A porous abradable seal coating and a method of making the same

Abstract

The present application provides a kind of porous abradable seal coating and its preparation method, the porous abradable seal coating includes base phase coating and spherical hole, the spherical hole is uniformly distributed in the base phase coating, the aperture of the spherical hole is 10-150 μm.The porous abradable seal coating provided by the present application has spherical hole, and the spherical hole is not easy to densify in the surface in the abrading process, in the abrading process, the place where coating is impacted and rubbed because the existence of spherical hole occurs crushing and produces retreat, and does not affect the combination of other places of coating, thus improves the abradability of coating, so that the abradability of coating can be maintained well in the whole service process, prolongs the service life of coating.

Description

Technical Field

[0001] This invention relates to the field of mechanical coating preparation, specifically to a porous wearable sealing coating and its preparation method. Background Technology

[0002] High-performance aero engines have higher requirements for efficiency and safety, and the clearance between the casing and the blade tip is a key factor affecting engine performance. To ensure high engine efficiency, this clearance should not be too large. However, if the clearance is too small, factors such as centrifugal force and surge during engine operation can cause the blade tip to rub against the inner wall of the casing, damaging the blade tip. Therefore, wear-resistant sealing coatings are often used to achieve air passage sealing and protect the blade tip.

[0003] Currently, commonly used abrasive porous sealing coatings are mainly prepared by thermal spraying. The resulting coatings have low porosity, which is not conducive to improving abrasiveness. Furthermore, the pore structure in the coating is mainly lamellar pores. When lamellar pores are rubbed during service, they are prone to surface densification, which leads to the abrasiveness being time-sensitive and reduces the service life of the coating. Summary of the Invention

[0004] The purpose of this invention is to provide a porous wearable sealing coating and its preparation method, wherein the coating has high wearability, thereby achieving the purpose of protecting the blade tip.

[0005] This invention is achieved through the following technical solution:

[0006] A porous wearable sealing coating comprising a base phase coating and quasi-spherical pores, wherein the quasi-spherical pores are uniformly distributed within the base phase coating and the pore diameter of the quasi-spherical pores is 10–150 μm.

[0007] Preferably, the base phase coating comprises a first solid phase and a second solid phase, wherein the first solid phase is distributed in the second solid phase; the first solid phase is Ni, NiO, Al or Zn; the second solid phase is YSZ or MCrAlX alloy, wherein M represents Ni or Co or NiCo alloy or CoNi alloy, and X represents a metallic element with stronger reducing power than Al.

[0008] Preferably, the porosity of the spherical pores formed within the base phase coating is 40% to 70%.

[0009] The method for preparing the porous wear-resistant sealing coating includes:

[0010] (1) Prepare a first powder, the first powder having a composite structure, the composite structure including a coated inner core and a coated outer shell covering the outer surface of the coated inner core, the melting point of the coated outer shell being lower than the melting point of the coated inner core;

[0011] (2) The first powder and the second powder are thermally sprayed onto the substrate to form an initial coating; wherein, during thermal spraying, the outer shell of the first powder is completely or partially melted, while the inner core is not melted;

[0012] (3) The initial coating is oxidized in an oxygen-containing atmosphere and at a preset temperature, and the inner core is evaporated after oxidation to form the porous wearable sealing coating.

[0013] Preferably, in step (1), the outer shell is a metal or metal oxide with a melting point below 2100°C; the inner core is a metal material with a melting point above 1500°C.

[0014] Furthermore, the outer shell is made of Ni, NiO, Al, or Zn; and the inner core is made of Mo.

[0015] Preferably, in step (1), the second powder is a YSZ or NiCrAlY alloy.

[0016] Preferably, in step (1), the volume of the second powder accounts for 20-80% of the total volume of the first powder and the second powder.

[0017] Preferably, step (2) specifically involves: mixing the first powder and the second powder to obtain a mixed powder, and then thermally spraying the mixed powder onto the substrate; or, thermally spraying the first powder onto the substrate separately, while simultaneously thermally spraying the second powder onto the substrate separately.

[0018] Preferably, in step (3), the preset temperature is 600-800℃.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The porous abrasive sealing coating provided by this invention has spherical pores. The spherical pores are not prone to surface densification during the abrasion process. During the abrasion process, the area of ​​the coating that is rubbed will be crushed and retracted due to the presence of the spherical pores, without affecting the bonding of other parts of the coating. That is, "it breaks wherever it is touched", thus improving the abrasiveness of the coating, so that the coating can maintain good abrasiveness throughout the service life and extend the service life of the coating.

[0021] This invention provides a method for preparing a porous, abrasion-resistant sealing coating. The method uses a first powder and a second powder comprising a composite structure as raw materials to prepare the porous, abrasion-resistant sealing coating. The composite structure includes an outer shell and an inner core. The melting point of the outer shell is significantly lower than that of the inner core. During thermal spraying, the first powder covering the outer shell partially or completely melts, while the second powder may or may not melt, and the inner core does not melt. The inner core oxidizes and volatilizes during subsequent high-temperature treatment, leaving a spherical pore structure in the coating, thus forming a porous, abrasion-resistant sealing coating. This invention's preparation method results in a coating with higher and controllable porosity and a more uniform pore distribution. Increasing porosity can reduce hardness and improve abrasion resistance. The coating with spherical pores prepared by this invention does not undergo surface densification during abrasion and maintains excellent abrasion resistance throughout its service life, extending the coating's service life. Attached Figure Description

[0022] Figure 1 The following are schematic diagrams of two composite powder structures provided by the present invention: (a) A represents the outer shell and B represents the solid inner core; (b) A represents the outer shell and B represents the agglomerated inner core.

[0023] Figure 2 The second powder surface and cross-section SEM images provided in Embodiment 1 of the present invention;

[0024] Figure 3 The structure diagram (a) of the initial coating before high-temperature oxidation and the structure diagram (b) of the porous wearable sealing coating after high-temperature oxidation provided in Embodiment 1 of the present invention; wherein: 1. substrate, 2. semi-molten or molten outer shell, 3. unmelted second powder.

[0025] Figure 4 The structure diagram (a) of the initial coating before high-temperature oxidation and the structure diagram (b) of the porous wearable sealing coating after high-temperature oxidation provided in Embodiment 9 of the present invention; wherein: 1. substrate, 2. semi-molten or molten outer shell, 3. molten second powder.

[0026] Figure 5 The porosity of the porous wearable sealing coating in Embodiment 1 of the present invention before wear is 44%. Detailed Implementation

[0027] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0028] The porous wearable sealing coating of the present invention comprises a base phase coating and quasi-spherical pores, wherein the quasi-spherical pores are uniformly distributed within the base phase coating and the pore diameter of the quasi-spherical pores is 10-150 μm.

[0029] The base phase coating comprises a first solid phase and a second solid phase, with the first solid phase distributed within the second solid phase. The first solid phase is Ni, NiO, Al, or Zn; the second solid phase is a YSZ or MCrAlX alloy, where M represents Ni, Co, a NiCo alloy, or a CoNi alloy, and X represents a metallic element with stronger reducing power than Al. An example of an MCrAlX alloy is NiCrAlY.

[0030] The porosity of the porous wear-resistant sealing coating is preferably 40% to 70%.

[0031] The method for preparing the porous wear-resistant sealing coating of the present invention includes:

[0032] (1) Prepare a first powder, the first powder having a composite structure, the composite structure including a coated inner core and a coated outer shell covering the outer surface of the coated inner core, the coated inner core being oxidized and volatilized at a preset temperature, and the melting point of the coated outer shell being lower than the melting point of the coated inner core;

[0033] (2) The first powder and the second powder are thermally sprayed onto the substrate to form an initial coating; the thermal spraying method includes flame spraying and atmospheric plasma spraying.

[0034] (3) The initial coating is subjected to high-temperature oxidation in an oxygen-containing atmosphere and at a preset temperature. The core of the first powder is oxidized and evaporated at high temperature to form the porous wearable sealing coating.

[0035] Step (2) specifically involves: mixing the first powder and the second powder in a certain proportion to obtain a mixed powder, and then thermally spraying the mixed powder onto the substrate; or thermally spraying the first powder and the second powder onto the substrate separately at the same time.

[0036] In the jet formed by thermal spraying, the outer shell of the first powder melts or partially melts, while the second powder melts (e.g., ...). Figure 4 ) or unmelted (such as Figure 3 The powder is directed onto and deposited onto the substrate surface. The molten outer shell connects the inner core to the second powder and the substrate. Through repeated deposition, an initial coating is formed.

[0037] The outer shell of the first powder is a metal or other material with a melting point below 2100°C, and the inner core is a metal or other material with a melting point above 1500°C or significantly higher than the melting point of the outer shell.

[0038] The first powder is preferably coated with Ni, NiO, Al, or Zn; the particle size of the first powder ranges from 10 to 150 μm, preferably 10 to 50 μm, 50 to 100 μm, or 100 to 150 μm. The thickness of the coating shell is approximately 1 micrometer. The inner core is preferably Mo; the inner core can be a solid particle, a hollow particle, or an agglomerated particle. Figure 1 The diagram shows two cases: the inner core is made of solid particles and the inner core is made of aggregated particles.

[0039] The volume of the second powder accounts for 20-80% of the total volume of the first and second powders.

[0040] The high-temperature oxidation and heat preservation temperature is 600-800℃, oxidation is carried out in air, and the oxygen partial pressure is 1-100Pa.

[0041] Example 1

[0042] A first powder, with a particle size ranging from 50 to 100 μm, was prepared by electroless nickel plating to coat and sinter agglomerated Mo (molybdenum, melting point 2620 °C) with Ni (nickel, melting point 1453 °C). A second powder, consisting of 50% YSZ (yttrium-stabilized zirconium oxide, Y₂O₃-ZrO₂, melting point 2680 °C), was then added. Surface and cross-sectional photographs of the second powder are shown below. Figure 2 As shown, after uniform mixing, a porous, wear-resistant sealing coating was prepared by flame spraying. The flame gun used was an oxyacetylene powder gun. Oxygen was used for powder feeding at a feed rate of 3 r / min, acetylene flow rate of 7 L / min, spraying distance of 50 mm, a neutral flame, and compressed air flow rate of 30 L / min. The mixed powder was heated and accelerated to deposit onto the sandblasted nickel-based alloy substrate surface through flame spraying. The resulting coating was then held at 600℃ in air for 10 h, where molybdenum oxidized to molybdenum trioxide and volatilized, forming a porous, wear-resistant sealing coating with a porosity of 60%.

[0043] like Figure 5 The image shown is an SEM image of the coating prepared in this embodiment. It can be seen that there are many spherical pores in the coating. The coating obtained in this embodiment has a bonding strength of 25 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 6000. The porosity of the coating before wear is 44%, and the porosity of the cross section at the wear mark of the coating after wear is 46%, indicating that no surface densification has occurred. This achieves air passage sealing while protecting the blade tip from damage.

[0044] Example 2

[0045] A first powder, with a particle size ranging from 50 to 100 μm, was prepared by electroless nickel plating to coat sintered agglomerated Mo (molybdenum, melting point 2620 °C) powder with Ni (nickel, melting point 1453 °C). A mixed spraying method was used, employing both flame spraying of the first powder and atmospheric plasma spraying of the second powder (YSZ). The flame spray gun was an oxyacetylene powder gun, using oxygen for powder feeding at a flow rate of 7 L / min and a spraying distance of 50 mm. The flame was an oxidizing flame, and the compressed air flow rate was 30 L / min. Atmospheric plasma spraying used nitrogen for powder feeding at a feed rate of 3 r / min, a power of 36 kW, and a spraying distance of 120 mm. The two powders were simultaneously heated and deposited onto a pre-blasted nickel-based alloy substrate using the flame-atmospheric plasma mixed spraying method. The resulting coating was then held at 600 °C in air for 10 h, causing the molybdenum to oxidize into molybdenum trioxide, which then volatilized, forming a porous, wear-resistant sealing coating with a porosity of 54%.

[0046] The coating obtained in this embodiment has a bonding strength of 25 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 6000, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0047] Example 3

[0048] A first powder, with a particle size range of 50–100 μm, was prepared by chemical plating to coat sintered agglomerated Mo (molybdenum, melting point 2620 °C) with Zn (zinc, melting point 419.53 °C). 25% YSZ (yttrium-stabilized zirconium oxide, Y₂O₃-ZrO₂, melting point 2680 °C) powder was added and mixed thoroughly. A porous, wear-resistant sealing coating was then prepared by flame spraying. An oxyacetylene powder gun was used. Oxygen was used for powder feeding, with an acetylene flow rate of 7 L / min, a spraying distance of 50 mm, a neutral flame, and a compressed air flow rate of 30 L / min. The mixed powder was deposited onto a sandblasted nickel-based alloy substrate surface via flame spraying. The resulting coating was then held at 600 °C for 10 h in an oxygen atmosphere, where molybdenum oxidized to molybdenum trioxide and volatilized, forming a porous, wear-resistant sealing coating with a porosity of 48%.

[0049] The coating obtained in this embodiment has a bonding strength of 27 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 5000, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0050] Example 4

[0051] A first powder, with a particle size range of 50–100 μm, was prepared by chemical plating to coat sintered agglomerated Mo (molybdenum, melting point 2620 °C) with Zn (zinc, melting point 419.53 °C). A mixed spraying method was used, employing both flame spraying of the first powder and atmospheric plasma spraying of the second powder (YSZ). The flame spray gun was an oxyacetylene powder gun, using oxygen for powder feeding at a flow rate of 7 L / min, a spraying distance of 50 mm, an oxidizing flame, and a compressed air flow rate of 30 L / min. Atmospheric plasma spraying used nitrogen for powder feeding at a feed rate of 3 r / min, a power of 36 kW, and a spraying distance of 120 mm. The two powders were simultaneously heated and deposited onto a pre-blasted nickel-based alloy substrate using the flame-atmospheric plasma mixed spraying method. The resulting coating was then held at 600 °C for 10 h in an oxygen atmosphere, where molybdenum oxidized to molybdenum trioxide and volatilized, forming a porous, wear-resistant sealing coating with a porosity of 54%.

[0052] The coating obtained in this embodiment has a bonding strength of 27 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 5000, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0053] Example 5

[0054] A first powder, NiO (nickel oxide, melting point 1960–2000℃) coated with Mo (molybdenum, melting point 2620℃), with a particle size range of 50–100 μm, was prepared using mechanical methods. A second powder, 75% YSZ (yttrium-stabilized zirconium oxide, Y₂O₃-ZrO₂, melting point 2680℃), was added and mixed thoroughly. A porous, wear-resistant sealing coating was then prepared by flame spraying. An oxyacetylene powder gun was used. Oxygen was used for powder feeding, acetylene flow rate was 7 L / min, spraying distance was 50 mm, the flame was neutral, and compressed air flow rate was 30 L / min. The mixed powder was deposited onto a sandblasted nickel-based alloy substrate surface via flame spraying. The resulting coating was then held at 800℃ in air for 10 h, causing molybdenum to oxidize into molybdenum trioxide and volatilize, forming a porous, wear-resistant sealing coating with a porosity of 50%.

[0055] The coating obtained in this embodiment has a bonding strength of 23 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 4800, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0056] Example 6

[0057] A first powder, NiO (nickel oxide, melting point 1960–2000℃) coated with Mo (molybdenum, melting point 2620℃), with a particle size range of 50–100 μm, was prepared using mechanical methods. A mixed spraying process was employed, involving separate flame spraying of the first powder and separate atmospheric plasma spraying of a second powder, YSZ. The flame spray gun used was an oxyacetylene powder gun, with oxygen feeding, an acetylene flow rate of 7 L / min, a spraying distance of 50 mm, an oxidizing flame, and a compressed air flow rate of 30 L / min. Atmospheric plasma spraying used nitrogen feeding at a feed rate of 3 r / min, a power of 36 kW, and a spraying distance of 120 mm. The two powders were simultaneously heated and deposited onto a pre-blasted nickel-based alloy substrate surface through the flame-atmospheric plasma mixed spraying. The resulting coating was then held at 800℃ in air for 10 h, causing molybdenum to oxidize into molybdenum trioxide, which then volatilized, forming a porous, wear-resistant sealing coating with a porosity of 54%.

[0058] The coating obtained in this embodiment has a bonding strength of 23 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 4800, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0059] Example 7

[0060] A first powder, consisting of Ni (nickel, melting point 1453℃) coated with Mo (molybdenum, melting point 2620℃), with a particle size range of 50–100 μm, was prepared by electroless nickel plating. A second powder, consisting of 50% NiCrAlY alloy (melting point 1350℃), was then added and mixed thoroughly. A porous, wear-resistant sealing coating was then prepared by flame spraying. The flame spraying gun used was an oxyacetylene powder gun. Oxygen was used for powder feeding at a rate of 3 r / min, acetylene flow rate was 7 L / min, the spraying distance was 50 mm, the flame was neutral, and the compressed air flow rate was 30 L / min. The mixed powder was heated and accelerated by flame spraying, depositing onto the surface of a pre-blasted nickel-based alloy substrate. The resulting coating was then held at 800℃ in air for 10 h, causing the molybdenum to oxidize into molybdenum trioxide, which then volatilized, forming a porous, wear-resistant sealing coating with a porosity of 60%.

[0061] The coating obtained in this embodiment has a bonding strength of 25 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 6000, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0062] Example 8

[0063] A first powder, with a particle size ranging from 50 to 100 μm, was prepared by electroless nickel plating to coat a second NiCrAlY alloy powder with Mo (molybdenum, melting point 2620 °C). The first powder was coated using a flame alone, while a second NiCrAlY alloy powder was coated using atmospheric plasma. The flame spray gun used was an oxyacetylene powder gun, with oxygen feeding, an acetylene flow rate of 7 L / min, a spraying distance of 50 mm, an oxidizing flame, and a compressed air flow rate of 30 L / min. The atmospheric plasma spraying used nitrogen feeding at a feed rate of 3 r / min, a power of 36 kW, and a spraying distance of 120 mm. The flame-atmosphere-plasma mixed spraying method simultaneously heated and accelerated the deposition of both powders onto a pre-blasted nickel-based alloy substrate. The resulting coating was then held at 800 °C in air for 10 h, causing the molybdenum to oxidize into molybdenum trioxide, which then volatilized, forming a porous, wear-resistant sealing coating with a porosity of 58%.

[0064] The coating obtained in this embodiment has a bonding strength of 25 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 6000, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0065] Example 9

[0066] A first powder, Al (aluminum, melting point 660℃) coated with Mo (molybdenum, melting point 2620℃), was prepared by chemical plating. A second powder, consisting of 30% NiCrAlY alloy (melting point 1350℃), was added and mixed thoroughly. A porous, wear-resistant sealing coating was then prepared by flame spraying. The flame spray gun used was an oxyacetylene powder gun. Oxygen was used for powder feeding at a rate of 3 r / min, acetylene flow rate was 7 L / min, the spraying distance was 50 mm, the flame was neutral, and the compressed air flow rate was 30 L / min. The mixed powder was heated and accelerated by flame spraying, depositing onto a pre-blasted nickel-based alloy substrate. The resulting coating was then held at 800℃ in air for 10 h, causing the molybdenum to oxidize into molybdenum trioxide, which then volatilized, forming a porous, wear-resistant sealing coating with a porosity of 70%.

[0067] The coating obtained in this embodiment has a bonding strength of 25 MPa. During the wear process, the wear ratio between the blade tip and the coating is greater than 6000, and no surface densification occurs. While achieving air passage sealing, it protects the blade tip from damage.

[0068] The above provides a detailed description of a porous wearable sealing coating and its preparation method provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as limiting the claims of the present invention.

Claims

1. A method of making a porous abradable seal coat, characterized by, The porous abradable seal coating comprises a base phase coating and spherical-like pores uniformly distributed in the base phase coating, the spherical-like pores having a pore diameter of 10-150 μm; the base phase coating comprises a first solid phase and a second solid phase, the first solid phase being distributed in the second solid phase; The first solid phase is Ni, NiO, Al or Zn; the second solid phase is YSZ or NiCrAlY alloy; The method comprises: (1) preparing a first powder having a composite structure, the composite structure comprising a coated inner core and a coated outer shell coated on the outer surface of the coated inner core, the melting point of the coated outer shell being lower than the melting point of the coated inner core; the coated outer shell is Ni, NiO, Al or Zn; the coated inner core is Mo; (2) thermally spraying the first powder and a second powder on a substrate to form an initial coating; wherein, during thermal spraying, the coated outer shell of the first powder is completely or partially melted, and the coated inner core is not melted; the second powder is YSZ or NiCrAlY alloy; (3) oxidizing the initial coating in an oxygen-containing atmosphere at a preset temperature, the coated inner core being evaporated after oxidation to form the porous abradable seal coating.

2. The method of claim 1, wherein the porous abradable seal coating is prepared by In step (2), the volume of the second powder accounts for 20-80% of the total volume of the first powder and the second powder.

3. The method of claim 1, wherein the porous abradable seal coating is prepared by Step (2) specifically comprises: mixing the first powder and the second powder to obtain a mixed powder, and thermally spraying the mixed powder on the substrate; or separately thermally spraying the first powder on the substrate, and simultaneously, separately thermally spraying the second powder on the substrate.

4. The method of claim 1, wherein the porous abradable seal coating is prepared by In step (3), the preset temperature is 600-800 ℃.

5. The method of claim 1, wherein the porous abradable seal coating is formed by a process comprising: The porosity of the spherical-like pores in the base phase coating is 40-70%. The porous abradable seal coating comprises a base phase coating and spherical-like pores uniformly distributed in the base phase coating, the spherical-like pores having a pore diameter of 10-150 μm; the base phase coating comprises a first solid phase and a second solid phase, the first solid phase being distributed in the second solid phase; The first solid phase is Ni, NiO, Al or Zn; the second solid phase is YSZ or NiCrAlY alloy; The method comprises: (1) preparing a first powder having a composite structure, the composite structure comprising a coated inner core and a coated outer shell coated on the outer surface of the coated inner core, the melting point of the coated outer shell being lower than the melting point of the coated inner core; the coated outer shell is Ni, NiO, Al or Zn; the coated inner core is Mo; (2) thermally spraying the first powder and a second powder on a substrate to form an initial coating; wherein, during thermal spraying, the coated outer shell of the first powder is completely or partially melted, and the coated inner core is not melted; the second powder is YSZ or NiCrAlY alloy; (3) oxidizing the initial coating in an oxygen-containing atmosphere at a preset temperature, the coated inner core being evaporated after oxidation to form the porous abradable seal coating. In step (2), the volume of the second powder accounts for 20-80% of the total volume of the first powder and the second powder. Step (2) specifically comprises: mixing the first powder and the second powder to obtain a mixed powder, and thermally spraying the mixed powder on the substrate; or separately thermally spraying the first powder on the substrate, and simultaneously, separately thermally spraying the second powder on the substrate. In step (3), the preset temperature is 600-800 ℃. The porosity of the spherical-like pores in the base phase coating is 40-70%.

Images