard thin film coating is disclosed. This aspect relates not only to the protection of the blade tips and the wearable shroud, but also to the protection of the blades against erosive particles (eg dust impingement at high speeds and multiple angles of incidence on the blade surface). To do.

  As already mentioned above, one of the preferred methods for applying such a thin film coating to the blade surface is physical vapor deposition. Examples include cathodic arc evaporation and sputtering. Typically, cathodic arc evaporation provides a very dense and hard layer, which is advantageous in applications related to the present invention.

  Density can be achieved when the deposited particles are highly positively charged. By applying a negative bias voltage to the substrate, these ions are accelerated to the surface to be coated. However, because of the so-called droplets that are typically generated during arc evaporation, deposited on the surface, and incorporated into a thin film, the resulting coating generally has a significant surface roughness.

  As already explained in the context of coating the tip, such roughness may be disadvantageous. Apart from this, the surface roughness of the blade surface creates multiple centers where erosion particles can attack and creates multiple erosion centers that naturally weaken protection against erosion. Furthermore, surface roughness adversely affects the flow in the turbine in an accidental and difficult to control manner.

  There are techniques that substantially prevent such droplets from being deposited or entrained on the thin film or its surface during cathodic arc evaporation. For example, a filtered arc can be used. Here, magnetic and / or electric fields are used to influence the flight of the deposited charged particles. Since the droplets are uncharged or predominantly macroscopic and have to be accelerated considerably, the coating particles are separated from the droplets on the way to the substrate to be coated.

  Sputtering is another preferred method of applying a thin film to a substrate based on physical vapor deposition. In the context of sputtering, so-called working gas ionized particles are accelerated onto the surface of the sputtering target. When these ions collide with the target surface, particles of the target material jump out.

  The acceleration of the ionized working gas particles is based on a negative voltage applied to the target. Since the impact of the target along with these particles heats it, the energy density with which the target can generally operate is limited. Sputtered thin films exhibit less surface roughness compared to thin films deposited by cathodic arc evaporation because no droplets are formed during deposition. In general, however, the sputtered particles are not charged or the degree of ionization is at least very low. Thus, these particles may not be accelerated in the direction of the surface to be coated once they leave the surface of the material that provides the target. The inventors of the present invention have found an idea to use and use special PVD coating methods for coating blades. The method results in a high density thin film without introducing droplets into the film.

  Each method is based on sputtering, but the energy density at which the sputtering process is performed increases dramatically compared to conventional sputtering. Such an increase can result in charged particles being emitted from the target surface and thus applying a negative bias to the substrate to be coated to accelerate the charged coating particles in the direction towards the substrate. it can. The heating of the target can be avoided by periodically interrupting each voltage to the target at a high frequency.

  This so-called HIPIMS is a sputtering method as described above, but has the disadvantage that a complex generator is required that provides a high output pulse that is well shaped at high frequencies and provides high reproducibility. In the context of another sputtering method developed by the applicant, the power is not switched off but simply switched to a different target and / or power dump. Applicant provides this method under the trademark “S3p”. A detailed description of an example of performing each sputtering method can be found in patent application WO2013 / 060415A1.

  According to one aspect of the present invention, the coating particles can be accelerated to the following speed. That is, when the coating particles are applied to the surface, they have a speed on the same order as the expected average speed of the dust particles impinging on the surface during use of the blade.

  Preferably, the hard thin film coating is produced by HIPIMS, particularly preferably by S3p and comprises a composite material such as Me1Me2X. Here, Me1 is preferably a member of the group formed by Ti, Cr, Zr or combinations thereof, Me2 is preferably Al and / or Si, and X is preferably N, O, B Or a group of elements formed by a combination thereof.

  All PVD coatings mentioned in the above description may be single or multilayer coatings. They can be applied with an adhesive layer between the turbine blade substrates, but can preferably be applied directly onto the substrate material itself. In the case of multiple layers, an intermediate layer (eg, a metal intermediate layer) can be foreseen. It is also possible to have one or more layers that contain gradients in the material composition as a function of coating depth. However, a single layer is preferable, and an AlCrN single layer is particularly preferable.

  It is also possible to coat the blade body surface with another coating compared to the blade tip. For example, all exposed surface portions of the blade can be coated with a coating used on the blade tip. This is preferably an AlCrN monolayer. After this, the tip can be masked and other surface portions can be coated, and in addition, a softer thin film material can be applied for the dust particles to strike the surface.

  The turbine engine includes a casing and at least one turbine blade rotatably mounted within the casing, wherein at least a portion of the casing inner surface provides clearance control between the inner surface and the tip of the at least one blade. Disclosed is a turbine section that is coated with a shroud as a wear material for and a blade tip is coated with a hard PVD coating, the shroud material comprising at least a porous ceramic based material, preferably a porous ceramic based It is characterized by being a material.

  The PVD coating may be a coating comprising a composite material such as Me1Me2X. Here, Me1 is preferably a member of the group formed by Ti, Cr, Zr or combinations thereof, Me2 is preferably Al and / or Si, and X is preferably N, O, B Or a group of elements formed by a combination thereof. The shroud material can include at least a zirconia-based polyester ceramic material, and is preferably a zirconia-based polyester ceramic material.

A method for manufacturing a turbine engine according to the turbine engine as described above is disclosed.
-Spraying the shroud material on the inner surface of the casing;
-PVD coating at least the tips of the blades used in the casing.

The PVD coating step can be performed by high power impulse magnetron sputtering with a power density pulse of 5 W / cm ² or more, preferably 50 W / cm ² or less, more preferably 40 W / cm ² or less, most preferably 30 W / cm. cm ² or less.

  The power can be supplied by a DC power generator, and the pulses are realized by switching power from one material that supplies the sputtering target to another material and / or a dummy target.

  Surprisingly, the PVD coating 95 produced by high power impulse magnetron sputtering further shows a uniform coating thickness distribution with an average coating thickness t measured at the blade tip 9 and a maximum deviation of about 10%. Yes. The coating thickness and high uniformity of properties apply not only around the turbine blade, but also along the coated corner between the blade tip 9 and the turbine blade mantle surface 91, as shown in FIG. It has been found that coatings that are essentially free of droplets exhibit a very dense structure that reduces the possibility of coating failure during operation. This feature is responsible for the high durability of PVD coatings on metal or ceramic shroud materials and is believed to be largely unaffected by their pore volume.

  Several variants of the PVD coating of the present invention, such as Ti50Al50N, Ti40Al60N, Ti33Al67N, and Al50Cr50N, Al60Cr40N, Al70Cr30N were deposited to achieve a good coating thickness distribution as well. The best performance results were achieved when PVD coating 95 exhibited a Me2 content of 40-70 at%, as calculated from Me1Me2X Me2 / (Me1 + Me2), where only the metal component of the coating was considered.

  It has been found that the PVD coating of the present invention can be deposited as a thin layer (e.g., 1-40 microns, preferably 5-25 microns thick).

DESCRIPTION OF SYMBOLS 1 Turbine casing 3 Rotor disc 5 Blade 7 Blade root 9 Blade tip 11 Wear seal 91 Mantle surface 95 PVD coating G Gap

Claims (9)

A turbine engine having at least a high pressure and a low pressure turbine section comprising a casing and at least one turbine blade rotatably mounted in said casing,
At least a portion of the inner surface of the casing is covered with a shroud as a wear material to provide clearance control between an inner surface and a tip of the at least one blade;
In a turbine engine in which the tip of the blade is coated with a hard PVD coating,
The shroud material of the at least high pressure and / or low pressure section comprises a porous ceramic-based material, and the hard PVD coating on the tip of the blade consists essentially of a nitride coating free of droplets. Turbine engine. An essentially droplet-free PVD coating is a coating comprising a composite material such as Me1Me2X,
Here, Me1 is preferably a member of the group formed by Ti, Cr, Zr or combinations thereof, Me2 is preferably Al and / or Si, and X is preferably N, O, B The turbine engine according to claim 1, wherein the turbine engine is a group of elements formed by a combination thereof. The PVD coating essentially free of droplets consists of the composite material Me1Me2X,
2. The turbine engine according to claim 1, wherein Me 2 is preferably Al and / or Si, and Me 2 / (Me 1 + Me 2) is in a range of 40 to 70 at%.   4. The coating essentially free of droplets has a coating thickness of 1 to 40 [mu] m, preferably a coating thickness of 5 to 25 [mu] m. Turbine engine.   5. The turbine according to claim 1, wherein the shroud material of the high-pressure and / or low-pressure section comprises at least a zirconia-based polyester ceramic material, preferably a zirconia-based polyester ceramic material. engine. A method for manufacturing a turbine engine according to any one of claims 1 to 5,
-Spraying the shroud material onto the inner surface of the casing;
-PVD-coating at least the tip of the blade used in the casing. As an additional step,
-Masking the tip of the blade;
The manufacturing method according to claim 6, further comprising: PVD coating the blade body with a coating different from the tip coating of the blade. The PVD coating process is performed by high power impulse magnetron sputtering with a power density pulse of 5 W / cm ² or more, preferably 50 W / cm ² or less, more preferably 40 W / cm ² or less, and most preferably 30 W / cm ² or less. The manufacturing method according to claim 6, wherein the manufacturing method is performed.   9. Manufacturing according to claim 8, characterized in that the power is supplied by a DC power generator and the pulses are realized by switching power from one material supplying the sputtering target to another material and / or a dummy target. Method.

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